Android Framework and application building blocks

1. Android
Framework and Application
Overview
By: Ashish Agrawal
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2. Agenda
 Mobile Application Development (MAD)
 Introduction to Android platform
 Platform architecture
 Application building blocks
 Lets Debug
 Development tools.
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3. Introduction to Android
 Open software platform for mobile development
 A complete stack – OS, Middleware, Applications
 Powered by Linux operating system
 Fast application development in Java
 Open source under the Apache 2 license
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4. Android Overview 19/12/12 4

5. Application Framework
• API interface
• Activity manager – manages application
life cycle.
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6. Applications
• Built in and user apps
• Can replace built in apps
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7. Application Lifecycle
 Application run in their own processes (VM, PID)
 Processes are started and stopped as needed to run
an application's components
 Processes may be killed to reclaim resources
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8. Application Building Blocks
 Activity
 Fragments
 Intents
 Service (Working in the background)
 Content Providers
 Broadcast receivers
 Action bar
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9. Activities
 Typically correspond to one UI screen
 Run in the process of the .APK which installed them
 But, they can:
 Be faceless
 Be in a floating window
 Return a value
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10. Android Overview 19/12/12
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11. Fragments
Fragment represents a behavior or a portion of user interface in an Activity.
You can combine multiple fragments in a single activity to build a multi-pane
UI and reuse a fragment in multiple activities.
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12. Fragments
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13. Intents
 An intent is an abstract description of an operation to be performed.
 Launch an activity
 Explicit
Ex: Intent intent = new Intent(MyActivity.this, MyOtherActivity.class)
 Implicit : Android selects the best
Ex: Intent intent = new Intent(Intent.ACTION_DIAL, Uri.parse(“tel:
555-2368”));
 startActivity()
 Extra parameter Ex: intent.putExtra(name, property);
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14. Intent Filter
 Register Activities, Services, and Broadcast Receivers as
being capable of performing an action on a particular
kind of data.
 Components that respond to broadcast ‘Intents’
 Way to respond to external notification or alarms
 Apps can invent and broadcast their own Intent
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15. Services
 Faceless components that run in the background
 No GUI, higher priority than inactive Activities
 Usage:  responding to events, polling for data, updating
Content Providers.  However, all in the main thread
 E.g. music player, network download etc…
Intent service = new Intent(context,
WordService.class);
context.startService(service);
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16. Using the Service
Start the service
Intent serviceIntent = new Intent();
serviceIntent.setAction
("com.wissen.testApp.service.MY_SERVICE");
startService(serviceIntent);
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17. Bind the service
ServiceConnection conn = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName
name, IBinder service) {
}
@Override
public void
onServiceDisconnected(ComponentName arg0) {
}
}
bindService(new
Intent("com.testApp.service.MY_SERVICE"), conn,
Context.BIND_AUTO_CREATE);
}
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18. Async Task
Asycn task enables easy and proper use of UI
thread. This class allows to perform background
operations and publish results on the main thread.
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19. Async Task (Example)
private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> {
protected Long doInBackground(URL... urls) {
int count = urls.length;
long totalSize = 0;
for (int i = 0; i < count; i++) {
totalSize += Downloader.downloadFile(urls[i]);
publishProgress((int) ((i / (float) count) * 100));
}
return totalSize;
}
protected void onProgressUpdate(Integer... progress) {
setProgressPercent(progress[0]);
}
protected void onPostExecute(Long result) {
showDialog("Downloaded " + result + " bytes");
}
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}
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20. ContentProviders
 Enables sharing of data across applications
 E.g. address book, photo gallery
 Provides uniform APIs for:
 querying
 delete, update and insert.
 Content is represented by URI and MIME type
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21. Example
private void displayRecords() {
String columns[] = new String[] { People.NAME,
People.NUMBER };
Uri mContacts = People.CONTENT_URI;
Cursor cur = managedQuery(mContacts, columns, null, null,
null );
if (cur.moveToFirst()) {
String name = null;
String phoneNo = null;
do {
name = cur.getString(cur.getColumnIndex(People.NAME));
phoneNo =
cur.getString(cur.getColumnIndex(People.NUMBER));
} while (cur.moveToNext());
}
}
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22. Broadcast Receivers
 A broadcast receiver is a class which extends
BroadcastReceiver and which is registered as a receiver in an
Android Application via the AndroidManifest.xml file(or via
code).
 <receiver android:name="MyPhoneReceiver">
<intent-filter>
<action
android:name="android.intent.action.PHONE_STATE">
</action>
</intent-filter>
</receiver>
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23. Broadcast Receivers
 public class MyBroadcastReceiver extends BroadcastReceiver
{
@Override
public void onReceive(Context context, Intent intent) {
Toast.makeText(context,
”BR.”,Toast.LENGTH_LONG).show();
}
}
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24. ActionBar
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25. ActionBar
 Home Icon area: The icon on the top left-hand side of the action
bar is sometimes called the “Home” icon.
 Title area: The Title area displays the title for the action bar.
 Tabs area: The Tabs area is where the action bar paints the list
of tabs specified. The content of this area is variable.
 Action Icon area: Following the Tabs area, the Action Icon area
shows some of the option menu items as icons.
 Menu Icon area: The last area is the Menu area. It is a single
standard menu icon.
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26. Debugging
•Reading and Writing Logs
Log.d("MyActivity”, position);
•adb logcat
• Toast :
Toast toast = Toast.makeText(context, text, duration);
toast.show();
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27. Debugging Cont.
•Hierarchy Viewer
•Connect your device or launch an emulator.
•If you have not done so already, install the application
you want to work with.
•Run the application, and ensure that its UI is visible.
•From a terminal, launch hierarchyviewer
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28. Debugging Cont.
adb shell dumpsys activity
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29. Debugging Cont.
Profiling for memory
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30. Development Tools
Eclipse
developer.android.com
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31. Thank You.
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