Dori waldman android _course

Android Development
Dori Waldman

Overview
 Android Introduction
 Android Components (Activity, Intent, Fragment, Service, Broadcast receiver,
 Working with Resources
 Application Lifecycle (Activity,Service,Fragment)
 Working with Threads
 Service (local vs remote)
 Persistence
 Location
 Http/WS connection
 Security / permission model
 Hybrid development (phonegap/jquery mobile)
 Development/Test tools ()
 Native UI components (Toast…Widget)
2

ContentProvider…)

Course Resources
http://developer.android.com/

http://developer.android.com/training/index.html

http://www.xda-developers.com/category/android/
http://www.vogella.de/android.html

4

Introduction
•

•

5

In 2005 Google acquired startup company called
“Android” and released the code as an open
source.
In late 2007, Android become the chosen OS by
industry leaders such as : Sprint, T-Mobile,
Samsung, Toshiba

Native OS

Smart Phone definition ?
•
•

6

No standard (screen resolution / camera / GPS)
More than 30 vendors (HTC, Samsung , Firefox …)

Code Complicity
if (packageManager.hasSystemFeature(PackageManager.FEATURE_CAMERA)) {
Log.i("camera", "This device has camera!");
}else{
Log.i("camera", "This device has no camera!");
}
if ( android.os.Build.VERSION.SDK_INT >=
android.os.Build.VERSION_CODES.GINGERBREAD) {
// only for gingerbread and newer versions
}
GooglePlayServicesUtil.isGooglePlayServicesAvailable()
7

The Pain of Native UI , or why Hybrid is poplar ?
Same App on different devices/OS
2.3.4 Samsung

8

4.1 Samsung

Mobile Web Vs Desktop Web
•

9

Web site should fit both – one development effort

Mobile Web Vs. Desktop Web
•

Same functionality ?

No uploads

View pictures
taken nearby

10

Mobile Challenges (external app events)
•

•

Android OS might kill the application process in case
of non efficient resources therefore developer should
listen to OS events (onLowMemory() …) and
response to them (save the application data).
For example
• phone call during payment flow.
• device rotation – will restart the application
• lost internet connection during upload.

11

Major Android versions
•
•
•

12

2.3 -API Level: 9 (gingerbread)
3.0 -API Level: 11 (honeycomb) provide support for tablets
4.0 -API Level: 14 (ice cream sandwich)

OS learning curve :
Its not just New OS version , http://developer.android.com/google/play-services/index.html

•

New Features 

•

Code is changing quickly 
•

Between android 2-4 the way that we invoke background threads has been
changed 4 times

•

Map Api has been changed dramatically between version 1 and version 2

Those changes are not cosmetic, they allows to create better application: save
battery, avoid application crash.
13

Android is not only for Phones/Tablet/Tv

14

Stack

Linux Kernel provides hardware drivers, memory/power/network/security/thread management
16

File System
•

User application will be
located under data folder

•

Framework Application
will be located under
System/App folder

•

C++ libs will be located
under system/framework
folder

17

NDK
• Allows to develop parts of the application using native-code languages such as C and
C++
• http://developer.android.com/tools/sdk/ndk/index.html
• Android C++ framework:
– http://www.mosync.com/
– http://xamarin.com/monoforandroid

18

Android Artifact
•

Android executable “.apk” file (similar to war file).

•

Each app run in its own linux process

•

Java classes are being convert into Dalvik executable “.dex” file (corresponding to .jar
file) which are half size compare to jar file.

•

19

Reverse engineering : apk  dex  *.class files  java
• https://code.google.com/p/android-apktool/
• https://code.google.com/p/dex2jar/
• https://code.google.com/p/smali2java/

Android Tools
• AVD (create an run emulator)
• DDMS (monitor device/emulator)

• ADB (control device from CMD)
• Logcat
• AAPT (Android Asset Packaging Tool - create apk)
• SQLLite3
• TraceView/dmtracedump (analyze logs)
• ProGuard (shrink artifacts size)
• Monkey/MonkeyRunner – API to remote control device (automate test)

• Draw9Patch (utility to create scalable bitmap) , Pixel Perfect
• Lint (tool to app optimization)
• Hierarchy viewer / uiAutomatorViewer
• DX (convert java to dex)
• Mksdcard (external storage for emulator)
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• Hprof-conv (convert logs to preferred profile tool)

Main Components
Activity – Manage the business logic, UI flow, events and invoke services
Fragment – embedded inside activity, allows reusable UI elements
Service - background process, which has no user interface, used for long running
operation and also to expose functionality for external applications.

Content Provider - used to share data among applications without exposing the data
layer (for example retrieve contact list from database)
Broadcast – used to send events
Intent - used to invoke activity/service/broadcast
-----------------------------------------------------------------------------------------------------------------------View – UI component (Button, Text area …)
Layout – Composite View

21

Recommended way to develop UI

23

Build UI (Code / XML)
<LinearLayout xmlns:android=http://schemas.android.com/apk/res/android android:orientation="vertical"
android:layout_width="fill_parent“ android:layout_height="fill_parent">

<TextView android:text="@string/InsertName" android:id="@+id/textView1“
android:layout_width="wrap_content" android:layout_height="wrap_content">
</TextView>
<Button android:text="Button" android:id="@+id/button1“ android:layout_width="wrap_content"
android:layout_height="wrap_content">
</Button>
</LinearLayout>

LinearLayout linearLayout = new LinearLayout(this);
Button button = new Button(this);
linearLayout.addView(button);
setContentView(linearLayout);
24

Code Example
• EX1
– Create Application with 3 activities , 2 fragments
– Transfer data between activities using Intent / StartActivityForResult
– Transfer data between activity and its fragments using getActivity()
– Build UI programmatically/xml
– Using Shared Preferences to persist and transfer data
– Fragment Stack
– Activity Stack
– Open Activity Explicitly / Implicitly

25

Activity (Activity Stack)
•

Activity class takes care of creating a window for you in which you can place your UI
and interact with the user.

•

One application contains several activities which are managed in stack

•

Activity is a single, focused thing that the user can do, for example one activity will
show contact list, another activity will invoke a call to selected contact.

27

Activity State:
•

Active - The screen is foreground/focus

•

Pause - lost focus but is still visible (another activity has focus on top of this
activity), it maintains its state and remains attached to the window manager, but can be
killed by the system in extreme low memory situations.

•

Stop – Not visible to the user (cover by another activity) It still retains its state, it will
often be killed by the system when memory is needed elsewhere.

•

Finish – either by calling to finish() or when OS kill the process, When application
finished, it is actually cached until OS will free cached resources

28

Activity Lifecycle

http://developer.android.com/reference/android/app/Activity.html

onRestoreInstanceState

onSaveInstanceState

The entire lifetime
happens between
onCreate() – onDestroy()
The visible lifetime
happens between
onStart() - onStop().

The foreground lifetime
(focus) happens between
onResume() - onPause()
29

Activity Lifecycle - entire lifetime
onCreate() is called only once when the activity is created (~Constructor), use this method for:
• Initialize UI elements (findViewById(), setContentView(int) ),
• initialize resources (avoid the creation of short-term objects in several places)...
onCreate() /onRestoreInstanceState() methods are also used to restore UI state (if exist)

onDestroy() is called either because the activity is finishing (finish()) , or because the OS
destroying this instance of the activity to free resources (When OS kill the application this
step might not be invoked at all).
Use onDestroy() to clean up any resources which has been established in onCreate()
like close network/database connections.
30

Activity Lifecycle - visible lifetime
During this phase the user can see the activity on-screen, but its not at foreground/focus
and there is no interacting with the user.
The onStart() and onStop() methods can be called multiple times, as the activity get/lose
focus.
onStart() is called after onCreate, or after onRestart() (when user navigate back to the
activity)
onStop() is called when the activity becomes invisible to the user.
Use this method to :
Suspend all resources which are being used to update the user interface as in this
phase the activity is not visible to the user
For example suspend threads, stop animation, unregister to Broadcast Receivers, stop
GPS, unbind services…
31

Activity Lifecycle – foreground/focus lifetime
During this phase the Activity is in focus and user interact with it.
Activity can frequently go between the OnResume() and onPause() states (device went to
sleep) therefore code between these methods should be kept lightweight.
OnResume() At this point activity is at the top of the activity stack.

onPause() will be invoked when activity is not in focused,
• It‟s the last safe point, after this point Activity may be killed without continue
to onStop() therefore you should use this point to persist user changes.
From onPause() , either OnResume() or onStop() will be invoked.

32

OnSaveInstanceSave()– onRestoreInstanceState()
• OS default behavior save the state of an activity in memory when it is stopped.
This way, when users navigate back to a previous activity, the view appears the
same way the user left it.
• The default implementation calls the corresponding onSaveInstanceState() method for
every View in the layout (only if for views with android unique id) and saves the views
state in Bundle : onCreate(Bundle) /onRestoreInstanceState(Bundle)
• For all other cases you need to save and restore the UI state via onSaveInstanceState()
• onRestoreInstanceState(Bundle) will be called by OS only if OS killed the application
and restart it again.

33

Activity A Start

INFO/EX1-A (406): onCreate Begin
INFO/EX1-A (406): onCreate End
INFO/EX1-A (406): onStart Begin
INFO/EX1-A (406): onStart End
INFO/EX1-A (406): onResume Begin
INFO/EX1-A (406): onResume End

Example of Activity lifecycle – Demo EX1
Click on a button
And open activity B

click on “Close“ and return to
First Activity

34

INFO/EX1-A (406): onSaveInstanceState Begin
INFO/EX1-A (406): onSaveInstanceState End
INFO/EX1-A (406): onPause Begin
INFO/EX1-A (406): onPause End
INFO/EX1-B (406): onCreate Begin
INFO/EX1-B (406): onCreate End
INFO/EX1-B (406): onStart Begin
INFO/EX1-B (406): onStart End
INFO/EX1-B (406): onResume Begin
INFO/EX1-B (406): onResume End
INFO/EX1-A (406): onStop Begin
INFO/EX1-A (406): onStop End
INFO/EX1-B (406): onPause Begin
INFO/EX1-B (406): onPause End
INFO/EX1-A (406): onRestart Begin
INFO/EX1-A (406): onRestart End
INFO/EX1-B (406): onStop Begin
INFO/EX1-B (406): onStop End
INFO/EX1-B (406): onDestroy Begin
INFO/EX1-B (406): onDestroy End

Activity „A‟ started
Example of Activity

lifecycle (Ex1)

Get phone call, OS Destroy the Activity

Hung up and unlock
Phone, back to app

35

INFO/EX1-A (406): onSaveInstanceState Begin
INFO/EX1-A (406): onSaveInstanceState End
INFO/EX1-A (406): onPause Begin
INFO/EX1-A (406): onPause End
INFO/EX1-A (406): onStop Begin
INFO/EX1-A (406): onStop End
INFO/EX1-A (406): onRestart Begin
INFO/EX1-A (406): onRestart End
INFO/EX1-A (832): onRestoreInstanceState Begin
INFO/EX1-A (832): onRestoreInstanceState End

Activity Configuration
*configChanges attribute prevent
application from restart (rotate)

http://developer.android.com/guide/t
opics/manifest/activity-element.html

36

Task – Task Stack (Home Button)
• Task is a collection of activities that users interact with when performing a certain job
(~application)
• When the user leaves a task by pressing the Home button, the current activity is
stopped and its task goes into the background.
• The OS retains the state of every activity in the task. If the user later on resumes the
task by selecting the launcher icon that began the task, the task comes to the
foreground and resumes the activity at the top of the stack.
• For example open SMS app and write SMS , Click on Home button and start another
app, close that app , long click on Home button and select the SMS app , you will see
the text that you started to wrote.

Task B receives user interaction in the
foreground, while Task A is in the background,
waiting to be resumed.
37

Fragment
• Divide Activity to reusable components, each has its own lifecycle (onCreate()…)
• Fragment is tightly coupled to activity in which its placed, therefore when the activity is
stop/pause/destroy the fragments are also stop/pause/destroy.
• Fragments are also managed in a stack
• Fragment can be added/removed several time during activity lifetime
• Its possible to create without any UI
• For backward compatibility you should extends “FragmentActivity” instead of Fragment”

39

Fragment Lifecycle
OnAttach – bound to activity , get reference to parent activity
onCreate – initialize fragment resources not UI !
onCreateView – initialize fragment UI (like activity onCreate)
onActivityCreated – a callback that parent activity is ready , incase the
fragment UI depend on parent activity UI, use to initialize Frag UI here
onStart – visible
onResume – focus
onPause – end of focus
onSavedInstanceState
onStop – end of visible
onDestroyView – Fragment View is detached , clean UI resources
onDestroy – clean resources , end of life
onDetach – Fragment is detach from activity, if parent activity will be killed,
this step will not be called
40

Static way to add fragment
<linearLayout>
<!– FragA is a class that extends Fragment - ->
<fragment android:name=“com.dori.FragA”/>
</linearLayout>

41

Dynamic way to add fragment (Frag container)
<linearLayout>
<FrameLayout android:id=“FragContainer” />
</linearLayout>
FragmentTransaction ft = fragmentManager.beginTransaction();
Fragment frag = Ft.findFragmentById(R.id. FragContainer)
ft.remove(frag);
ft.add(R.id. FragContainer, MyFragB);
ft.addToBackStack(“tag”);
ft.commit();

42

Fragments for both Tablet / Phones
• Each activity will convert into fragment meaning:
– Create new fragments and move the activities code into it , the original activity will act as a
container for the fragment.
• Create 2 kinds of layouts, the OS will select the layout according to screen size.
– One layout in layout-land folder for tablet view with fragA_layout.xml
– layout per fragment fragA_layout.xml and fragB_layout.xml
• Each fragment will be created in a separated activity , Activity B is never used on a tablet. It is simply
a container to present Fragment B.
• When you need to switch Fragments, activity A checks if the second fragment layout is available in
his layout:
– If the second fragment is there, activity A tells the fragment that it should update itself.
– If the second fragment is not available activity A starts the second activity.
43

Work with Fragments
• working with fragments
• http://www.vogella.com/articles/AndroidFragments/article.html
• http://developer.android.com/guide/practices/tablets-and-handsets.html

45

Fragment recreation
• When activity is being destroyed and restart (Rotate) you can select that the fragment
will not be restart with its associate activity, by calling setRetainInstane(true) from the
Fragment onCreate()
• In that case The Fragment onDestroy() onCreate() will not be called while the attached
activity is being destroyed-created , All other Fragment lifecycle methods will be invoked
like onAttach…., therefore moving most of the object creation to onCreate will improve
the performance

46

Intent
• Intent is used to invoke activity/service/broadcast
– More Intents components will be explained later:
• PendingIntent
• ServiceIntent
• Broadcast Intents
• There are 3 ways to invoke activity:
Intent intent = new Intent(MyActivity.this, AnotherActivity.class);
Intent.putExtra(“someLabel”, “someValue”);
startActivity(intent);

48

Second way to invoke Intent:
Intent intent = new Intent();
intent.setComponent(
new ComponentName(
"com.android.contacts“,
"com.android.contacts.DialContactsEntryActivity“
);
startActivity(intent)

49

Third way to invoke intent - Late Runtime Binding
This example will start dialer activity and will make a call
Intent intent = new Intent(Intent.ACTION_DIAL, Uri.parse(“tel:52325”));
Action

Data -optional

While this intent will only open dialer application
new Intent(Intent.ACTION_DIAL);

Late Runtime Binding means that Android at run time resolve the class that will perform
the action, it can be different class deepened on the type of data specified (will be
explained later)

50

Activity Callback:
• In order to get response back from sub activity, invoke startActivityForResult and
provide activity Id:
Intent intent = new Intent(this, SubAct.class);
Int subActId = 1;
startActivityForResult(intent, subActId );
• Before sub-Activity is closed, call setResult to return a result(as intent) with status to
the calling Activity.
Intent myIntent= new Intent();
myIntent.putExtra("somethingBack",”someValue”);
setResult(RESULT_OK, myIntent);
finish();

51

Activity Callback:
• When a sub-Activity closes, callback method will be invoked in the parent activity
onActivityResult

public void onActivityResult(int requestCode,int resultCode,Intent data) {
switch(requestCode) {
case (subActId) : {
if (resultCode == Activity.RESULT_OK) {
data.getStringExtra(“somethingBack”)
…

52

Logs – callback is called before activity closed
•
•
•
•
•
•
•
•
•
•
•
•

53

INFO/B (2673): onBackPressed start
INFO/B (2673): saveBeforeClose begin
INFO/B (2673): editText.getText()=hi
INFO/B (2673): saveBeforeClose end
INFO/B (2673): onBackPressed end
INFO/B (2673): onPause start
INFO/B (2673): onPause end
INFO/A (2673): onActivityResult --- callback
INFO/B (2673): onStop start
INFO/B (2673): onStop End
INFO/B (2673): onDestroy start
INFO/B (2673): onDestroy end

Adding & Retrieving data from intent
Intent.putExtra(String name, boolean value); //simple value

Intent.putExtra(String name, int[] values); // simple array
Intent.putParcelableArrayListExtra(String name, ArrayList arrayList);
Intent.putExtra(Bundle bundle) // Bundle is a key-value map

Intent.putSerilaizable()
If you're just passing objects use Parcelable , It requires a little more effort to use than
using Java's native serialization, but it's way faster (and I mean way, WAY faster).

intent.getExtras();

54

Intent Filters
• Intent Filters are used to register Activities, Services, and Broadcast Receivers, if the
intent filter attributes “match” the calling Intent (will be explained later) the action will be
invoked, for Example AppA will invoke AppB:
Intent intent = new Intent(“com.dori.AnotherActivity”); // Late Runtime Binding (like open camera)
-------------------------------------------------------------------------------------------------<activity android:name=“SomeActivity“>
// In AppB Manifest
<intent-filter>
<action android:name="com.dori.AnotherActivity"/>
<category android:name="android.intent.category.DEFAULT" />
<data …. />
</intent-filter>
</activity>
-----------------------------------------------------------------------------------------55
 AppB will be open and , SomeActivity will be invoked

How does android know which Intent to invoke ?
• Android collect all the Intent Filters available from the installed apps, Intent Filters that
do not match the action or category associated with the Intent being resolved are
removed from the list.
• If the class name attached to an intent (explicit), then every other aspect or attribute of
the intent is ignored and that class will be execute, no need to continue to match the
intent data.
• Otherwise we need to have a full match of action+data+category

56

Sticky Intent
A normal Broadcast intent is not available anymore after is was send and processed by
the system.
Android system uses sticky Broadcast Intent for certain system information like battery
changes,
The intent which is returned is Sticky meaning that it keep available, so clients can
quickly retrieve the Intent data without having to wait for the next broadcast, the
clients no need to register to all future state changes in the battery.

Sticky broadcasts are used by android to send
device state, they are heavy on the system ,
don‟t use them if you don‟t need.

57

unregister Receiver

Send Sticky Intent
Intent intent = new Intent("some.custom.action");
intent.putExtra("some_boolean", true);
sendStickyBroadcast(intent);
….
removeStickyBroadcast(Intent intent)

58

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.dori" android:versionCode="1“ android:versionName="1.0">
<application android:icon="@drawable/icon" android:label="@string/app_name">
<activity android:name=".MyAct" android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<service android:name=".MyService"></service>
//Content Provider
<provider android:permission=”com.paad.MY_PERMISSION”
android:name=”.MyContentProvider”
android:enabled=”true”
android:authorities=”com.paad.myapp.MyContentProvider”/>
//Broadcast reciver

<receiver android:enabled=”true” android:label=”My Broadcast Receiver” android:name=”.MyBroadcastReceiver”/>
//uses-permission tags declare the permissions you‟ve determined that your application needs for it to operate properly. The
permissions you include will be presented to the user, to grant or deny, during installation
<uses-permission android:name=”android.permission.ACCESS_LOCATION”/>
// adding restrict access to an application component, Other applications will then need to include a uses-permission tag in their
manifests before they can use these protected components
<permission android:name=”com.paad.DETONATE_DEVICE” android:protectionLevel=”dangerous”
Destruct” android:description=”@string/detonate_description”/>
</application>
60
</manifest>

android:label=”Self

Manifest (~web.xml)
•
•
•
•
•
•
•
•
•

61

Uses-sdk : which android version are being supported
Uses-configuration : like application require finger touch
Uses-feature : hardware feature like NFC
Uses-permission : security model
Permission : security model
Instruments : testing framework (provides hook to the tested class)
Support-screens : (small …Xlarge)
Used library
Application (one per manifest)
– Activity
– Service
– Content provider
– Broadcast receiver

Application Class
• One per application
• Custom Application:
Class MyApp extends Application{
}
And in manifest : <application android:name=“.MyApp” …>
Usage : focal point to handle events like
onLowMemory,
create HttpClient,
ACRA (catch app exception)

62

Android Project Folder
• Src - A folder containing application source files
• Gen – Generated folder, don‟t touch.

• Assets – resources which are not generating ID (will be explained later),
assets directory can be used to store any kind of data.

64

• Res – A parent folder containing the resources of the application, most of the resources
are xml descriptors files.
– Values - A folder containing resources like
• strings,
• colors, <color name=“mycolor”>#0000000</color>
• dimensions (best practice use dp or sp) <dimen name=“ex1”> 16dp </dimen>
• Style
– Drawable - A folder containing the images or xml image-descriptor files.
– layout – In order to provide different layouts there is a need to create specific folders
for each configuration
– xml - A folder containing additional XML files used by the application.
– raw - A folder containing non xml data like audio/video files, android compiles into
binary format all the resources except the raw resources which are copied as-is
into the final .apk file
– Menu - A folder containing XML-descriptor files for the menus
– Anim - A folder containing XML-descriptor files for the animations.
65

localization
• Use folders to support localization, orientation …. :
• reslayoutmain_layout.xml
• reslayout-landmain_layout.xml
• reslayout-carmain_layout.xml //docking type
• resvaluesstrings.xml
• resvalues-enstrings.xml

66

Resources per resolution/screen size
Layouts:
Res/layout-long-land // long screen in landscape mode
Res/layout-w600dp // screen width is 600 dp
Res/layout-small // before android 3.2
Images folders:
Res/drawable-ldpi – low density for screen with 120dpi
Res/drawable-mdpi –for screen with 120dpi
Res/drawable-tvdpi –213 dpi
Res/drawable-hdpi – low density for screen with 240dpi
Res/drawable-xhdpi – low density for screen with 320dpi
Res/drawable-nodpi – force no scale regardless the device screen size
67

Working with resources
• Android inject the resource value at run time
(in /res/values/strings.xml)
<string name=“NewWindow">myText</string>
(In /res/layout/main.xml)

<Button android:id="@+id/button2 “ android:text="@string/NewWindow“ />
• Android generate Id for each resource in R.java:
public static final int button2=0x7f060004;
public static final int NewWindow=0x7f040005;
• Getting resources via code(activity)
Button button = (Button)findViewById(R.id.button2)
String myAppName = getResources().getString(R.string.app_name);
68

Resources Types:
• "@+id/editText1“ :
my application resource , (+) means that this is a new resource ,
getString(R.string. editText1)
• "@android:id/button1“ , android:src="@android:drawable/star_big_on“:
Android resource, getString(android.R.string. button1)
• ?android – theme support like <color:textcolor=“?android:textcolor”/>

69

Working with Assets
AssetManager used to manage “Assets” resources
AssetManager am = activity.getAssets();
InputStream is = am.open("test.txt");

70

Application metadata files
Both files are generated by android
proguard.cfg / proguard-project.txt - Java class file shrink, optimizer
default.properties – parameters like android version

72

Why Threads are important
• By default the all androd components runs on the main thread (UI thread)
– Activity
– Service
– ContentProvider
– BroadcastReciver

• If any action takes more than 5 seconds, Android throws an ANR message.
• In order to solve this we must manage time consuming action in a separated thread

74

Thread
Thread thread = new Thread(null,doInBackground,”background”);
Runnable doInBackground = new Runnable(){
public void run(){
myBackgroundProcess();
}
Q- How can I update the Main thread ?

75

Thread MQ
• Click on a button component is “translate”
into a message which is being dropped on
to the main queue.
• Main thread listen to the main Q and
process each incoming message.
• Handler are used to drop messages on the
main queue usually from a separate thread.

http://www.aviyehuda.com/blog/2010/12/20/android-multithreading-in-a-ui-environment/

• Message also holds a data structure that
can be passed back to the handler
Understand looper:
http://mindtherobot.com/blog/159/android-guts-intro-to-loopers-and-handlers/
http://kurtchen.com/blog/2010/08/31/get-to-understand-handler-looper-and-messagequeue/
76

Handler/Looper (message loop for a thread)
• Looper is a class that turns a thread into a Pipeline Thread (Q)
• Handler gives you a mechanism to push tasks into it from any other threads.
–

–

Each Handler instance is associated with a single thread (actually with that thread message queue)
this is done during the handler creation and initialization.

–

77

A Handler allows you to send and process Message and Runnable objects associated with a
thread's MessageQueue.

When the main thread retrieves messages, it invokes the handler that dropped the message
through a callback method “handleMesage” on the handler object.

Working with Threads
• Create a handler in the main thread.
• Create a separate thread that does the actual work. and pass it the handler
• The separate thread can do the work for longer than 5 seconds, and to send messages
to the main thread by the handler.
• The messages get processed by the main thread
• The main thread will invoke the handler callback methods (the message holds reference
to the handler)

78

private Handler handler = new Handler(){ //in the main thread create Handler object

Handler

@Override
public void handleMessage(Message msg){ // main thread will response to the handler callback
m_ProgressDialog.setTitle(msg.getData().getString("messageLabel")); // run in main thread

m_ProgressDialog.show();
}
};
Private Thread thrd = new Thread(){ // in the main thread, create another thread and pass it the handler
public void run(){ // BackgroundProcess - This code run in a separate Thread

doSomeLengthyWork();
Message message = handler.obtainMessage();
Bundle bundle = new Bundle();
bundle.putString("messageLabel", "thread finished");
message.setData(bundle);
handler.sendMessage(message); // send message to the main Q (handler.postAtTime())
handler.post(updateUIRunnable); //postDelay / postAtTime
}
thrd.start();
Private Runnable updateUIRunnable = new Runnable(){
public void run(){
updateUI(); // This Code run in the main thread
}

79

}

HandlerThread
Start a new thread that has a looper, The looper can then be used to create handler classes
Public class MyClass implements android.os.Handler.Callback
Public void dummy(){
// Create and start the HandlerThread - it requires a custom name
HandlerThread handlerThread = new HandlerThread("MyHandlerThread");

handlerThread.start();
Looper looper = handlerThread.getLooper(); // Get the looper from the handlerThread
Handler handler = new Handler(looper, this);
handler.post()  will send the to the HandlerThread Q instead of Main Q
handler.sendMessage()  will send the to the HandlerThread Q instead of Main Q
handlerThread.quit(); // Tell the handler thread to quit
}

@Override
public boolean handleMessage(Message msg) {
…. // run in HandlerThread

80

}

Working with Thread API
• handler - main thread getting updated by “handleMessage” callback method.
• runOnUiThread - update the main thread, from a sub thread.

• AsyncTask (android 2.2) manage the creation of the background thread and update the
main thread using “onPostExecute” callback method.
– AsyncTask are not persist across activity restart meaning that in case device has been
rotate the activity will be destroyed and restart and the asyncTask will be canceled,
therefore its recommended to start service and in that service to run asyncTask.
• AsyncTaskLoader (android 3.0) – improve AsyncTask (data was lost
across Activity configuration changes, each time the activity returns from a stopped state
an refresh data call has been invoked).
• http://www.androiddesignpatterns.com/2012/07/loaders-and-loadermanager81 background.html

runOnUiThread
• Thread thread = new Thread(new Runnable() {
public void run() {
// ...
// do long running tasks here
// …
// running in Activity context
runOnUiThread(new Runnable() {
public void run() {
// ...
// update UI here
// ...
}
});

}
});
thread.start();
82

AsyncTask
public void useTask() {
new FooTask().execute("param1", "param2");
}
<input param, progress param, result param>

class FooTask extends AsyncTask<String, Integer, Long> {
protected Long doInBackground(String... params) {
publishProgress(progress); // do long running tasks here in a separate thread
return result;
}
protected void onProgressUpdate(Integer... progress) {
// update progress to UI
}
protected void onPostExecute(Long result) {
myTextView.setText(resault); // update UI here
}
}
83

Run AsyncTask
• Asynctask can be execute only once ( if you will try to run again you will get exception) meaning:

new DownloadFilesTask().execute(url1, url2, url3);
new DownloadFilesTask().execute(url4, url5, url6);
you can NOT do the following:
DownloadFilesTask dfTask = new DownloadFilesTask();
dfTask().execute(url1, url2, url3);
dfTask().execute(url4, url5, url6);

84

Loader (AsyncTaskLoader)
• Loaders are responsible for
– performing async tasks on a separate thread,
– monitoring the data source for changes, and delivering new results to a registered
listener (usually the LoaderManager) when changes are detected.
• Loader available within any activity/fragment via LoaderManager

• AsyncTaskLoader, CursorLoader (will be explained later).
• http://developer.android.com/reference/android/content/AsyncTaskLoader.html

85

Use Loader
Activity/Fragment can implements LoaderCallbacks<T>
From Activity.onCreate() or Fragment.onActivityCreated() call to
getLoaderManager().initLoader(LOADER_ID like „0‟, args, this or
callback);
After loader has been created, calling initLoader again will
return the existing object, use restartLoder in order to recreate loader object (use it in case the query parameters
has been change)
public Loader<T> onCreateLoader –
use to create loader

public void onLoadFinished(Loader<T> loader, T data) –
update UI like textView.setText(data);
public void onLoaderReset(Loader<T> loader) –
will always be invoked when you leave the activity, release
reference to the data that was returned , also reset UI like
setText(null)
86

Create Custom Loader- Observer
Loaders should implement an observer in order to monitor the underlying data changes.
When a change is detected, the observer should call Loader.onContentChanged(),
which will either:
• force a new load if the Loader is in a started state
• raise a flag indicating that a change has been made so that if the Loader is ever
started again, it will know that it should reload its data.

http://www.androiddesignpatterns.com/2012/08/implementing-loaders.html

87

Class myLoader extends AsyncTaskLoader<T>
onStartLoading():
First method which is being invoked,
should invoke forceLoad()
In this method you should register Observesr

loadInBackground()
run in a background thread

deliverResult()
Called when there is new data to deliver to the client.
The Observers will invoke myLoader.onContentChanged()
correspond to data changes

88

Loader states:
Any given Loader will either be in a started, stopped, or reset state
• Loaders in a started state execute loads and may deliver their results to the
listener at any time. Started Loaders should monitor for changes and perform new
loads when changes are detected. Once started, the Loader will remain in a started
state until it is either stopped or reset. This is the only state in which onLoadFinished will
ever be called.
• Loaders in a stopped state continue to monitor for changes but should not deliver
results to the client. From a stopped state, the Loader may either be started or reset.

• Loaders in a reset state should not execute new loads, should not deliver new
results, and should not monitor for changes. When a loader enters a reset state, it
should invalidate and free any data associated with it for garbage collection (likewise,
the client should make sure they remove any references to this data, since it will no
longer be available).
89

Service:

• Services are background process, which has no user interface, they are used for long
running operation and also to expose functionality for external applications.
• you can update UI from service via notification/toast
• A Service is not a thread (Services by default are running on the main thread , just open a
service for long time action is not enough, you must open a thread inside)

• Services run with a higher priority than inactive or invisible activities and therefore it is less
likely that the Android system terminates them.
• Service which is bound to a focus activity or labeled as run in the foreground will almost
never be killed – recommended not to use this option
• If the system kills your service, it restarts it as soon as resources become available again,
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you must design it to gracefully handle restarts by the system, depand on the service type !!!

Lifecycle

• There are 2 kinds of services:
– Started (local)- send & forget
• starts it by calling startService(),
• The service will run until the service or someone
else explicitly stop it stopService() or stopSelf()
has been called, or in case OS need to release
resources, in that case OS will restart the service.
– Bound (Remote) –
• starts it by calling bindService(), does not call
onStartCommand()
• return a reference onBind() to the service, which
allows to invoke the service methods from
another class
• Can expose methods (aidl) to other applications.
• bound service runs only as long as another
application component is bound to it, When all
clients disconnect, or unbind, Android will stop
92
that Service.

Start Service
•

Start by calling
–

startService(new Intent (this,MyService.class);

–

startService (new Intent (MyService.PLAY_MUSIC));

•

Finish by calling
–
–

•

stopService() from the activity
stopSelf() from the service class
onCreate() will be invoked only once !

(first lunch or after OS restart it)
•

OnBind might return instance or null

•

onStartCommand() - this is where you will open a worker thread, called whenever a
client calls startService()

•

Calling startService() after the service has been started (meaning while it‟s running) will
not create another instance of the service, but it will invoke the service‟s
onStart()/onStartCommand() method again not the onCreate(),

93

Start service Flags– Restart The Service
onStartCommand() return a flags:
–

–

94

Service.START_STICKY – (DEFAULT)
• If the service killed by OS, it will restart when sufficient resource will be
available again, OS recreate the service and call onStartCommand() with a null
intent, unless there were pending intents to start the service, in which case,
those intents are delivered.

Service.START_NOT_STICKY
• OS will not automatically restart the service, the service will restart only if there
are pending StartService calls.
• use it in case your service can be stopped and start later in next scheduled interval

Start service Flags– OS Restart The Service
onStartCommand() return a flags:
–

Service.START_REDELIVER_INTENT
• if OS terminate the service it will be restart only if there are pending start calls or in
case the process end before the service called to stopSelf().
• Use it when its important to know that the service task has been finished property.

After OS restart the service the passed intent will be:
• null in case of START_STICKY
(unless there are pending startService calls)
• original intent in case of START_REDELIVER_INTENT
95

Start service - IntentService
A subclass of Service which open a worker
thread to handle all start requests ,
one at a time (Q not async not parallel like
Service)
–

The onHandleIntent() - use this method to
execute the background task , no need to
create a new thread.

–

After all received intent has been processed
(onHandleIntent() returns) the service is
destroyed. (no need to implement
onStartCommand or onDestroy)

96

This is the best option if you don't
require that your service handle multiple
requests simultaneously.
You cant use stopService() or stopSelf()
The IntentService is built to stop itself
when the last Intent is handled
by onHandleIntent(Intent).

Start Service after Device Reboot (not bind service !)
<manifest xmlns:android=http://schemas.android.com/apk/res/android package="com.Test">
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>
<application>
<receiver android:name=".BootCompletedIntentReceiver">
<intent-filter>
<action android:name="android.intent.action.BOOT_COMPLETED" />
</intent-filter>
</receiver>
<service android:name=".BackgroundService"/>
</application>
</manifest>
public class BootCompletedIntentReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
if ("android.intent.action.BOOT_COMPLETED".equals(intent.getAction())) {

Intent pushIntent = new Intent(context, BackgroundService.class);
context.startService(pushIntent);
}
97
}

Getting response from start service
Updated from services will be usually using broadcast mechanism (next section)
–

BroadcastReceiver – send/get data/notifications across applications, whenever you
send broadcast its sent system wide

–

LocalBroadcastRecevier / ResultReceiver – send/get data internal to application,
Your application is the only receiver of the data

•
•

98

http://www.sohailaziz.com/2012/05/intentservice-providing-data-back-to.html
http://www.vogella.com/articles/AndroidBroadcastReceiver/article.html

Bind Service (RemoteService= Service in a different process)
•

support a Remote Procedure Call (RPC) mechanism to allow external app‟s, on the
same device, to connect to the service

•

onBind() must return instance to the service object

•

Bind service ~ the service is like a member in your app

AIDL allows to transfer objects across process‟s (~intent)
•

Android Interface Definition Language is used in order to define the service to other
applications

•

AIDL allows you to pass java primitive (char,int) , String, List, complex types
(percable)

•

Create AIDL file in src folder, android will generate class from the aidl file (~stub)

99

Bind Service

RemoteCallbackList:
"If a registered callback's process goes away, this
class will take care of automatically removing it
from the list. If you want to do additional work in
this situation, you can create a subclass that
100
implements the onCallbackDied(E) method."

Reconnect bind service after service crush
• onServiceDisconnected –
Called when a connection to the Service has been lost. This typically happens when the process
hosting the service has crashed or been killed.
This does not remove the ServiceConnection itself , binding to the service will remain active.
Local Service:
run in the same process of the application (if app is closed the service will be closed as well) cant
reconnect !
Remote Service: Service is running in separate process, when this process has crashed or been
killed, only the actual service is destroyed, the activity lives in another process that bound to the service
is remained, therefore you can reconnect to existing service

101

Remote Service Consumer – client (RemoteServiceClient)
•

Copy the AIDL file to the client application (in same package like in the service
application

•

Use bindService() and not startService() in order to invoke the service

•

you cant assume that after calling to bindService() the service will be available !!!
bindService() is asynchronous.

•

When the connection to the service is established, the onServiceConnected() callback
is invoked

•

onServiceDisconnected() callback does not get invoked when we unbind from the
service, It is only invoked if the service crashes.

• http://manishkpr.webheavens.com/android-aidl-example/

102

Bind Service new flags
• BIND_ADJUST_WITH_ACTIVITY- set the service priority according to the bound activity
• BIND_ABOVE_CLIENT / BIND_IMPORTANT – set the priority to as forground
• BIND_NOT_FORGROUND

103

Service – Process
<service android:name="MyService" android:icon="@drawable/icon“
android:label="@string/service_name" android:process=":my_process" >
</service>
• Usually you will not add android:process, unless the service is remote
(android:process=":remote“)
• Running a service in its own process gives it its own memory address space and a garbage
collector of the virtual machine.
• Even if the service runs in its own process you need to use asynchronous processing
(Thread) to perform network access.

104

Mixed Service (Start & bind service)
• Implements both: onStartCommand() to allow components to start it and onBind() to
allow binding.
• Mixed mean that OS will keep the service running as long as its not explicitly stopped or
there are no client bound to it.
• The hybrid approach is very powerful and common way to use Services:
let‟s say we are writing an app that tracks user location.
We might want the app to log locations continuously for later use, as well as display
location information to the screen while the app is in use.
If you will only bind the service during application launch, you will get the
location update, but when the application will close the service will be destroyed
as well  , therefore you should also use start service approach in order to verify
that the server will remain running until it will explicitly close. 
105

Block UI thread ?
The Service will block the calling Activity until the service is started
• The best way in this case is to start a new thread and then call a service from there.
• Intentservice is a another solution

106

Summary:

• Start service - can be restart by OS , can be started after reboot, pay attention to onCreate(), onStartCommand()

107

Service – External Permission
• “android:exported = false” determine whether or not other applications can invoke the
service or interact with it.
• like an activity, a service can define intent filters which allow other components to
invoke the service using implicit intents, If you plan on using your service locally (other
applications will not be able to use it), then you should not add intent Filters
• android:exported Default value is false if there are no intent filter, and true if there are.

• There are more flags like : FLAG_GRANT_READ_URI_PERMISSION

109

Set service as Foreground
• Start service can set its priority as foreground by calling
startForeground(notification_id,notification) – foreground services are expected to have
interaction with the user (like player service)
– This is not recommended as the OS will not kill the service and will make it hard to
recover from resource starvation situations.
• bindService(intent,connection,Flag) can use its flag to set its priority like
BIND_IMPORTANT which is similar to Forground
• If there are clients bound to the service, and one of its clients is visible to the user, then
the service itself is considered to be visible.

110

Toast from a Thread in a service
Toast can be shown only from UI Thread (Main Thread)

111

links
• http://docs.xamarin.com/guides/crossplatform/application_fundamentals/backgrounding/part_7_android_services
• http://stackoverflow.com/questions/8668125/android-how-bound-service-can-be-noticed-about-killedclient
• http://developer.android.com/reference/android/app/Service.html
• http://developer.android.com/guide/components/services.html

112

WakeLock & Service
• In case device is sleeping (screen not in use) and service needs to restart ,it require the
device to be a wake
//acquire a WakeLock:
PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
PowerManager.WakeLock wakeLock = pm.newWakeLock(pm.SCREEN_DIM_WAKE_LOCK, "My wakelook");
// This will release the wakelook after 1000 ms
wakeLock.acquire(1000);
// Alternative you can request and / or release the wakelook via:
// wakeLock.acquire();
wakeLock.release();

114

Another way
Wake from activity
• getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
•
myActivity.getWindow().addFlags(
WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED
| WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON
| WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD);
• http://michael.theirwinfamily.net/articles/android/starting-activity-sleeping-device

https://github.com/commonsguy/cwac-wakeful (WakefulIntentService )
http://developer.android.com/reference/android/os/PowerManager.WakeLock.html

115

Receiver:
Android support event-driven application:

•

Sender Application call to sendBroadcast(intent) which is asynchronous

•

applications can register to those intents or system events (SMS,Low memory) by
extending BroadcastReceiver

•

We should avoid long running tasks in Broadcast receivers. For any longer
tasks we can start a service from within the receiver.

•

Broadcast are used to restart service after device reboot, update activity from a
service

•

Security - Make the broadcast receiver unavailable to the external applications using
android:export=”false”. Otherwise other applications can abuse them.

Types:
–
117

BroadcastReceiver – send data/notifications across system wide applications,

–

LocalBroadcastRecevier / ResultReceiver – send data internal to application.

Register receiver – static (manifest)
Intent intent = new Intent(GET_MESSAGE); // late Banding
sendBroadcast(intent);
Class ReceiverClient extends BrodcastReceiver {
@override Public void onReceive(Context context, Intent intent){
// run on main thread . . . (context can be use to start activity/service…)
}

• Manifest :
<receiver android:name=".ReceiverClient">
<intent-filter>
<action android:name="com.dori.getMessage" />
</intent-filter>
119
</receiver>

Register receiver dynamic (programmatically)

onResume(){
registerReceiver(receiver,intentFilter);
}

onPause(){
unRegisterRecevier(recevier);
}

120

LocalBroadcastManager
• Used to register and send broadcasts of Intents within your process. This is faster and more secure as your
events don't leave your application.
LocalBroadcastManager.getInstance(this).sendBroadcast(new Intent(“WOW”)); - Send
In Activity:
private BroadcastReceiver mMessageReceiver = new BroadcastReceiver() {
@Override public void onReceive(Context context, Intent intent) {
...
}
@Override public void onResume() { //register
LocalBroadcastManager.getInstance(this).registerReceiver(mMessageReceiver, new IntentFilter(“WOW"));
}
@Override protected void onPause() { // Unregister since the activity is not visible
LocalBroadcastManager.getInstance(this).unregisterReceiver(mMessageReceiver);
} 121

Working with Broadcast
– By registering a Broadcast Receiver, application can listen for broadcast Intents that
match specific filter criteria.
– broadcast message can be received by more than one receiver (Receiver)
– Broadcast receiver has 10 sec‟ to do action till application will throw ANR message
(application not responding) unlike activity which has 5 seconds

– By default run on the main thread
– Broadcast Receivers will automatically start application to respond to an incoming
Intent.
•

As of Android 3.1 the Android system will by default exclude
all BroadcastReceiver from receiving intents if the corresponding application has
never been started by the user.

– Unlike a service, a broadcast receiver cant be restarted
123

Long run receiver
Example: If you want a receiver that will listen to incoming SMS and will handle SMS
which comes from specific location:
1.

Acquire a wakelock in the receiver (listen also to BOOT_COMPLETED)

2.

start service from the receiver (in case process will be shut down to clean resources,
service will restart)

3.

Start a separate thread from the service (avoid the 5sec limit of main thread)

4.

The background thread will post a message through a handler back to the service

5.

The background thread will update the service to stop itself either directly or through
a handler

6.

Have the service release the wake lock

124

Broadcast advanced
• Normal broadcasts (sent with Context.sendBroadcast) are completely asynchronous. All receivers of
the broadcast are run in an undefined order, often at the same time.
• Ordered broadcasts (sent with Context.sendOrderedBroadcast) are delivered to one receiver at a time.
As each receiver executes in turn (Q), it can propagate a result to the next receiver, or it can completely
abort the broadcast so that it won't be passed to other receivers. The order receivers run in can be
controlled with the android:priority attribute of the matching intent-filter.

• sendStickyBroadcast (intent) –
– A normal broadcast Intent is not available anymore after is was send and processed by the
system. Perform a sendBroadcast(Intent) that is "sticky," meaning the Intent you are sending stays
around after the broadcast is complete, so that others can quickly retrieve that data through the return
value of registerReceiver(BroadcastReceiver, IntentFilter), by register to sticky event you don‟t need to
wait for next event to be trigger in order to get the data (Battery level)
125

Links
• http://www.compiletimeerror.com/2013/03/android-broadcast-receiver-in-detail.html#.Ukxj44Z9v2B
• http://www.intertech.com/Blog/using-localbroadcastmanager-in-service-to-activity-communications/
• http://www.vogella.com/articles/AndroidBroadcastReceiver/article.html

126

Pending Intent &
Alarm Manager

Pending Intent
• Android allows a component to store an intent for future use by wrapping intent with PendingIntent .
• A PendingIntent is an intent that you give to another application (Notification Manager, Alarm Manager, or
other 3rd party applications), which allows the foreign application to use your application's
permissions to execute a predefined piece of code, on your behalf, at a later time.
• If you give the foreign application an Intent, they will execute the Intent with their own permissions. But if you
give a PendingIntent , that application will execute the contained Intent using your permission.
• To get PendingIntent you will not use C‟tor (Android manage pool of PendingIntent)
– PendingIntent.getActivity(context, requestCode, intent, flags)//start activity
– PendingIntent.getService(context, requestCode, intent, flags) //start service
– PendingIntent.getBroadcast(context, requestCode, intent, flags) // call broadcast receiver
flag indicates what to do if there is an existing pending intent – whether to cancel it, overwrite its extra data..
request code/id is used to distinguish two pending intents when their underlying intents are the same.
For example AlarmManager will invoke the last call in case you will use pending intent with same
128 Id, but if you will use different Id then AM will invoke all calls

Alarm Manager (Scheduler)
• Used to trigger event at specific time or schedule EVEN IF THE APPLICATION IS CLOSED. They are
managed outside of the application scope.
• If the application is running it probably be better to invoke timer tasks with
Timer/Threads/Background services.
• Usage:

• get Alarm Manager instance
• Provide to the Alarm Manager, PendingIntent which will be caught by the receiver
One time: alarmManager.set(AlarmManager.RTC_WAKEUP, firstTime, pendintIntent);
Repeat : am.setRepeating(AlarmManager.RTC_WAKEUP, firstTime, 5*1000, pendintIntent);//every 5 sec

130

Alarm Manager Flags:
–

–

RTC
• fire the intent but not wake the device

–

ELAPSED_REALTIME
• fire the intent based on the amount of time since device was reboot but does not wake the device

–

131

RTC_WAKEUP
• wake the device from sleep in order to fire the intent

ELAPSED_REALTIME_WAKEUP
• wake the device and fire intent after amount of time has passed since device has been reboot

Persistence
• Android provide 3 kinds of persistence:
– Shared Preferences (Properties files)
– Files
– Database

133

Shared Preferences (properties files)
–

Fast & Easy Persistent mechanism
– Support for primitive ,Boolean, string, float, long, and integer
– Can be private to the application or global(shared) to all applications

• Preferences files located at (emulator) : data/data/<package name>/shared_pref/<preferences
name>
SharedPreferences preferences = getSharedPreferences("myPref", MODE_PRIVATE);
preferences = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());
Editor editor = preferences.edit();
editor.putString("mykey", “mayValue”);
editor.commit(); //in activity A
preferences.getInt("mykey", “defaultValue”) // in activity B
134

Shared Preferences – UI (select option from list)
• Android provide built-in UI preferences classes like : CheckBoxPreference ,
EditTextPreference, PreferencesActivity, those object has
onSharedPreferencesChangeListener for ui changes.

135

The „Activity‟ Special Shared Preferences
• Activity.getPreferences(Mode.Private) without specify name – this is used to save
activity preferences which are not shared with other objects in the application.
• Bundle in onCreate(bundle)/ onSaveInstanceState(bundle) ,
onRestoreInstantState(bundle) is a private case of shared preferences that will not be
share among other activities in the same application, this is used to persist UI state in
case OS terminate the activity and restart it like Rotate device.

136

Files
// private file associated with this Context's application package
FileOutputStream fos = openFileOutput(FILE_NAME, Context.MODE_PRIVATE);
FileInputStream fis = openFileInput(FILE_NAME);

• File Management Tools :

–

DeleteFile
– FileList – array with all files name which has been created by the application

137

Database (SqlLite)
• SqlLite is an relational database that comes with android
– stored at /data/data/<package_name>/databases (visible from emulator)
– By default, all databases are private, accessible only by the application that created
them.
– To share a database across applications, use Content Providers
– Android save database version and compare it during app upgrade in order to verify it
DB needs to rebuild.
–

138

GUI tool http://sqliteman.com/ ,
http://cduu.wordpress.com/2011/10/03/sqlitemanager-for-android-eclipse-plugin/

SqlLite:
• sqlLiteOpenHelper object used to manage the logic of create/update DB/Table
This object also provide cache mechanism and
– getWritableDatabase() - create and/or open a database that will be used for reading and
writing.
– getReadableDatabase() - create and/or open a database
• Queries in Android are returned as Cursor objects.
Cursor cursor = query(
table ,// from
columns, //Which columns to return like new String[]{FIRST_COLUMN,SECOND_COLUMN};
selection, // select criteria
selectionArgs, //criteria values
groupby,
having,
140
order);

Working with cursor
• You need to use moveToFirst() because the cursor is positioned before the first row.
• The cursor can move forward and backward.

if (cur.moveToFirst() == false)
//no rows empty cursor
return;
while(cur.moveToNext())
//cursor moved successfully
//access fields
141

Working with cursor
All field-access methods are based on column number, so you must convert the column name
to a column number first :
• You need to know the column names : int column_Index=cur.getColumnIndex(“age”); //2
• You need to know the column types : int age = cursor.getInt(column_Index)
• ContentValues objects are used to insert new rows into tables
ContentValues contentValues = new ContentValues();
contentValues.put("name", person.getName());
contentValues.put("age", person.getAge());
db.insert(DATABASE_TABLE, null, contentValues);

142

//30

Cursor usage
• it‟s strongly recommended that all tables include an auto increment key field called “_id”
which is mandatory for contentProvides which represents the row ID.

143

SQL FTS
http://blog.andresteingress.com/2011/09/30/android-quick-tip-using-sqlite-ftstables/
• If your data is stored in a SQLite database on the device, performing a full-text search
(using FTS3, rather than a LIKE query) can provide a more robust search across text
data and can produce results significantly faster.
• FTS = creating virtual tables which in fact maintain an inverted index for full-text
searches

144

ORM
• http://ormlite.com/sqlite_java_android_orm.shtml

145

ViewBinder
• Use it In case you need to change the display format of the values fetched by cursor (different display
for dateTime)
• Cursor.setViewBinder()

146

NoSql
http://www.couchbase.com/mobile

147

Content Provider
• Content Provider are used to share data among applications without exposing the storage
layer (for example retrieve contact list)
• Access to Content Providers is handled by the ContentResolver (query, insert, update, delete)

• Syntax is REST-like URIs,
– Retrieve a specific book (23)
• content://com.android.book.BookProvider/books/23
– Retrieve all books
• content://com.android.book.BookProvider/books

149

ContentProvider require to Manage the Cursor
• startManagingCursor(cursor) –
– Manage the Cursor lifecycle within your Activities.
• When the activity terminates, all managed cursors will be closed.
• when the activity is paused, it will automatically deactivate the cursor.
• Invoke requery() on the cursor each time the activity returns from a stopped state
• managedQuery
– A wrapper around the ContentResolver's query() + startManagingCursor(cursor)
– performs a query on the main UI thread 
using ContentResolver's query() require to manage the Cursor (startManagingCursor)
150

ContentProvider - queries
• Example:
Uri contacts_uri = Contacts.People.CONTENT_URI; (android built in provider)
string[] projection = new string[] {People._ID,People.NAME,People.NUMBER ;
Cursor managedCursor = getContentResolver (). managedQuery(
contacts_uri, //URI
projection, //Which columns to return.
“id=“, // WHERE clause
new String[] {23} , // where values
Contacts.People.NAME + " ASC"); // Order-by clause.

151

ContentProvider – queries (/23)
• Example:
Uri contacts_uri = Contacts.People.CONTENT_URI; (android built in provider)
Uri myPersonUri = peopleBaseUri.withAppendedId(contacts_uri , 23);
string[] projection = new string[] {People._ID,People.NAME,People.NUMBER ;
Cursor managedCursor = getContentResolver (). managedQuery (
myPersonUri , //URI in this example its already include where people.Id=23
projection, //Which columns to return.
null, // WHERE clause
null, // where values
Contacts.People.NAME + " ASC"); // Order-by clause.
• Demo (Ex8 –must create 2 contacts person before)
152

ContentProvider – add new data
• Adding new entry
ContentValues values = new ContentValues();
values.put("title", "New note");
values.put("note","This is a new note");
ContentResolver contentResolver = activity.getContentResolver();
Uri uri = contentResolver.insert(Notepad.Notes.CONTENT_URI, values);
This call returns a URI pointing to the newly inserted record

153

Create custom Content Provider
–
–

Implement methods: query, insert, update, delete, and getType.

–

Register the provider in the manifest file.

–

154

Extend the abstract class ContentProvider.

Example

CursorLoader (3.0+)
It‟s a loader that queries the ContentResolver and returns a Cursor
From Activity/fragment:
LoaderManager lm = getLoaderManager();
lm.initLoader(LOADER_ID, null, loaderCallback); //create or reuse loader
LoaderCallbacks<Cursor> loaderCallback = new LoaderCallbacks<Cursor>() {
@Override public Loader<Cursor> onCreateLoader(int id , Bundle arg1) {
if(id==LOADER_ID){
return new CursorLoader(context, CONTENT_URI, null, null, null, ContactsContract.Contacts.DISPLAY_NAME + " ASC");
}
}
@Override public void onLoadFinished(Loader<Cursor> loader, final Cursor cursor) {
if(loader.getId()== LOADER_ID){
updateView(cursor); // in main thread
}
@Override public void onLoaderReset(Loader<Cursor> loader) {
// Loader's data is now unavailable Remove any references to the old data by replacing it a null Cursor.
155

}

updateView(null)

Why Use Loader ?
• CursorLoader handle cursor lifetime , instead of to use manageQuery , startManagingCursor
– Requery() will invoke only when underline data has been changed , (activity restart will not
trigger it)
– all cursor operations are done asynchronously, main thread is safe.

• No need to implement Observer , has cursorLoader observer any data changes
• http://www.androiddesignpatterns.com/2012/07/loaders-and-loadermanagerbackground.html
• http://helpmeco.de/2012/3/using-an-android-cursor-loader-with-a-content-provider

156

Loader with without ContentProvider ?
• https://www.grokkingandroid.com/using-loaders-in-android/
• Since Android‟s CursorLoader is only for Cursors returned by content providers we need another
Loader implementation if we want to use SQLite directly.

157

Location-API
(location data)

Location API
V2

Mapping-API
(display location)

Location providers:
•

GPS:
– is most accurate,
– it only works outdoors,
– it quickly consumes battery power,
– doesn't return the location as quickly
as users want.

•

Network Location Provider determines
user location using cell tower and Wi-Fi
signals
– providing location information in a way
that works indoors and outdoors,
– responds faster,
– uses less battery power.
159

Best performance

http://developer.android.com/guide/topics/location/strategies.html
Fuse Location
(12:18)
160

Location API
•

Depending on the device, there may be several technologies (Location Provider) to
determine the location.

•

You cant assume that GPS for example will be available on all devices or that its
already enable when you will use it.

•

Location Provider, can offer different capabilities like power consumption, accuracy, the
ability to determine altitude, speed, distanceBetween()

161

New One API
new location api

LocationClient (context, GooglePlayServicesClient client, …)
onStart()/onStop() you will need to invoke mLocationClient.connect()/disconnect().
ActivityRecognitionClient - detect if the user is currently on foot, in a car, on a bicycle
or still.

162

Getting Location details (old API)
Location location = locationManager.getLastKnownLocation(provider)
• Return the last known location, Location object hold all information from provider like
speed...
•

If the device has not recently updated the current location may be out of date!!!

• To get updates when location has been changed use
locationManager.requestLocationUpdates(provider, 9000,200,locationListener);
best practice to minimize update call by time/distance like in the example : 9 seconds, 200
meters
• To stop location updates:
locationManager.removeUpdates(myLocationListener);
163

Get Provider (old API)
•

LocationProvider.getProvider(providerName) is used to specify which provider you
want like GPS

•

Another option is specify the requirements (criteria) that a provider must meet and let
Android return the best provider to use.
Criteria criteria = new Criteria();
criteria.setAccuracy(Criteria.ACCURACY_COARSE);
criteria.setPowerRequirement(Criteria.POWER_LOW);
criteria.setAltitudeRequired(false);
criteria.setBearingRequired(false);
criteria.setSpeedRequired(false);
criteria.setCostAllowed(true);

String bestProvider = locationManager.getBestProvider(criteria, true);
164

Proximity (old API) – GeoFencing (new API)
•

•

165

application can listen to proximity alert which will fire if the device crosses over that
boundary, both when it moves within the radius and when it moves beyond it
To set proximity you need to provide the following parameters:
– select the center point :longitude and latitude
– radius around that point,
– expiry time-out for the alert.

Projection (Screen to GeoPoint)
Translate between latitude/longitude coordinates (stored as GeoPoints) and x/y screen pixel
coordinates (stored as Points).
When user click on the screen you will probably want to know the geo location coordinates of
the user click
• GoogleMap.OnMapClickListener (onMapClick(LatLng point))
•

Projection proj = mMap.getProjection();
Point startPoint = proj.toScreenLocation(new LatLng(-31.952854, 115.857342));
LatLng myLat= proj.fromScreenLocation(startPoint)

// Android 2.0 code
Projection projection = mapView.getProjection();
projection.toPixels(geoPoint, myPoint); //to screen cords
projection.fromPixels(myPoint.x, myPoint.y); //to GeoPoint
166

Geocoder (Address to GeoPoint)
•
•
•
•

•

Translate between street addresses and longitude/latitude map coordinates
(contextualized using a locale)
Return a list of Address objects. Which contain several possible results, up to a limit you
specify when making the call
Geocoder lookups should be perform in separate thread
The accuracy and granularity of reverse lookups are entirely dependent on the quality of
data in the geocoding database; as such, the quality of the results may vary widely
between different countries and locales.
if no matches are found, null will be returned.

Geocoder geocoder = new Geocoder(getApplicationContext(),Locale.getDefault());
List<Address> addresses = geocoder.getFromLocation(latitude, longitude, number_of_results);

String streetAddress = “160 Riverside Drive, New York, New York”;
167

List<Address> result =geocoder.getFromLocationName(aStreetAddress, number_of_results);

Permission
•

Adding permission to the manifest:

<uses-permission android:name=”android.permission.ACCESS_FINE_LOCATION”/> -

GPS
<uses-permission android:name=”android.permission.ACCESS_COARSE_LOCATION”/> - Network
•

You cant assume that the GPS/WIFI are enable you need to check in code

locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER)
With new API you need to check that GoogleServices are used)

•

In order to open location settings screen

startActivityForResult(new
Intent(android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS), 0);

168

Map API (paint the map, add icons)
https://developers.google.com/maps/documentation/android/
Google Map handles the following operations:
– Connecting to the Google Maps service.
– Downloading and display map tiles.
– Manage controls such zoom.
– Allows to add icons on the map.

What is new in V2 (3D & indoor support)

169

MapFragment (recommended)
•

MapFragment is a subclass of the Android Fragment class, allows you to place a map
in an Android Fragment.

•

MapFragment objects act as containers for the map, and provide access to
the GoogleMap object.

•

SupportMapFragment class (API -12 backward compatibility)

171

MapView
•

MapView is a subclass of the Android View class, allows you to place a map in an
Android View.

•

MapView acts as a container for the Map, exposing core map functionality through
the GoogleMap object.

•

Users of this class must forward all the life cycle methods from the Activity or Fragment
containing this view to the corresponding ones in this class (onCreate()…)

172

Overlay
A Ground overlay - an image that is fixed to a map
A Tile Overlay is a set of images which are displayed on top of the base map
tiles.
These tiles may be transparent, allowing you to add features to existing maps
unlike other overlays, if the map is recreated, tile overlays are not automatically
restored and must be re-added manually.

173

Mapping API (api version1 )
MapView – Map Layout supports several modes: map, street view, satellite, and
traffic
MapActivity - Special activity which handle map activities
MapController is used to control the map, allowing you to set the center location
and zoom levels.
Overlay – used to draw layers via canvas on top the map, The Overlay class itself
cannot be instantiated, so you‟ll have to extend it or use one of the extensions.
MyLocationOverlay is a special overlay that can be used to display the current
position and orientation(Compass) of the device.
ItemizedOverlays provide a convenient way to create Overlay with image/text
handles the drawing, placement, click handling, focus control, and layout
optimization of each OverlayItem marker for you.
174

Debug
log messages:
•

Log.i(“tag”,”message”);

Trace File:
Create log files that give details about an application, such as a call stack and start/stop times
for any running methods.
• Debug.startMethodTracing(“myFile”) - create a trace file mnt/sdcard/myFile.trace (put in
onCreate() and stopMethodTracing , in onStop(), don‟t put in onDestroy())
•

176

Use TraceView from DDMS (or run it as standalone utility) to view the result

TraceView
Execution timeline

Why is something running on the main thread
for that long?

http://www.littleeye.co/
profiler
analysis
177

Function statistics

A call about time zones is taking this long?

StrictMode
Report violations of policies related to threads and virtual machine (memory leak, IO).
most commonly used to catch accidental disk or network access on the application's main thread.
If a policy violation is detected, a stack trace will appear which will show where the application was
when the violation occurred.
03-14 08:56:19.665: D/StrictMode(6309):

StrictMode policy violation; ~duration=8925 ms: android.os.StrictMode$StrictModeNetworkViolation: policy=23 violation=4

03-14 08:56:19.665: D/StrictMode(6309):

at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1105)

03-14 08:56:19.665: D/StrictMode(6309):

at java.net.InetAddress.lookupHostByName(InetAddress.java:391)

03-14 08:56:19.665: D/StrictMode(6309):

at java.net.InetAddress.getAllByNameImpl(InetAddress.java:242)

03-14 08:56:19.665: D/StrictMode(6309):

at java.net.InetAddress.getAllByName(InetAddress.java:220)

03-14 08:56:19.665: D/StrictMode(6309):

at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:137)

03-14 08:56:19.665: D/StrictMode(6309):

at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164)

03-14 08:56:19.665: D/StrictMode(6309):

at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119)

03-14 08:56:19.665: D/StrictMode(6309):

at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360)

03-14 08:56:19.665: D/StrictMode(6309):

at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)

03-14 08:56:19.665: D/StrictMode(6309):


03-14 08:56:19.665: D/StrictMode(6309):


03-14 08:56:19.665: D/StrictMode(6309):

at com.dori.MyAct.getHttpContent(MyAct.java:61)

178

03-14 08:56:19.665: D/StrictMode(6309):

at com.dori.MyAct.onCreate(MyAct.java:38)

Adb debug commands
•

Debug.dumpHprofData -Dump "hprof" data

•

Debug.dumpService -Get a debugging dump of a system service by name

•

Adb shell dumpsys - gives a wealth of information about the applications on the
phone, and the current state of the phone

•

adb bugreport -Prints dumpsys, dumpstate, and logcat.

180

Http Clients:
• HttpURLConnection
• Apache HTTP Client
•
•

DefaultHttpClient - Default implementation of an HTTP client
AndroidHttpClient - Implementation of the Apache DefaultHttpClient that is configured
with reasonable default settings and registered schemes for Android.

Both support HTTPS, streaming uploads and downloads, configurable timeouts,
IPv6 and connection pooling.
• Best practice is to create one instance of HttpClient for the application (in the
application object)
182

Which client is best?
Apache HTTP client has fewer bugs on Eclair and Froyo. It is the best choice for these
releases.
From Gingerbread HttpURLConnection is the best choice.

“New applications should use HttpURLConnection it is where we will be spending
our energy going forward.”

183

Manifest Http Permission
To access the Internet:
android.permission.INTERNET
To check the network state:
android.permission.ACCESS_NETWORK_STATE.

184

HttpURLConnection
HttpURLConnection conn = (HttpURLConnection) newURL(“www.google.com”).openConnection();
InputStream is= conn.getInputStream();

185

Apache Http Client
HttpClient client = new DefaultHttpClient();
--------------------------------------------------------------------------------HttpGet request = new HttpGet();
request.setURI(new URI("http://myWebSite?param=value"));
HttpResponse response = client.execute(request);
--------------------------------------------------------------------------HttpPost request = new HttpPost(http://myWebSite);
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair(“param", "value"));
UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(params );
request.setEntity(formEntity);
HttpResponse response = client.execute(request);
186

Rest:
•

Google-IO – REST App Development GuideLines

•

RestTemplate , examples
RestTemplate restTemplate = new RestTemplate();
Map<String, String> vars = new HashMap<String, String>();
vars.put("hotel", "42");
vars.put("booking", "21");
String result = restTemplate.getForObject("http://example.com/hotels/{hotel}/bookings/{booking}",
String.class, vars);
String url = "https://ajax.googleapis.com/ajax/services/search/web?v=1.0&q={query}";
String result = restTemplate.getForObject(url, String.class, "whatever");

187

restTemplate.getMessageConverters().add(new GsonHttpMessageConverter());
answer[] answers = restTemplate.postForObject(url, requestObject, answer[].class);

Rest Frameworks:
•
•
•

Crest
RestEasy : resteasy-mobile RestEasy
Restlet

Web-Service Clients (Ksoap)

188

Web Server
i-jetty – Install web server on android device

189

WebSocket
http://autobahn.ws/

190

Volley
Easy, Fast Networking for Android

Code Example
•
•
•
•
•
•

Invoke Http calls via Thread Pool not synchronic,
Cache requests (rotate device)
Faster (select http library like Spring – Android),
Remove plumbing code,
Cancel API
Much more…

1- Create a request
2- Add to requestQ
3- The response is in the Main Thread
191

Application Signature
Android applications have to be signed with a digital certificate.
upgrade application can be allowed only if it contain same signature, If you sign the
application with a different signature, Android treats them as two different applications.

Android tests the certificate‟s expiration only at install time. Once application is installed, it
will continue to run even if the certificate expires But update will not be allowed in case
application certificate expires.

193

Application signing involves 3 steps:
•

generate a certificate using the keytool

•

using the jarsigner tool to sign the .apk file with the signature of the generated certificate

•

Use zipAlign to minimize memory resources

194

Application signing steps:
•

Create a folder to hold the keystore, for example c:androidrelease
keytool -genkey -v -keystore "c:androidreleaserelease.keystore" -alias testAlias storepass password -keypass password -keyalg RSA -validity 14000

•

jarsigner tool input parameters are the apk file which needs to be signed and the
certificate.
jarsigner -keystore c:androidreleaserelease.keystore -storepass password keypass password C:android_export_appgeocoder.apk testAlias

(In order to create x.apk file: right-clicking an Android project in Eclipse  selecting
Android Tools  selecting Export Unsigned Application Package)

196

ZipAlign
•

If the application contains uncompressed data like images Android can map this data in
the memory, But the data must be aligned on a 4-byte memory

•

zipalign tool, moves uncompressed data not already on a 4-byte memory boundary to
a 4-byte memory boundary

•
•

197

zipalign –v 4 infile.apk outfile.apk
It is very important that you align after signing, otherwise, signing could cause things to
go back out of alignment.

ProGuard http://proguard.sourceforge.net/index.html
•

Java class file shrinker, optimizer, obfuscator, and preverifier.

•

It detects and removes unused classes, fields, methods, and attributes.

•

It optimizes bytecode and removes unused instructions.

•

It renames the remaining classes, fields, and methods using short meaningless names.

•

Usage can be taken for build.xml of Zxing application
http://code.google.com/p/zxing/source/browse/trunk/android/build.xml

198

uses-permission – During App Installation
<uses-permission android:name="android.permission.INTERNET“/>
<uses-permission android:name="android.permission.READ_PHONE_STATE“/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE“ />
<uses-permission android:name="android.permission.CHANGE_NETWORK_STATE“/>
<uses-permission android:name="android.permission.READ_CONTACTS" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

199

Permission - (permission + permissionClient apps)
Using permission to protect resources
<permission android:protectionLevel="normal“ android:name="com.myPermission“/>
MyAct activity should be launched only by applications which have the “com.myPermission”
permission
<activity android:name=".MyAct“ android:label="@string/app_name"
android:permission="com.myPermission">
</activity>
Add to the client application (permissionClient , will open permission application)
<uses-permission android:name="com.myPermission"></uses-permission>
200

URI permissions
•

Each application run within a separate process, which has a unique and permanent user
ID (assigned at install time),this prevents one application from having direct access to
another‟s data

Partial permission:
• In case you need to provide access finer than all or nothing,for example in case you need
to show incoming emails but not their attachments
• This is where URI permissions come in:
• When invoking another activity and passing a URI, your application can specify that it is
granting permissions to the URI being passed, By grantUriPermission() method and
passing flag:
Intent.FLAG_GRANT_READ_URI_PERMISSION or Intent.FLAG_GRANT_WRITE_URI_PERMISSION

201

Packaging - UserId
•

Each .apk file is uniquely identified by its root package name like “com.dori.test” which
is specified in its manifest file, The package name is tied to the application signature
• Android uses the package name as the name of the process under which to run the
application, By default each package runs in its own process
• User Id: Android allocates a unique user ID for each package process. The id is used
as an ID for the underlying Linux OS
• “shared user ID” allow applications to share data and even run in the same process
Add in manifast: sharedUserId="com.test.mysharedusrid“
After adding it in the manifest you can use createPackageContext() which will return the
context for the other application
• Context targetContext = createPackageContext(“com.dori.test”, flag)
targetContext.getResources();

202

Library Projects (~jar with android context)
•

A library project is an android project which does not create a apk file

•

Maven genarete apkLib , while Gradle generate .AAR (android archive)

204

Supported Sensors
•
•
•
•
•
•
•
•
•
•
•

206

Temperature
Accelerometer
Gravity
Gyroscope
Rotation
Magnetic Field
Atmospheric Pressure
Humidity
Proximity – distance (cm) between device and target object
Light
Example Accelerometer

Links
UI generator tool
IDE UI tips

Android UI Tools
Android Design Tips
Android UI Patterns
http://www.androidpatterns.com/

208

Android special Views
Surface View
can be drawn from background thread but this option cost in memory usage.
use with caution (when you need rapid updating the UI view (animation)).
ViewStub
is an invisible, zero-sized View that can be used to lazily inflate layout resources at
runtime, when the viewStub is visible ViewStub then replaces itself in its parent with
the inflated View or Views
To Improve performance use ViewStub (lazy)

209

Theme
<activity android:theme="@android:style/Theme.Translucent">  built in Theme (background to be transparent)

Holo Light

210

Holo Dark

Holo Light with dark action bars

Use style (~ css)
<TextView

style="@style/CodeFont"
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textColor="#00FF00"
android:typeface="monospace"
android:text="@string/hello" />

211

android:text="@string/hello" />

<?xml version="1.0" encoding="utf-8"?>
<resources>
<style name="CodeFont"
parent="@android:style/TextAppearance.Medium">
<item name="android:layout_width">fill_parent</item>
<item name="android:layout_height">wrap_content</item>
<item name="android:textColor">#00FF00</item>
<item name="android:typeface">monospace</item>
</style>
</resources>

ActionBar (new navigation)
Navigating up Example

214

What is DP ?
DP purpose is to remain the “same” UI element size from the user's point of view,
regardless the screen resolution.

android resolution

216

Scale UI Elements
•

When you define height/width UI element like Button its recommended not to use specific
dimensions , use match_parent / wrap_content,
• If you cant , Use sp or dp:
• Dp (density independent pixels) – use this for non text elements
• Sp (scale) – like dp but it is also scaled according to the user's font size preference.
use this unit for font sizes, so they will be adjusted for both the screen density and
user's preference.
• Px (not recommended !!!) px = dp * (dpi / 160).
scaleing is according to the space available and screen density.
<support-screens android:smallScreens=“false” android:normalScreens=“true”
android:requiersSmallestWidthDp=480 />
217

Support multiple screens
Android divides the range of actual screen sizes and densities into:
• Categories sizes: small, normal, large, and xlarge
• Categories densities: LDPI (low), MDPI (medium), HDPI (high), and XHDPI (extra high)
To optimize application's UI its recommended to designing layouts/bitmap images per screen
size.

218

9Patch
• To Scale PNG images use NinePatch-PNG :
specify which parts of the images cab be stretched, and provide images per
resolution
draw9Patch

219

Gravity:
•

android:layout_gravity is the Outside gravity of the view (relative to the parent)

•

android:gravity is the Inside gravity of that View (its content alignment)

Combination is supported: android:layout_gravity="center_horizontal|bottom"

220

android:layout_weight (like % in css)
for table layout similar functionality
is achieved via
android:stretchColumns
android:shrinkColumns
android:collapseColumns

221

Usability Tips
• Login should be simple (or limited)
• Minimum navigate
• Your mobile is personalize , your app should be too

222

Admin App
http://developer.android.com/guide/topics/admin/device-admin.html

223

Adapter
•
•
•
•

Adapter are used to bind Data to Views.
They are responsible for creating the child views
Any data modification will cause the view to be updated
You need to create just one row layout that will be repeat for all rows

•
•

Support Functionality like scrolling, click on row.
Basic adapters are :
•
•

225

ArrayAdapter
SimpleCursorAdapter

Adapters
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this,R.array.cars, android.R.layout.simple_spinner_item);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,new string[]{“A",“B",”C”});

“notifyDataSetChanged()” needs to be called after adding/deleting items to the adapter in order
to update the view with the underline datasource changes.
In case you are using cursorAdapter there is no need to invoke it.

226

Custom Adapters (ViewHolder pattern)
In case you want to manage the display of child views:
Create custom adapter by extending BaseAdapter
ViewHolder Pattern improve performance by using cache as well as reusing the View
Object, minimum calls to:
•
•

LayoutInflater.from(context).inflate(R.layout.row, null);
findViewById()

ViewHolder Pattern
adapters

227

How we can improve performance ?
•

Save the images that you already download in a SoftReference hashmap which
allows to save data, if OS need to release memory it will delete the hashmap

•

Parallel loading images to screen

•

Use images thumbnails

•

Use volley Image loader

•

Use ViewHolder pattern

http://blog.dutchworks.nl/2009/09/17/exploring-the-world-of-android-part-2/

228

Toast
• Show message on top application
Toast.makeText(this,“myText”, Toast.LENGTH_LONG).show();
•

230

Create custom toast:
Toast toast = new Toast(getApplicationContext());
toast.setGravity(Gravity.CENTER_VERTICAL, 0, 0);
toast.setDuration(Toast.LENGTH_LONG);
toast.setView(layout); // some layout
toast.show();

Notification
•

•
•
•

Notifications let you notify users without interrupting their current Activities. it‟s a great way
for getting a user‟s attention from within a Service or Broadcast Receiver.
From notification you can invoke activities.
Notification can have extra like sound, vibration, light
RemoteViews (will be explained later) can be used to create custom notification view

232

Widget –
•

widgets are views which display on a home page and can be update frequently
(timer), you can add more than one widget from the same type on the screen (usually with
different settings).

•

Widget minimum time to update is 1H.

•

RemoteView - A class that describes a view hierarchy that can be displayed in another
process. The hierarchy is inflated from a layout resource file, and this class provides some
basic operations for modifying the content of the inflated hierarchy.

•

Widgets use RemoteViews to create there user interface. A RemoteView can be
executed by another process with the same permissions as the original application. This
way the Widget runs with the permissions of its defining application, meaning you can‟t
work on the view directly.

234

Create Widget
Code Example
•

Declare widget in manifest

•

Adding the AppWidgetProviderInfo Metadata (res/xml/)

•

Create widget layouts (View , configure)

•

Extends AppWidgetProvider
This class is responsible to paint the RemoteViews according to the widget instance ID

•

Create Configuration Activity
Instance parameters needs to be persistence

235

What's new
•

Since Android 4.2, it is possible to launch Home Screen application widgets on the
Lock Screen of an Android device.

•

<appwidget-provider xmlns:android="http://schemas.android.com/apk/res/android" android:widgetCategory="keyguard|home_screen" ... > ...
</appwidget-provider>

236

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