Android onHandleIntent IntentService waits for UI Thread

Question

I noticed that if i call startService from UI thread, onHandleIntent is not called until after UI thread is released. ie onHandleIntent is blocked by UI Thread. I tried calling startService in a AsyncTask, still onHandleIntent call is blocked until UI thread is released. Is this is a behavior (or bug ??) in Android ? or I am doing anything wrong? I am testing it in Android 6.0.

Here is my Intent Service

public class TestIntentService extends IntentService {

     private static final String TAG = TestIntentService.class.getSimpleName();

     public TestIntentService() {
          super(TAG);
     }

     @Override
     protected void onHandleIntent(Intent intent) {
          Log.d(TAG, "onHandleIntent Called");

          try {
               for (int i = 1; i <= 10; i++) {
                   Thread.sleep(1000);
                   Log.d(TAG, "onHandleIntent After " + i + " seconds");
               }

               synchronized (MainActivity.handle) {
                    MainActivity.handle.notify();
               }

          } catch (Exception e) {
               Log.e(TAG, "Exception", e);
          }
     }
}

Here is the method in my Activity that will be called on click of a button where I am calling start Service

protected void onStartServiceButtonClicked(View view) {
    Log.d(TAG, "startServiceClicked");

    Intent intent = new Intent(context,  TestIntentService.class);
    startService(intent);
    Log.d(TAG, "After calling startService");


    synchronized (handle) {
        try {
            Log.d(TAG, "Before waiting");
            handle.wait(4000);
            Log.d(TAG, "After handler Wait");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

    }
}

and handle is just an activity class member variable public static Object handle = new Object();

Here is the adb log

08-24 10:06:27.777 13564-13564/com.kl.testintentservice D/MainActivity: startServiceClicked
08-24 10:06:27.778 13564-13564/com.kl.testintentservice D/MainActivity: After calling startService
08-24 10:06:27.778 13564-13564/com.kl.testintentservice D/MainActivity: Before waiting
08-24 10:06:31.778 13564-13564/com.kl.testintentservice D/MainActivity: After handler Wait
08-24 10:06:31.782 13564-13564/com.kl.testintentservice I/Choreographer: Skipped 252 frames!  The application may be doing too much work on its main thread.
08-24 10:06:31.783 13564-16520/com.kl.testintentservice D/TestIntentService: onHandleIntent Called
08-24 10:06:32.784 13564-16520/com.kl.testintentservice D/TestIntentService: onHandleIntent After 1 seconds
08-24 10:06:33.784 13564-16520/com.kl.testintentservice D/TestIntentService: onHandleIntent After 2 seconds
08-24 10:06:34.785 13564-16520/com.kl.testintentservice D/TestIntentService: onHandleIntent After 3 seconds
08-24 10:06:35.786 13564-16520/com.kl.testintentservice D/TestIntentService: onHandleIntent After 4 seconds
08-24 10:06:36.786 13564-16520/com.kl.testintentservice D/TestIntentService: onHandleIntent After 5 seconds
08-24 10:06:37.786 13564-16520/com.kl.testintentservice D/TestIntentService: onHandleIntent After 6 seconds
08-24 10:06:38.786 13564-16520/com.kl.testintentservice D/TestIntentService: onHandleIntent After 7 seconds
08-24 10:06:39.787 13564-16520/com.kl.testintentservice D/TestIntentService: onHandleIntent After 8 seconds
08-24 10:06:40.787 13564-16520/com.kl.testintentservice D/TestIntentService: onHandleIntent After 9 seconds
08-24 10:06:41.787 13564-16520/com.kl.testintentservice D/TestIntentService: onHandleIntent After 10 seconds
08-24 10:06:41.787 13564-16520/com.kl.testintentservice D/TestIntentService: handle notified

Answer 1

This behavior is perfectly normal. It is not unique to IntentService . Any startActivity() , startService() , bindService() , or sendBroadcast() call will not even begin doing its work until you return from whatever main application thread callback you are on.

Since tying up the main application thread in a callback for more than 1ms is poor practice, this behavior should not impact very many developers.