Introduction to Volley

Volley is an open-source library written by Google (Android team), released during Google I/O 2013.

Transcript

1. Introduction to Volley
   Paresh Mayani
   

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2. Paresh Mayani
   Sr. Software Engineer @ InfoStretch, India
   Manager, GDG Ahmedabad
   

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3. Writing
   Http code
   every
   time?
   {Less code}
   {Less Mistakes}
   {Faster Development}
   

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4. Volley
   Simultaneous firing of a number of missiles
   

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5. Volley library
   o An open-source library written by Google (Android team)
   o Volley isn’t an image loading library - it’s an asynchronous
   networking library
   o Introduced by Ficus Kirkpatrick at Google I/O 2013
   o It’s not yet added to Android API
   

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6. Advantages
   o Standalone library
   o A high level API to make asynchronous RESTful HTTP requests
   o Schedules all your HTTP requests running them parallel in
   background threads and manages those threads.
   o Good asynchronous performance
   o Provides powerful cancellation request API.
   o Comes with inbuilt JSON parsing the response.
   o Handles memory errors well
   o Retry policy for timeout, certain ERROR codes as Internal
   Server error.
   

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7. Disadvantages
   o It’s not well documented
   o No active contributors
   o Advanced HTTP features need custom code
   

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8. Get Volley
   $ git clone https://android.googlesource.com/platform/frameworks/volley
   $ cd volley
   $ android update project -p .
   $ ant jar
   

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9. Let’s use Volley
   Step 1: Create a RequestQueue Instance
   Step 2: Create a JSONObjectRequest with response and error
   listener.
   Step 3: Add your request into the RequestQueue.
   

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10. Step 1
    Create a RequestQueue Instance
    RequestQueue queue = Volley.newRequestQueue(this);
    

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11. Step 2
    To make asynchronous HTTP requests, there are 3 utility classes
    available:
    JsonObjectRequest - To send and receive JSON Object from the
    Server
    JsonArrayRequest - To receive JSON Array from the Server
    StringRequest - To retrieve response body as String (ideally if
    you intend to parse the response by yourself)
    

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12. Step 2
    Create a JSONObjectRequest with response and error listener.
    JsonObjectRequest jsObjRequest = new JsonObjectRequest(Request.Method.GET, url, null,
    new Response.Listener() {
    @Override
    public void onResponse(JSONObject response) {
    // TODO Auto-generated method stub
    }
    }, new Response.ErrorListener() {
    @Override
    public void onErrorResponse(VolleyError error) {
    // TODO Auto-generated method stub
    }
    });
    

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13. Step 3
    Add your request into the RequestQueue
    queue.add(jsObjRequest);
    

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14. Image loading using Volley
    Step 1: Get NetworkImageView in XML layout
    Step 2: Create ImageLoader object
    Step 3: Load Image using setImageUrl(url, imageLoader)
    

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15. Image loading using Volley
    android:id="@+id/imgDemo"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:scaleType="centerCrop"/>
    ImageLoader.ImageCache imageCache = new BitmapLruCache();
    ImageLoader imageLoader = new ImageLoader(Volley.newRequestQueue(context),
    imageCache);
    NetworkImageView imgDemo = (NetworkImageView) findViewById(R.id.imgDemo);
    imgDemo.setImageUrl(url, imageLoader);
    imgDemo.setDefaultImageResId(..);
    imgDemo.setErrorImageResId(..);
    

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16. References/links
    o https://android.googlesource.com/platform/frameworks/volley/
    o https://developers.google.com/events/io/sessions/325304728
    

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17. Thank You
    +PareshMayani @pareshmayani
    TechnoTalkative.com
    

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