原文連結
A HttpStack implementation for Volley that uses OkHttp as its transport.

/**
 * The MIT License (MIT)
 *
 * Copyright (c) 2015 Circle Internet Financial
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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 * THE SOFTWARE.
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import com.android.volley.AuthFailureError;
import com.android.volley.Request;
import com.android.volley.toolbox.HttpStack;
import com.squareup.okhttp.Call;
import com.squareup.okhttp.Headers;
import com.squareup.okhttp.MediaType;
import com.squareup.okhttp.OkHttpClient;
import com.squareup.okhttp
 
.Protocol;
import com.squareup.okhttp.RequestBody;
import com.squareup.okhttp.Response;
import com.squareup.okhttp.ResponseBody;

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 java.util.concurrent.TimeUnit;


/**
 * OkHttp backed {@link com.android.volley.toolbox.HttpStack HttpStack} that does not
 * use okhttp-urlconnection
 */
public class OkHttpStack implements HttpStack {

    private final OkHttpClient mClient;

    public OkHttpStack(OkHttpClient client) {
        this.mClient = client;
    }

    @Override
    public HttpResponse performRequest(Request<?> request, Map<String, String> additionalHeaders)
            throws IOException, AuthFailureError {

        OkHttpClient client = mClient.clone();
        int timeoutMs = request.getTimeoutMs();
        client.setConnectTimeout(timeoutMs, TimeUnit.MILLISECONDS);
        client.setReadTimeout(timeoutMs, TimeUnit.MILLISECONDS);
        client.setWriteTimeout(timeoutMs, TimeUnit.MILLISECONDS);

        com.squareup.okhttp.Request.Builder okHttpRequestBuilder = new com.squareup.okhttp.Request.Builder();
        okHttpRequestBuilder.url(request.getUrl());

        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);

        com.squareup.okhttp.Request okHttpRequest = okHttpRequestBuilder.build();
        Call okHttpCall = client.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;
    }

    @SuppressWarnings("deprecation")
    private static void setConnectionParametersForRequest(com.squareup.okhttp.Request.Builder builder, 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) return null;

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

如果使用了Stetho，那麼應該再引入

compile 'com.facebook.stetho:stetho-okhttp:1.1.1'

然後新增StethoInterceptor，如下

mOkHttpClient.networkInterceptors().add(new StethoInterceptor());
        mRequestQueue = Volley.newRequestQueue(context, new OkHttpStack(mOkHttpClient));