PPT on Volley in Android

1. Volley: Easy, Fast
Networking for Android
Prepared by: Himanshu Saini

2. 1. Introduction To Volley
1. Volley is an HTTP library that makes networking for Android
apps easier and most importantly, faster.
2. Volley is developed by Google & introduced during Google
I/O 2013.
3. Volley is available through the AOSP or GitHub.

3.  Using Volley In Your Project
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
compile 'com.android.support:appcompat-
v7:24.0.0'
compile 'com.android.volley:volley:1.0.0'
}

4. 2. Benefits of Volley
 Automatic scheduling of network requests.
 Multiple concurrent network connections.
 Support for request prioritization.
 Cancellation request API. You can cancel a single request, or
you can set blocks or scopes of requests to cancel.
 Ease of customization, for example, for retry and backoff.
 Strong ordering that makes it easy to correctly populate your UI
with data fetched asynchronously from the network.
 Debugging and tracing tools.

5. Comparison Between
AsyncTask
And
Volley

6. AsyncTask

7. Worker Thread
Main Thread
doInBackground()
Http Request
Http Response
 AsyncTask In Android

8. Worker Thread
Main Thread
doInBackground()
Http Request
Http Response
 AsyncTask In Android

9. Volley

10. Main
Thread
Cache Thread
Cache
Dispatcher
Network Thread
Request
Cash Miss
Request
Http Request
Http Response
Response
Response
Cache MemoryResponse
Response

11. Main
Thread
Cache Thread
Cache
Dispatcher
Network Thread
Request
Cash Hit
Cache Memory
Response
Request
Response

12. 2. Sending a Simple Request
 Add the Internet permission
 Use newRequestQueue
 Send a RequestQueue
 Cancel a Request

13. 2.1 Add the Internet Permission
 Add android.permission.INTERNET permission to app's
manifest
<uses-permission android:name="android.permission.INTERNET/>

14. 2.2 Use newRequestQueue
 Volley provides a convenience method
Volley.newRequestQueue that sets up a RequestQueue for
you, using default values, and starts the queue.
// Instantiate the RequestQueue.
RequestQueue queue = Volley.newRequestQueue(this);

15. 2.3 Send a Request
 To send a request, you simply construct one and add it to
the RequestQueue object with add(StringRequest Object).
// Add the request to the RequestQueue.
queue.add(stringRequest);

16. Processing Send a Request

17. Example of RequestQueue and
Send Request

18. 2.4 Cancel a Request
 To cancel a request, call cancelAll()on your Request object.
 We can call cancel a request in onStop() method of An
activtiy
mRequestQueue.cancelAll(Object Tag);
@Override
protected void onStop () {
super.onStop();
if (mRequestQueue != null) {
mRequestQueue.cancelAll(TAG);
}
}

19. Example
 Define your tag and add it to your requests.

20. Example (Contd.)
 In your activity's onStop() method, cancel all requests that
have this tag.

21. 3. Making a Standard Request
 Introduction to Standard Request
 Request an Image
 Use ImageRequest
 Use ImageLoader and NetworkImageView
 Request JSON

22. 3.1 Introduction to Standard
Request
 StringRequest: Specify a URL and receive a raw string in
response.
 ImageRequest: Specify a URL and receive an image in
response.
 JsonObjectRequest and JsonArrayRequest (both
subclasses of JsonRequest): Specify a URL and get a
JSON object or array (respectively) in response.

23. 3.2 Request an Image
 Volley offers the following classes for requesting images.
These classes layer on top of each other to offer different
levels of support for processing images:
 ImageRequest—a canned request for getting an image at a
given URL and calling back with a decoded bitmap. It also
provides convenience features like specifying a size to resize
to.
 ImageLoader—a helper class that handles loading and
caching images from remote URLs. ImageLoader is a an
orchestrator for large numbers of ImageRequests, for example
when putting multiple thumbnails in a ListView.
 NetworkImageView—builds on ImageLoader and effectively
replaces ImageView for situations where your image is being
fetched over the network via URL. NetworkImageView also
manages canceling pending requests if the view is detached
from the hierarchy.

24. 3.3 Use ImageRequest
 Create Singleton Class
 MainActivity.java
 Main_activity.xml

25. 3.3.1 Create Singleton Class

26. 3.3.1 Create Singleton Class
(Contd.)

27. 3.3.2 main_activity.xml

28. 3.3.3 MainActivity.java

29. Output

30. 4. Using Request JSON
 Volley provides the following classes for JSON requests:
 JsonArrayRequest—A request for retrieving a JSONArray
response body at a given URL.
 JsonObjectRequest—A request for retrieving a JSONObject
response body at a given URL, allowing for an optional
JSONObject to be passed in as part of the request body.
Note: Both classes are based on the common base class
JsonRequest.

31. JSON Request
JsonObjectRequest request JsonObjectRequest(RequestMethod,
URL, null, new ResponseListener(), new ErrorListener());
Parameters passed into the constructor:
RequestMethod: (GET, POST, PUT, DELETE, etc.)
URL: String of the URL of the required object
JSONObject: An optional object posted with the request, null if there is no
object posted
ResponseListener: Response Listener, whose callback method will contain
the response
ErrorListener: A Response.ErrorListener whose callback method will
contain any problem with the request.

32. Example: Request JSON
 Create A New Class (MySingleton)
 MainActivity.java Class
 main_activity.xml Class

33. Creating a New Class

34. MainActivity.java

35. THANK YOU