ANDROID HTTP CLIENT & IMAGE LOADER

VOLLEY

Why volley?

Simple
Powerful
Extendable
Build-in memory cache
Build-in disk cache

how to use it?

Step 1 - create request queue

RequestQueue requestQueue =    Volley.newRequestQueue(context.getApplicationContext());

Step 2 - create request

 StringRequest request = new StringRequest(
                Request.Method.GET,
                url,
                listener,
                errorListener);

Step 3 - create listeners

 Response.Listener<String> listener = new Response.Listener<String>() {
    @Override
    public void onResponse(String response) {
        L.d("Success Response: " + response.toString());
    }
};

Response.ErrorListener errorListener = new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
            if (error.networkResponse != null) {
                L.d("Error Response code: " + 
                        error.networkResponse.statusCode);
            }

        }
    };

step 4 - add request to queue

requestQueue.add(request);

Request methods

Request.Method.GET
Request.Method.POST
Request.Method.PUT
Request.Method.DELETE

Request types

Every request listener returns appropriate type

String / JSON Object / JSON Array / Bitmap

or you can create your own..

 public class CookieRequest extends StringRequest {

 private String mCookieValue;

    public CookieRequest(String url, String cookieValue,
            Response.Listener<String> listener,
            Response.ErrorListener errorListener) {
        super(Method.GET, url, listener, errorListener);
        mCookieValue = cookieValue;
    }

    @Override
    public Map<String, String> getHeaders() throws AuthFailureError {
        Map<String, String> map = new HashMap<String, String>();
        map.put("Cookie", mCookieValue);
        return map;
    }

how to pass post request parameters?

@Override getParams() method

StringRequest request = new StringRequest(
        Request.Method.POST,
        url,
        listener,
        errorListener) {
    @Override
    protected Map<String, String> getParams() throws AuthFailureError {

        Map<String, String> map = new HashMap<String, String>();
        map.put("name", "Jon Doe");
        map.put("age", "21");

        return map;
    }
};

how to set request retry policy?

 StringRequest request = new StringRequest(
        Request.Method.GET,
        url,
        listener,
        errorListener);

 request.setRetryPolicy(
        new DefaultRetryPolicy(
                DefaultRetryPolicy.DEFAULT_TIMEOUT_MS, // 2500
                DefaultRetryPolicy.DEFAULT_MAX_RETRIES, // 1
                DefaultRetryPolicy.DEFAULT_BACKOFF_MULT)); //1f

HTTP Basic Auth

StringRequest request = new StringRequest(
        Request.Method.GET,
        url,
        listener,
        errorListener) {

    @Override
    public Map<String, String> getHeaders() throws AuthFailureError {
        return createBasicAuthHeader("user", "passwd");
    }
};

Map<String, String>
    createBasicAuthHeader(String username, String password) {
    Map<String, String> headerMap = new HashMap<String, String>();

    String credentials = username + ":" + password;
    String base64EncodedCredentials =
            Base64.encodeToString(credentials.getBytes(), Base64.NO_WRAP);
    headerMap.put("Authorization", "Basic " + base64EncodedCredentials);

    return headerMap;
}

how to cancel request

 StringRequest request1 = new StringRequest(...);

 request1.setTag("weather-screen");

 StringRequest request2 = new StringRequest(...);

 request2.setTag("weather-screen");

 requestQueue.add(request1);

 requestQueue.add(request2);

to cancel request you just need to remember

request tag

 requestQueue.cancelAll("weather-screen");

i need to instantiate request queue in each

Service or Activity?

no

i need to create singleton wrapper?

yes

Why ?

Request Queue object creation is quite expensive
You will be able to access and cancel all your requests
You will be able to access and clear your cache

example

Request Proxy

wrapper for RequestQueue
holds list of all application requests

Request Manager

singleton which hold RequestProxy

request proxy

 public class RequestProxy {

 private RequestQueue mRequestQueue;

 // package access constructor
 RequestProxy(Context context) {
    mRequestQueue =
            Volley.newRequestQueue(context.getApplicationContext());
 }

 public void login() {
    // login request
 }

 public void weather() {
    // weather request
 }

Request Manager

part 1

public class RequestManager {

private static RequestManager instance;
private RequestProxy mRequestProxy;

private RequestManager(Context context) {
    mRequestProxy = new RequestProxy(context);
}

public RequestProxy doRequest() {
    return mRequestProxy;
}

.. init methods see part 2

REQUEST MANAGER

PART 2

public static synchronized RequestManager getInstance(Context context) {
    if (instance == null) {
        instance = new RequestManager(context);
    }
    return instance;
}

public static synchronized RequestManager getInstance() {
    if (instance == null) {
        throw new IllegalStateException
                (RequestManager.class.getSimpleName() +
                " is not initialized, call getInstance(..) method first.");
    }
    return instance;
}

usage sample

initialize request manager in application class

public class MyApplication extends Application {

    @Override
    public void onCreate() {
        super.onCreate();

        // RequestManager initialization
        RequestManager.getInstance(getApplicationContext());
    }
}

start requests

RequestManager.getInstance().doRequest().login(..);
RequestManager.getInstance().doRequest().weather(..);

image loader

you need to load image?

we have view for this!

 <com.android.volley.toolbox.NetworkImageView
        android:id="@+id/imgAvatar"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:scaleType="centerCrop"/>

just set up url and image loader

NetworkImageView imgAvatar =
        (NetworkImageView) findViewById(R.id.imgAvatar);
imageView.setImageUrl(url, imageLoader);
imageView.setDefaultImageResId(..);
imageView.setErrorImageResId(..);

wait what?.. image loader?

YES

to create image loader we need 2 things:

RequestQueue
ImageCache

ImageLoader imageLoader = 
        new ImageLoader(Volley.newRequestQueue(context), imageCache);

memory cache part 1

public class BitmapLruCache
        extends LruCache<String, Bitmap>
        implements ImageLoader.ImageCache {

public BitmapLruCache() {
    this(getDefaultLruCacheSize());
}

public BitmapLruCache(int sizeInKiloBytes) {
    super(sizeInKiloBytes);
}

 .. more methods see part 2

public static int getDefaultLruCacheSize() {
    final int maxMemory =
            (int) (Runtime.getRuntime().maxMemory() / 1024);
    final int cacheSize = maxMemory / 8;

    return cacheSize;
}

MEMORY CACHE PART 2

@Override
protected int sizeOf(String key, Bitmap value) {
    return value.getRowBytes() * value.getHeight() / 1024;
}

@Override
public Bitmap getBitmap(String url) {
    return get(url);
}

@Override
public void putBitmap(String url, Bitmap bitmap) {
    put(url, bitmap);
}

put it all together

ImageLoader.ImageCache imageCache = new BitmapLruCache();ImageLoader imageLoader =
        new ImageLoader(Volley.newRequestQueue(context), imageCache);

<com.android.volley.toolbox.NetworkImageView
    android:id="@+id/imgAvatar"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:scaleType="centerCrop"/>

NetworkImageView imgAvatar =
        (NetworkImageView) findViewById(R.id.imgAvatar);
imageView.setImageUrl(url, imageLoader);

Are we ready ?

NO

why ?

we need disk cache

DIG IT

Volley.newRequestQueue(context)

more..

// Inside newRequestQueue methodFile cacheDir = new File(context.getCacheDir(), DEFAULT_CACHE_DIR);

Even more..

Method description: getCacheDir()You should always have a reasonable maximum, such as 1 MB, for the amount of space you consume with cache files, and prune those files when exceeding that space.

is 1 mb

reasonable enough

for

image loader ?

we need to use external cache directory

to cache images

and replace

 Volley.newRequestQueue(context)

with our own implementation

configure request queue part 1

// Default maximum disk usage in bytes.
private static final int DEFAULT_DISK_USAGE_BYTES = 25 * 1024 * 1024;// Default cache folder name
private static final String DEFAULT_CACHE_DIR = "photos";

 private static RequestQueue newRequestQueue(Context context) {

// define cache folderFile rootCache = context.getExternalCacheDir();
if (rootCache == null) {
    L.w("Can't find External Cache Dir, "
            + "switching to application specific cache directory");
    rootCache = context.getCacheDir();
}File cacheDir = new File(rootCache, DEFAULT_CACHE_DIR);
cacheDir.mkdirs();

 .. more lines of code see part 2

CONFIGURE REQUEST QUEUE PART 2

HttpStack stack = new HurlStack();
Network network = new BasicNetwork(stack);

DiskBasedCache diskBasedCache = 
        new DiskBasedCache(cacheDir, DEFAULT_DISK_USAGE_BYTES);
RequestQueue queue = new RequestQueue(diskBasedCache, network);
queue.start();

 return queue;
}

PUT IT ALL TOGETHER... again

ImageLoader.ImageCache imageCache = new BitmapLruCache();
ImageLoader imageLoader =
        new ImageLoader(newRequestQueue(context), imageCache);

<com.android.volley.toolbox.NetworkImageView
        android:id="@+id/imgAvatar"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:scaleType="centerCrop"/>

NetworkImageView imgAvatar =
        (NetworkImageView) findViewById(R.id.imgAvatar);
imageView.setImageUrl(url, imageLoader);

now it should work..

i don't want view, i want bitmap!

don't panic, use image request..

new ImageRequest(
        url,
        listener,
        maxWidth,
        maxHeight,
        decodeConfig,
        errorListener);

 Response.Listener<Bitmap> listener = new Response.Listener<Bitmap>() {
    @Override
    public void onResponse(Bitmap bitmap) {
        // use your bitmap
    }
};

you should know

Volley decides whether to cache response or not

based only on headers "Cache-Control" and "Expires"

Override parseNetworkResponse method and

implement your own parseCacheHeaders method.

@Override
protected Response<String> parseNetworkResponse(NetworkResponse response) {
    try {
        String result = new String(
                response.data, 
                HttpHeaderParser.parseCharset(response.headers));
        return Response.success(result,
                HttpHeaderParser.parseCacheHeaders(response));
    } catch (UnsupportedEncodingException e) {
        return Response.error(new ParseError(e));
    }
}