RequestQueue queue = Volley.newRequestQueue(this); //实例化一个请求队列 Google推荐写一个单例类 获取唯一一个队列  
 StringRequest request = new StringRequest(Request.Method.POST, url1, new Response.Listener<String>() { 
      @Override 
      public void onResponse(String response) { 
        Toast.makeText(MainActivity.this, "success"+response, Toast.LENGTH_SHORT).show(); 
      } 
    }, new Response.ErrorListener() { 
      @Override 
      public void onErrorResponse(VolleyError error) { 
        Toast.makeText(MainActivity.this, "失败了"+error.getMessage(), Toast.LENGTH_SHORT).show(); 
      } 
    }){ 
      @Override 
      protected Map<String, String> getParams() throws AuthFailureError { //重写这个函数提交参数 也可以重写一个Request实现这个方法 
        Map<String,String> params = new HashMap<>(); 
        params.put(aaa+"name","1233555"); //参数 
        return params; 
      } 
    }; 
    queue.add(request); 

public <T> Request<T> add(Request<T> request) { 
  // Tag the request as belonging to this queue and add it to the set of current requests. 
  request.setRequestQueue(this);  
  synchronized (mCurrentRequests) { 
    mCurrentRequests.add(request);  //在当前队列中加入 
  } 
 
  // Process requests in the order they are added. 
  request.setSequence(getSequenceNumber()); 
  request.addMarker("add-to-queue"); //设置标志 
 
  // If the request is uncacheable, skip the cache queue and go straight to the network. 
  if (!request.shouldCache()) { //根据是否需要缓存 如果不需要缓存 就直接加入网络任务队列中 然后返回 如果需要缓存 那么在下面代码中加入缓存队列 默认是需要缓存的  
    mNetworkQueue.add(request); 
    return request; 
  } 
 
  // Insert request into stage if there's already a request with the same cache key in flight. 
  synchronized (mWaitingRequests) { 
    String cacheKey = request.getCacheKey(); 
    if (mWaitingRequests.containsKey(cacheKey)) { //判断当前正在被处理并可以缓存的请求中是否包含该请求的key 如果包含说明已经有一个相同的请求 那么就加入到其中 
      // There is already a request in flight. Queue up. 
      Queue<Request<?>> stagedRequests = mWaitingRequests.get(cacheKey); 
      if (stagedRequests == null) { 
        stagedRequests = new LinkedList<Request<?>>(); 
      } 
      stagedRequests.add(request); 
      mWaitingRequests.put(cacheKey, stagedRequests); 
      if (VolleyLog.DEBUG) { 
        VolleyLog.v("Request for cacheKey=%s is in flight, putting on hold.", cacheKey); 
      } 
    } else { //如果不包含 加入一个空的请求到 暂存队列中 然后加入到缓存队列中  
      // Insert 'null' queue for this cacheKey, indicating there is now a request in 
      // flight. 
      mWaitingRequests.put(cacheKey, null);  
      mCacheQueue.add(request); 
    } 
    return request; 
  } 
} 

public static RequestQueue newRequestQueue(Context context, HttpStack stack) { 
    File cacheDir = new File(context.getCacheDir(), DEFAULT_CACHE_DIR); //创建一个文件用于缓存 
 
    String userAgent = "volley/0";  //用户代理初始化  
    try { 
      String packageName = context.getPackageName(); 
      PackageInfo info = context.getPackageManager().getPackageInfo(packageName, 0); 
      userAgent = packageName + "/" + info.versionCode; //用户代理为app包名+版本号 
    } catch (NameNotFoundException e) { 
    } 
 
    if (stack == null) { //如果没传入HttpStack 那么采用下述默认的  这里可以自行重写扩展HttpStack 体现了该框架的高扩展性   
      if (Build.VERSION.SDK_INT >= 9) { //如果sdk版本高于2.3 采用HurlStack 内部是httpUrlConnection实现  
        stack = new HurlStack(); 
      } else { //如果版本低于2.3 采用httpClientStack  
        // Prior to Gingerbread, HttpUrlConnection was unreliable. 
        // See: http://android-developers.blogspot.com/2011/09/androids-http-clients.html 
        stack = new HttpClientStack(AndroidHttpClient.newInstance(userAgent)); 
      } 
    } 
 
    Network network = new BasicNetwork(stack); //创建一个网络工作 仅仅作用于请求网络  
 
    RequestQueue queue = new RequestQueue(new DiskBasedCache(cacheDir), network); //实例化一个请求队列 传入参数 
    queue.start(); 
 
    return queue; 
  } 

</pre><pre code_snippet_id="1680121" snippet_file_name="blog_20160512_5_2241745" name="code" class="java">public RequestQueue(Cache cache, Network network, int threadPoolSize) { //构造函数 会创建默认的ExecutorDelivery 用于回调 
    this(cache, network, threadPoolSize, 
        new ExecutorDelivery(new Handler(Looper.getMainLooper()))); 
  } 

public void start() { 
    stop(); // Make sure any currently running dispatchers are stopped. 
    // Create the cache dispatcher and start it. 
    mCacheDispatcher = new CacheDispatcher(mCacheQueue, mNetworkQueue, mCache, mDelivery); //创建一个缓存调度器 是一个线程 start后执行run方法 
    mCacheDispatcher.start(); 
 
    // Create network dispatchers (and corresponding threads) up to the pool size. 
    for (int i = 0; i < mDispatchers.length; i++) { //默认会有4个NetworkDispatcher 为了提高效率 执行netWorkQueue里的request 
      NetworkDispatcher networkDispatcher = new NetworkDispatcher(mNetworkQueue, mNetwork, 
          mCache, mDelivery); 
      mDispatchers[i] = networkDispatcher; 
      networkDispatcher.start(); 
    } 
  } 

@Override 
 public void run() { 
   if (DEBUG) VolleyLog.v("start new dispatcher"); 
   Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND); //设置线程的优先级  值为10 
 
   // Make a blocking call to initialize the cache. 
   mCache.initialize(); //初始化一下缓存  
 
   while (true) { 
     try { 
       // Get a request from the cache triage queue, blocking until 
       // at least one is available. 
       final Request<?> request = mCacheQueue.take();  //从缓存队列取出一个请求 如果没有则会阻塞  
       request.addMarker("cache-queue-take");  //添加一个标记 
 
       // If the request has been canceled, don't bother dispatching it. 
       if (request.isCanceled()) {   
         request.finish("cache-discard-canceled"); 
         continue; 
       } 
 
       // Attempt to retrieve this item from cache. 
       Cache.Entry entry = mCache.get(request.getCacheKey()); //从缓存中读取缓存  
       if (entry == null) { //如果没读取到缓存  
         request.addMarker("cache-miss"); //添加缓存miss标记   
         // Cache miss; send off to the network dispatcher.  
         mNetworkQueue.put(request); //换区缓存失败 添加到netWork中等待请求 
         continue; 
       } 
 
       // If it is completely expired, just send it to the network. 
       if (entry.isExpired()) { //判断缓存是否过期了 如果过期了 那么就添加到netWork中等待请求  
         request.addMarker("cache-hit-expired"); 
         request.setCacheEntry(entry); 
         mNetworkQueue.put(request); 
         continue; 
       } 

// We have a cache hit; parse its data for delivery back to the request. 
        request.addMarker("cache-hit"); //执行到了这里说明缓存没有过期 并且可以使用  
        Response<?> response = request.parseNetworkResponse( //把读取到的缓存内容解析成Response对象  
            new NetworkResponse(entry.data, entry.responseHeaders)); 
        request.addMarker("cache-hit-parsed"); //添加标记 
 
        if (!entry.refreshNeeded()) { //如果缓存不需要刷新 直接调用 mDelivery.postResponse方法  在其中会回调request的listener接口 
          // Completely unexpired cache hit. Just deliver the response. 
          mDelivery.postResponse(request, response); 
        } else { //如果需要刷新  把请求加入mNetworkQueue中 等待请求 
          // Soft-expired cache hit. We can deliver the cached response, 
          // but we need to also send the request to the network for 
          // refreshing. 
          request.addMarker("cache-hit-refresh-needed"); 
          request.setCacheEntry(entry); 
 
          // Mark the response as intermediate. 
          response.intermediate = true; 
 
          // Post the intermediate response back to the user and have 
          // the delivery then forward the request along to the network. 
          mDelivery.postResponse(request, response, new Runnable() {   
            @Override 
            public void run() { 
              try { 
                mNetworkQueue.put(request); 
              } catch (InterruptedException e) { 
                // Not much we can do about this. 
              } 
            } 
          }); 
        } 
 
      } catch (InterruptedException e) { 
        // We may have been interrupted because it was time to quit. 
        if (mQuit) { 
          return; 
        } 
        continue; 
      } 
    } 
  } 

@Override 
  public void run() { 
    Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND); //设置优先级 10 
    while (true) { 
      long startTimeMs = SystemClock.elapsedRealtime(); //获取请求执行开始时间 
      Request<?> request; 
      try { 
        // Take a request from the queue. 
        request = mQueue.take(); //从队列获取一个请求 没有则阻塞  
      } catch (InterruptedException e) { 
        // We may have been interrupted because it was time to quit. 
        if (mQuit) { 
          return; 
        } 
        continue; 
      } 
 
      try { 
        request.addMarker("network-queue-take"); 
 
        // If the request was cancelled already, do not perform the 
        // network request. 
        if (request.isCanceled()) {   
          request.finish("network-discard-cancelled"); 
          continue; 
        } 
 
        addTrafficStatsTag(request);  
 
        // Perform the network request. 
        NetworkResponse networkResponse = mNetwork.performRequest(request); //真正执行请求的函数  并返回响应 
        request.addMarker("network-http-complete"); 
 
        // If the server returned 304 AND we delivered a response already, 
        // we're done -- don't deliver a second identical response. 
        if (networkResponse.notModified && request.hasHadResponseDelivered()) {  
          request.finish("not-modified"); 
          continue; 
        } 
 
        // Parse the response here on the worker thread. 
        Response<?> response = request.parseNetworkResponse(networkResponse); //解析响应  
        request.addMarker("network-parse-complete"); 
 
        // Write to cache if applicable. 
        // TODO: Only update cache metadata instead of entire record for 304s. 
        if (request.shouldCache() && response.cacheEntry != null) { //如果需要缓存 那么把响应的信息存入缓存中  
          mCache.put(request.getCacheKey(), response.cacheEntry); 
          request.addMarker("network-cache-written"); 
        } 
 
        // Post the response back. 
        request.markDelivered(); 
        mDelivery.postResponse(request, response); //之后回调一些方法  
      } catch (VolleyError volleyError) { 
        volleyError.setNetworkTimeMs(SystemClock.elapsedRealtime() - startTimeMs); 
        parseAndDeliverNetworkError(request, volleyError); //回调错误接口  
      } catch (Exception e) { 
        VolleyLog.e(e, "Unhandled exception %s", e.toString()); 
        VolleyError volleyError = new VolleyError(e); 
        volleyError.setNetworkTimeMs(SystemClock.elapsedRealtime() - startTimeMs); 
        mDelivery.postError(request, volleyError);  //回调错误接口 
      } 
    } 
  } 

@Override 
  public NetworkResponse performRequest(Request<?> request) throws VolleyError { 
    long requestStart = SystemClock.elapsedRealtime(); //记录开始时间  
    while (true) { 
      HttpResponse httpResponse = null;  
      byte[] responseContents = null; 
      Map<String, String> responseHeaders = Collections.emptyMap(); //初始化响应头为空  
      try { 
        // Gather headers. 
        Map<String, String> headers = new HashMap<String, String>(); //请求头  
        addCacheHeaders(headers, request.getCacheEntry()); //根据缓存添加请求头  
        httpResponse = mHttpStack.performRequest(request, headers); //调用HttpStack的方法请求网络  
        StatusLine statusLine = httpResponse.getStatusLine(); 
        int statusCode = statusLine.getStatusCode(); 
 
        responseHeaders = convertHeaders(httpResponse.getAllHeaders()); //获取响应头  
        // Handle cache validation. 
        if (statusCode == HttpStatus.SC_NOT_MODIFIED) {  //如果为304 读取的缓存  
 
          Entry entry = request.getCacheEntry(); //查看以前是否缓存过  
          if (entry == null) { //如果以前缓存的为空 那么 说明上次缓存的请求也为空 直接返回response 
            return new NetworkResponse(HttpStatus.SC_NOT_MODIFIED, null, 
                responseHeaders, true, 
                SystemClock.elapsedRealtime() - requestStart); 
          } 
 
          // A HTTP 304 response does not have all header fields. We 
          // have to use the header fields from the cache entry plus 
          // the new ones from the response. 
          // http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.3.5 
          entry.responseHeaders.putAll(responseHeaders); //如果不空 那么就添加头 然后返回 数据了  
          return new NetworkResponse(HttpStatus.SC_NOT_MODIFIED, entry.data, 
              entry.responseHeaders, true, 
              SystemClock.elapsedRealtime() - requestStart); 
        } 
 
        // Some responses such as 204s do not have content. We must check. 
        if (httpResponse.getEntity() != null) { //不是304的情况  

     responseContents = entityToBytes(httpResponse.getEntity()); //获取响应的内容 下面返回响应即可  
    } else { 
     // Add 0 byte response as a way of honestly representing a 
     // no-content request. 
     responseContents = new byte[0]; 
    } 
 
    // if the request is slow, log it. 
    long requestLifetime = SystemClock.elapsedRealtime() - requestStart; 
    logSlowRequests(requestLifetime, request, responseContents, statusLine); 
 
    if (statusCode < 200 || statusCode > 299) { 
      throw new IOException(); 
    } 
    return new NetworkResponse(statusCode, responseContents, responseHeaders, false, 
        SystemClock.elapsedRealtime() - requestStart); 
  } catch (SocketTimeoutException e) { 
    attemptRetryOnException("socket", request, new TimeoutError()); 
  } catch (ConnectTimeoutException e) { 
    attemptRetryOnException("connection", request, new TimeoutError()); 
  } catch (MalformedURLException e) { 
    throw new RuntimeException("Bad URL " + request.getUrl(), e); 
  } catch (IOException e) { 
    int statusCode = 0; 
    NetworkResponse networkResponse = null; 
    if (httpResponse != null) { 
      statusCode = httpResponse.getStatusLine().getStatusCode(); 
    } else { 
      throw new NoConnectionError(e); 
    } 
    VolleyLog.e("Unexpected response code %d for %s", statusCode, request.getUrl()); 
    if (responseContents != null) { 
      networkResponse = new NetworkResponse(statusCode, responseContents, 
          responseHeaders, false, SystemClock.elapsedRealtime() - requestStart); 
      if (statusCode == HttpStatus.SC_UNAUTHORIZED || 
          statusCode == HttpStatus.SC_FORBIDDEN) { 
        attemptRetryOnException("auth", 
            request, new AuthFailureError(networkResponse)); 
      } else { 
        // TODO: Only throw ServerError for 5xx status codes. 
        throw new ServerError(networkResponse); 
      } 
    } else { 
      throw new NetworkError(networkResponse); 
    } 
  } 
} 

@Override 
  public HttpResponse performRequest(Request<?> request, Map<String, String> additionalHeaders) 
      throws IOException, AuthFailureError { 
    String url = request.getUrl(); 
    HashMap<String, String> map = new HashMap<String, String>(); 
    map.putAll(request.getHeaders()); //添加请求头   
    map.putAll(additionalHeaders); 
    if (mUrlRewriter != null) { 
      String rewritten = mUrlRewriter.rewriteUrl(url); 
      if (rewritten == null) { 
        throw new IOException("URL blocked by rewriter: " + url); 
      } 
      url = rewritten; 
    } 
    URL parsedUrl = new URL(url); 
    HttpURLConnection connection = openConnection(parsedUrl, request); //打开连接  
    for (String headerName : map.keySet()) { //设置头  
      connection.addRequestProperty(headerName, map.get(headerName)); 
    } 
    setConnectionParametersForRequest(connection, request); //在这个函数里添加请求的参数 和一些基本的信息配置  
    // Initialize HttpResponse with data from the HttpURLConnection. 
    ProtocolVersion protocolVersion = new ProtocolVersion("HTTP", 1, 1); 
    int responseCode = connection.getResponseCode(); //下面就是些获取响应信息后的处理了  
    if (responseCode == -1) { 
      // -1 is returned by getResponseCode() if the response code could not be retrieved. 
      // Signal to the caller that something was wrong with the connection. 
      throw new IOException("Could not retrieve response code from HttpUrlConnection."); 
    } 
    StatusLine responseStatus = new BasicStatusLine(protocolVersion, 
        connection.getResponseCode(), connection.getResponseMessage()); 
    BasicHttpResponse response = new BasicHttpResponse(responseStatus); 
    response.setEntity(entityFromConnection(connection)); 
    for (Entry<String, List<String>> header : connection.getHeaderFields().entrySet()) { 
      if (header.getKey() != null) { 
        Header h = new BasicHeader(header.getKey(), header.getValue().get(0)); 
        response.addHeader(h); 
      } 
    } 
    return response; 
  } 

case Method.POST: 
        connection.setRequestMethod("POST"); 
        addBodyIfExists(connection, request); 
        break; 

private static void addBodyIfExists(HttpURLConnection connection, Request<?> request) 
      throws IOException, AuthFailureError { 
    byte[] body = request.getBody(); 
    if (body != null) { 
      connection.setDoOutput(true); 
      connection.addRequestProperty(HEADER_CONTENT_TYPE, request.getBodyContentType()); 
      DataOutputStream out = new DataOutputStream(connection.getOutputStream()); 
      out.write(body); 
      out.close(); 
    } 
  } 

public byte[] getBody() throws AuthFailureError { 
    Map<String, String> params = getParams(); 
    if (params != null && params.size() > 0) { 
      return encodeParameters(params, getParamsEncoding()); 
    } 
    return null; 
  } 
getParams方法 是Request需要重写的一个方法 返回值就是参数的Map集合 
[java] view plain copy 在CODE上查看代码片派生到我的代码片
private byte[] encodeParameters(Map<String, String> params, String paramsEncoding) { 
    StringBuilder encodedParams = new StringBuilder(); 
    try { 
      for (Map.Entry<String, String> entry : params.entrySet()) { 
        encodedParams.append(URLEncoder.encode(entry.getKey(), paramsEncoding)); 
        encodedParams.append('='); 
        encodedParams.append(URLEncoder.encode(entry.getValue(), paramsEncoding)); 
        encodedParams.append('&'); 
      } 
      return encodedParams.toString().getBytes(paramsEncoding); 
    } catch (UnsupportedEncodingException uee) { 
      throw new RuntimeException("Encoding not supported: " + paramsEncoding, uee); 
    } 
  }