An OkHttp3Stack for Volley library to boost the performance of Volley itself

OkHttp3Stack.java

import com.android.volley.AuthFailureError;
import com.android.volley.Request;
import com.android.volley.toolbox.HttpStack;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.ProtocolVersion;
import org.apache.http.StatusLine;
import org.apache.http.entity.BasicHttpEntity;
import org.apache.http.message.BasicHeader;
import org.apache.http.message.BasicHttpResponse;
import org.apache.http.message.BasicStatusLine;

import java.io.IOException;
import java.util.Map;

import okhttp3.Call;
import okhttp3.Headers;
import okhttp3.MediaType;
import okhttp3.OkHttpClient;
import okhttp3.Protocol;
import okhttp3.RequestBody;
import okhttp3.Response;
import okhttp3.ResponseBody;

/**
 * OkHttp backed {@link com.android.volley.toolbox.HttpStack HttpStack} that does not
 * use okhttp-urlconnection
 */
@SuppressWarnings("deprecation")
public class OkHttp3Stack implements HttpStack {

    private static OkHttpClient sOkHttpClient;

    public OkHttp3Stack() {
        if (sOkHttpClient == null) {
            sOkHttpClient = OkHttpSingleton.getInstance().getOkHttpClient();
        }
    }

    @Override
    public HttpResponse performRequest(com.android.volley.Request<?> request, Map<String, String> additionalHeaders)
            throws IOException, AuthFailureError {
        okhttp3.Request.Builder okHttpRequestBuilder = new okhttp3.Request.Builder().url(request.getUrl());

        if (request.getTag() != null) {
            okHttpRequestBuilder.tag(request.getTag());
        }

        Map<String, String> headers = request.getHeaders();
        for (final String name : headers.keySet()) {
            okHttpRequestBuilder.addHeader(name, headers.get(name));
        }
        for (final String name : additionalHeaders.keySet()) {
            okHttpRequestBuilder.addHeader(name, additionalHeaders.get(name));
        }

        setConnectionParametersForRequest(okHttpRequestBuilder, request);

        if (sOkHttpClient == null) {
            sOkHttpClient = OkHttpSingleton.getInstance().getOkHttpClient();
        }

        okhttp3.Request okHttpRequest = okHttpRequestBuilder.build();
        Call okHttpCall = sOkHttpClient.newCall(okHttpRequest);
        Response okHttpResponse = okHttpCall.execute();

        StatusLine responseStatus = new BasicStatusLine(parseProtocol(okHttpResponse.protocol()), okHttpResponse.code(), okHttpResponse.message());
        BasicHttpResponse response = new BasicHttpResponse(responseStatus);
        response.setEntity(entityFromOkHttpResponse(okHttpResponse));

        Headers responseHeaders = okHttpResponse.headers();
        for (int i = 0, len = responseHeaders.size(); i < len; i++) {
            final String name = responseHeaders.name(i), value = responseHeaders.value(i);
            if (name != null) {
                response.addHeader(new BasicHeader(name, value));
            }
        }

        return response;
    }

    private static HttpEntity entityFromOkHttpResponse(Response r) throws IOException {
        BasicHttpEntity entity = new BasicHttpEntity();
        ResponseBody body = r.body();

        entity.setContent(body.byteStream());
        entity.setContentLength(body.contentLength());
        entity.setContentEncoding(r.header("Content-Encoding"));

        if (body.contentType() != null) {
            entity.setContentType(body.contentType().type());
        }
        return entity;
    }

    private static void setConnectionParametersForRequest(okhttp3.Request.Builder builder, com.android.volley.Request<?> request)
            throws IOException, AuthFailureError {
        switch (request.getMethod()) {
            case Request.Method.DEPRECATED_GET_OR_POST:
                // Ensure backwards compatibility.  Volley assumes a request with a null body is a GET.
                byte[] postBody = request.getPostBody();
                if (postBody != null) {
                    builder.post(RequestBody.create(MediaType.parse(request.getPostBodyContentType()), postBody));
                }
                break;
            case Request.Method.GET:
                builder.get();
                break;
            case Request.Method.DELETE:
                builder.delete();
                break;
            case Request.Method.POST:
                builder.post(createRequestBody(request));
                break;
            case Request.Method.PUT:
                builder.put(createRequestBody(request));
                break;
            case Request.Method.HEAD:
                builder.head();
                break;
            case Request.Method.OPTIONS:
                builder.method("OPTIONS", null);
                break;
            case Request.Method.TRACE:
                builder.method("TRACE", null);
                break;
            case Request.Method.PATCH:
                builder.patch(createRequestBody(request));
                break;
            default:
                throw new IllegalStateException("Unknown method type.");
        }
    }

    private static ProtocolVersion parseProtocol(final Protocol p) {
        switch (p) {
            case HTTP_1_0:
                return new ProtocolVersion("HTTP", 1, 0);
            case HTTP_1_1:
                return new ProtocolVersion("HTTP", 1, 1);
            case SPDY_3:
                return new ProtocolVersion("SPDY", 3, 1);
            case HTTP_2:
                return new ProtocolVersion("HTTP", 2, 0);
        }

        throw new IllegalAccessError("Unkwown protocol");
    }

    private static RequestBody createRequestBody(Request r) throws AuthFailureError {
        final byte[] body = r.getBody();
        if (body == null) {
            //avoid empty body that will throw IllegalArgumentException if the params is empty,
            //so we will return RequestBody.create(MediaType.parse(r.getBodyContentType()), "") instead of null
            return RequestBody.create(MediaType.parse(r.getBodyContentType()), "");
        }

        return RequestBody.create(MediaType.parse(r.getBodyContentType()), body);
    }

    //cancel requests based on tag
    public void cancelRequestOnGoing(Object tag) {
        if (sOkHttpClient != null) {
            for (Call call : sOkHttpClient.dispatcher().queuedCalls()) {
                if (call.request().tag().equals(tag))
                    call.cancel();
            }
            for (Call call : sOkHttpClient.dispatcher().runningCalls()) {
                if (call.request().tag().equals(tag))
                    call.cancel();
            }
        }
    }

}

VolleySingleton.java

import android.content.Context;

import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.toolbox.Volley;

public class VolleySingleton {
    private static VolleySingleton mInstance = null;
    private RequestQueue mRequestQueue;
    //private ImageLoader mImageLoader;
    //private ImageLoader.ImageCache mImageCache;
    private OkHttp3Stack mOkHttp3Stack;
    private static final String TAG = VolleySingleton.class.getSimpleName();

    private VolleySingleton(Context context) {
        //use okhttp stack
        mOkHttp3Stack = new OkHttp3Stack();
        mRequestQueue = Volley.newRequestQueue(context, mOkHttp3Stack);

        //default
        //mRequestQueue = Volley.newRequestQueue(context);

        //initiateImageLoader();
    }

//    private void initiateImageLoader(){
//        mImageCache = new ImageLoader.ImageCache() {
//            // int cacheSize = 1024 * 1024 * 10;
//            private final BitmapLruCache mCache = new BitmapLruCache();
//
//            public void putBitmap(String url, Bitmap bitmap) {
//                mCache.put(url, bitmap);
//            }
//
//            public Bitmap getBitmap(String url) {
//                return mCache.get(url);
//            }
//        };
//        mImageLoader = new ImageLoader(this.mRequestQueue, mImageCache);
//    }

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

    private RequestQueue getRequestQueue() {
        return this.mRequestQueue;
    }

//    public ImageLoader getImageLoader() {
//        return this.mImageLoader;
//    }

//    public ImageLoader.ImageCache getImageCache() {
//        return this.mImageCache;
//    }

    /**
     * Helper classes
     */
    public <T> void addToRequestQueue(Request<T> req, Object tag) {
        // set the default tag if tag is empty
        req.setTag(tag == null ? TAG : tag);
        getRequestQueue().add(req);
    }

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

    public void cancelPendingRequests(Object tag) {
        if (mRequestQueue != null) {
            mRequestQueue.cancelAll(tag);
            mOkHttp3Stack.cancelRequestOnGoing(tag);
        }
    }

    public void cancelPendingRequestsNoTag() {
        if (mRequestQueue != null) {
            mRequestQueue.cancelAll(TAG);
            mOkHttp3Stack.cancelRequestOnGoing(TAG);
        }
    }

    public void clearVolleyCache() {
        if (mRequestQueue != null) {
            mRequestQueue.getCache().clear();
        }
    }
    /**
     * End helper classes
     */
}