android-social-app-sample/MyVolleySingleton.java

public class MyVolleySingleton {
    private static MyVolleySingleton mInstance;
    private RequestQueue mRequestQueue;
    private ImageLoader mImageLoader;
    private static Context mCtx;
    private static HttpStack httpStack;
    private MyVolleySingleton(Context context) {
        mCtx = context;
        httpStack=new OkHttpStack(mCtx);
        mRequestQueue = getRequestQueue();
        mImageLoader = new ImageLoader(mRequestQueue,
                new ImageLoader.ImageCache() {
                    private final LruCache<String, Bitmap>
                            cache = new LruCache<String, Bitmap>(20);
                    @Override
                    public Bitmap getBitmap(String url) {
                        return cache.get(url);
                    }
                    @Override
                    public void putBitmap(String url, Bitmap bitmap) {
                        cache.put(url, bitmap);
                    }
                });
    }

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

    public RequestQueue getRequestQueue() {
        if (mRequestQueue == null) {
            // getApplicationContext() is key, it keeps you from leaking the
            // Activity or BroadcastReceiver if someone passes one in.
            mRequestQueue = Volley.newRequestQueue(mCtx.getApplicationContext(),httpStack);
        }
        return mRequestQueue;
    }

    public <T> void addToRequestQueue(Request<T> req) {
        getRequestQueue().add(req);
    }

    public ImageLoader getImageLoader() {
        return mImageLoader;
    }

}