Switch activities by PendingIntent

This is a small project to demonstrate switching between activities with the Intent.FLAG_ACTIVITY_REORDER_TO_FRONT via a normal call to startActivity is working fine, but when I send an intent with that flag in a PendingIntent and then call mPendingIntent.send() the flag seems to be ignored :-(.

Happy flow with startActivity

When you start this small app press the START ACTIVITY A button on the MainActivity. Then press the NORMAL SWITCH -> B button on activity A. The activity stack then looks like this:

  TaskRecord{217a0c5a #1150 A=nl.codestone.switchactivities U=0 sz=3}
    Run #9: ActivityRecord{12e8571b u0 nl.codestone.switchactivities/.B t1150}
    Run #8: ActivityRecord{36a1485d u0 nl.codestone.switchactivities/.A t1150}
    Run #7: ActivityRecord{1d53b477 u0 nl.codestone.switchactivities/.MainActivity t1150}

If I then press SWITCH TO ACTIVITY A the following code will be executed:

  Intent intent = new Intent(B.this, A.class);
  intent.addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
  startActivity(intent);

And the activity stack looks like this:

  TaskRecord{217a0c5a #1150 A=nl.codestone.switchactivities U=0 sz=3}
    Run #9: ActivityRecord{36a1485d u0 nl.codestone.switchactivities/.A t1150}
    Run #8: ActivityRecord{12e8571b u0 nl.codestone.switchactivities/.B t1150}
    Run #7: ActivityRecord{1d53b477 u0 nl.codestone.switchactivities/.MainActivity t1150}

Exactly what I want. You can press the NORMAL SWITCH -> A and NORMAL SWITCH -> B buttons indefinitely and the stack will remain to exist of three activities, with either A on top or B on top.

Not so happy flow with a PendingIntent send()

Okay, here's the catch. When you click the SWITCH -> B WITH PENDING INTENT button I create a pending intent like this and add it as an intent extra:

  Intent switchBackToMeIntent = getIntent();
  switchBackToMeIntent.setAction(Long.toString(System.currentTimeMillis()));
  switchBackToMeIntent.addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);

  PendingIntent pendingIntent = PendingIntent.getActivity(A.this, 0, switchBackToMeIntent, PendingIntent.FLAG_UPDATE_CURRENT);

  Intent intent = new Intent(A.this, B.class);
  intent.putExtra(B.INTENT_EXTRA_PENDINGINTENT, pendingIntent);
  intent.addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
  startActivity(intent);

All's fine here, the stack still looks like this:

  TaskRecord{217a0c5a #1150 A=nl.codestone.switchactivities U=0 sz=3}
    Run #9: ActivityRecord{12e8571b u0 nl.codestone.switchactivities/.B t1150}
    Run #8: ActivityRecord{36a1485d u0 nl.codestone.switchactivities/.A t1150}
    Run #7: ActivityRecord{1d53b477 u0 nl.codestone.switchactivities/.MainActivity t1150}

But now, when you click on the SWITCH -> A BY PENDINGINTENT.SEND() button in activity B I use the PendingIntent extra like this:

 if (mPendingIntent != null) {
     try {
         mPendingIntent.send();
     } catch (PendingIntent.CanceledException e) {
         Log.e("B", "Pending intent was cancelled", e);
     }
 }

Then the mess starts... It looks like the Intent.FLAG_ACTIVITY_REORDER_TO_FRONT flag is ignored and I get this stack:

  TaskRecord{217a0c5a #1150 A=nl.codestone.switchactivities U=0 sz=4}
    Run #10: ActivityRecord{29351389 u0 nl.codestone.switchactivities/.A t1150}
    Run #9: ActivityRecord{339095db u0 nl.codestone.switchactivities/.B t1150}
    Run #8: ActivityRecord{3fe1e11d u0 nl.codestone.switchactivities/.A t1150}
    Run #7: ActivityRecord{1d53b477 u0 nl.codestone.switchactivities/.MainActivity t1150}

When I again press the SWITCH -> B WITH PENDING INTENT button in activity A and then the SWITCH -> A BY PENDINGINTENT.SEND() button in activity B the stack starts to grow like so:

  TaskRecord{217a0c5a #1150 A=nl.codestone.switchactivities U=0 sz=5}
    Run #11: ActivityRecord{31b517ed u0 nl.codestone.switchactivities/.A t1150}
    Run #10: ActivityRecord{339095db u0 nl.codestone.switchactivities/.B t1150}
    Run #9: ActivityRecord{29351389 u0 nl.codestone.switchactivities/.A t1150}
    Run #8: ActivityRecord{3fe1e11d u0 nl.codestone.switchactivities/.A t1150}
    Run #7: ActivityRecord{1d53b477 u0 nl.codestone.switchactivities/.MainActivity t1150}

Meh... not what I want.

P.S.: I'm using clear; adb shell dumpsys activity | grep -B 1 -A 0 "Run #" to monitor the activity stack. The -B argument specifies the 'lines before' and -A the 'lines after' the matched lines to grep. And thus gives a nice single screen overview of running activities.