Question

我正在尝试通过每次请求失败时使用handler.postDelayed(...)调度线程来重试失败的http调用来实现指数退避。问题是我从IntentService这样做，它在调度第一个线程后死亡，因此处理程序无法调用自身。我收到以下错误：

java.lang.IllegalStateException: Handler (android.os.Handler) {2f31b19b} sending message to a Handler on a dead thread

我使用IntentService的课程：

@Override
    protected void onHandleIntent(Intent intent) {

        ......

        Handler handler = new Handler();
        HttpRunnable httpRunnable = new HttpRunnable(info, handler);
        handler.postDelayed(httpRunnable, 0);

}

我的自定义Runnable：

public class HttpRunnable implements Runnable {

  private String info;
  private static final String TAG = "HttpRunnable";
  Handler handler = null;
  int maxTries = 10;
  int retryCount = 0;
  int retryDelay = 1000; // Set the first delay here which will increase exponentially with each retry

  public HttpRunnable(String info, Handler handler) {
    this.info = info;
    this.handler = handler;
  }

  @Override
  public void run() {
    try {
        // Call my class which takes care of the http call
        ApiBridge.getInstance().makeHttpCall(info);
    } catch (Exception e) {
        Log.d(TAG, e.toString());
        if (maxTries > retryCount) {
        Log.d(TAG,"%nRetrying in " + retryDelay / 1000 + " seconds");
            retryCount++;
            handler.postDelayed(this, retryDelay);
            retryDelay = retryDelay * 2;
        }
    }
  }
}

有没有办法让我的处理程序保持活力？以指数退避方式安排我的http重试的最佳/最干净方法是什么？

Answer 1

使用IntentService的主要优点是它可以在其onHandleIntent(Intent intent)方法中处理所有背景线程。在这种情况下，您没有理由自己管理处理程序。

在这里，您可以使用AlarmManager来安排向服务传递意图。您可以将重试信息保留在要传递的意图中。

我在想这样的事情：

public class YourService extends IntentService {

    private static final String EXTRA_FAILED_ATTEMPTS = "com.your.package.EXTRA_FAILED_ATTEMPTS";
    private static final String EXTRA_LAST_DELAY = "com.your.package.EXTRA_LAST_DELAY";
    private static final int MAX_RETRIES = 10;
    private static final int RETRY_DELAY = 1000;

    public YourService() {
        super("YourService");
    }

    @Override
    protected final void onHandleIntent(Intent intent) {

        // Your other code obtaining your info string.

        try {
            // Make your http call.
            ApiBridge.getInstance().makeHttpCall(info);
        } catch (Exception e) {
            // Get the number of previously failed attempts, and add one.
            int failedAttempts = intent.getIntExtra(EXTRA_FAILED_ATTEMPTS, 0) + 1;
            // if we have failed less than the max retries, reschedule the intent
            if (failedAttempts < MAX_RETRIES) {
                // calculate the next delay
                int lastDelay = intent.getIntExtra(EXTRA_LAST_DELAY, 0);
                int thisDelay;
                if (lastDelay == 0) {
                    thisDelay = RETRY_DELAY;
                } else {
                    thisDelay = lastDelay * 2;
                }
                // update the intent with the latest retry info
                intent.putExtra(EXTRA_FAILED_ATTEMPTS, failedAttempts);
                intent.putExtra(EXTRA_LAST_DELAY, thisDelay);
                // get the alarm manager
                AlarmManager alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE);
                // make the pending intent
                PendingIntent pendingIntent = PendingIntent
                        .getService(getApplicationContext(), 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);
                // schedule the intent for future delivery
                alarmManager.set(AlarmManager.RTC_WAKEUP,
                        System.currentTimeMillis() + thisDelay, pendingIntent);
            }
        }
    }
}

这简单地让你正在使用的IntentService在后台执行调用，然后在每次失败时调度要重新发送的意图，为它添加额外的次数，重试次数以及重试多长时间最后的重试延迟是。

注意：如果您尝试向此服务发送多个意图并且多个意图失败并且必须使用AlarmManager重新安排，则只有根据{{认为意图相等才会传递最新意图1}}。如果您的意图与附加的附加内容相同，则这将是一个问题，并且您必须在创建Intent.filterEquals(Intent intent)时为每个重新安排的意图使用唯一的requestCode。这些方面的东西：

PendingIntent

我想您可以使用共享首选项来存储请求代码，每次必须安排重试时，该代码会递增。

从IntentService调度递归处理程序以重试http调用

1 个答案: