Start fragment from notification without restarting activity

Question

Title explains my issue pretty well. I have an activity running and when the application sends a notification, I want to change the active fragment in my already running activity. If MainActivity.onDestroy is called at any point, then something has gone wrong.

An example of my problem's solution is demonstrated in the Google Play Store app. When the Play Store is open in the background and another app/notification opens the Play Store app, the Play Store opens the last fragment you were on, then proceeds to load a new fragment, but never restarts the activity.

I have tried several solutions like:

viewContactsIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_SINGLE_TOP);
viewContactsIntent.setAction(Intent.ACTION_MAIN);
viewContactsIntent.addCategory(Intent.CATEGORY_LAUNCHER);

and adding android:launchMode="singleTop to MainActivity tag in manifest.

None have worked so far.

Thanks.

EDIT:

A deeper look into the code being used to build my notification.

Class viewContacts  = MainActivity.class;
Intent viewContactsIntent   = new Intent(context, viewContacts);
TaskStackBuilder sbViewContacts   = TaskStackBuilder.create(context);
sbViewContacts.addParentStack(viewContacts).addNextIntent(viewContactsIntent);
int piFlag = PendingIntent.FLAG_UPDATE_CURRENT;
PendingIntent piViewContacts  = sbViewContacts.getPendingIntent(0, piFlag);
NotificationCompat.Builder builder = new NotificationCompat.Builder(context).setContentIntent(piViewContacts);

This notification is sent from within a PhoneStateListener upon receiving a phone call.

Answer 1

Just set the activity's launchMode to single isntance:

android:launchMode="singleInstance"

And invoke startActivity with an intent without any custom flags set.

Now if the activity that's being started is already running, it will be brought to front and its onNewIntent will be called with the intent that you passed to startActivity.

Start an activity:

Intent intent = new Intent(this, OtherActivity.class);
intent.putExtra("is okay", true);
startActivity(intent);

Receive the new intent:

@Override
protected void onNewIntent(Intent intent) {
    super.onNewIntent(intent);
    Log.e(TAG, "Okay: " + intent.getBooleanExtra("is okay", false));
}