使用 Volley 过程中遇到的问题

本文主要介绍使用 Volley 过程中遇到的问题，错误提示：com.android.volley.NoConnectionError: java.io.InterruptedIOException，内容加载失败，问题出在重复调用queue.start()方法。

错误提示：com.android.volley.NoConnectionError: java.io.InterruptedIOException，然后就内容加载失败…

代码如下：

private void getWxpayOrderInfo() {
  StringRequest stringRequest = new StringRequest(Request.Method.POST,
  Url, new Response.Listener<String>() {
    @Override
    public void onResponse(String response) {
    }
  }, new Response.ErrorListener() {
    @Override
    public void onErrorResponse(VolleyError error) {
    }
  }) {
    @Override
    protected Map<String, String> getParams()
    throws AuthFailureError {
      // 发送请求用到的一些参数
      Map<String, String> params = new HashMap<String, String>();
      params.put("id", "nameid");
      return params;
    }
  };
  stringRequest.setRetryPolicy(new DefaultRetryPolicy(10000,
                               DefaultRetryPolicy.DEFAULT_MAX_RETRIES,
                               DefaultRetryPolicy.DEFAULT_BACKOFF_MULT));
  queue.add(stringRequest);
  //queue.start(); //经过反复调试错误就出在这里，注释掉这里就可以了
}

问题出在调用queue.start()方法之后，错误原因可以通过 Volley 源文件看到，以下是 Volley 官方文档中初始化RequestQueue的一段代码。

/**
 * Creates a default instance of the worker pool and calls {@link RequestQueue#start()} on it.
 *
 * @param context A {@link Context} to use for creating the cache dir.
 * @param stack   An {@link HttpStack} to use for the network, or null for default.
 * @return A started {@link RequestQueue} instance.
 */
public static RequestQueue newRequestQueue(Context context, HttpStack stack) {
  File cacheDir = new File(context.getCacheDir(), DEFAULT_CACHE_DIR);
  String userAgent = "volley/0";
  try {
    String packageName = context.getPackageName();
    PackageInfo info = context.getPackageManager().getPackageInfo(packageName, 0);
    userAgent = packageName + "/" + info.versionCode;
  } catch (NameNotFoundException e) {
  }
  if (stack == null) {
    if (Build.VERSION.SDK_INT >= 9) {
      stack = new HurlStack();
    } else {
      // 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);
  RequestQueue queue = new RequestQueue(new DiskBasedCache(cacheDir), network);
  queue.start();//这里需要注意，原来在请求初始化的时候就已经调用了start方法
  return queue;
}
/**
 * Starts the dispatchers in this queue.
 */
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);
  mCacheDispatcher.start();
  // Create network dispatchers (and corresponding threads) up to the pool size.
  for (int i = 0; i < mDispatchers.length; i++) {
    NetworkDispatcher networkDispatcher = new NetworkDispatcher(mNetworkQueue, mNetwork,
        mCache, mDelivery);
    mDispatchers[i] = networkDispatcher;
    networkDispatcher.start();
  }
}
/**
 * Stops the cache and network dispatchers.
 */
public void stop() {
  if (mCacheDispatcher != null) {
    mCacheDispatcher.quit();
  }
  for (int i = 0; i < mDispatchers.length; i++) {
    if (mDispatchers[i] != null) {
      mDispatchers[i].quit();
    }
  }
}
/**
* Forces this dispatcher to quit immediately.  If any requests are still in
* the queue, they are not guaranteed to be processed.
*/
public void quit() {
  mQuit = true;
  interrupt();
}
public void interrupt() {
  // Interrupt this thread before running actions so that other
  // threads that observe the interrupt as a result of an action
  // will see that this thread is in the interrupted state.
  nativeInterrupt();
  synchronized (interruptActions) {
    for (int i = interruptActions.size() - 1; i >= 0; i--) {
      interruptActions.get(i).run();
    }
  }
}

（完）