How to start an app the same way Android Launcher does (resume)

Question

There are a lot of questions/answers about how to start an application from within your application in Android. But those solutions do not produce the same flow as if an icon was tapped in Android launcher. For example, I do this (this is used with notifications):

intent = context.getPackageManager().getLaunchIntentForPackage("com.test.startup");
intent.setAction(Intent.ACTION_MAIN);
intent.addCategory(Intent.CATEGORY_LAUNCHER);
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

pendingIntent = PendingIntent.getActivity(context, 0,
            intent, PendingIntent.FLAG_UPDATE_CURRENT);

Then when I tap on notification the app is started, however, it is started somewhat differently than when I tap the icon in the App drawer. Specifically: with this approach my main Activity is always created (i.e. onCreate() then onResume() is called). However, if application was already started and then put in background, then starting it from Launcher will only cause onResume() of currently shown activity to be called (not onCreate() on the main one). Is there a way to trigger the same resume flow programmatically from within my app?

To summarize the task: when user taps on notification I need my app to be either started (if it's not already), or brought to the foreground in its current state (if it's in background) and have some data passed to it. The app will then take care of handling/rendering that data.

Answer 1

Your app is behaving the way it supposed to. Even if you try the launch the app from App drawer it will call the same callback. You have to understand the lifecycle. As your activity is in the background onCreate will not get called. But for the handling the data from the notification intent you should utilize callback method OnNewIntent() in activity. You should override this method and extract the data the from the new intent and should update UI. After onNewIntent onresume will be called. I hope this solves your problem.

Answer 2

Here is my onPause code which works the way you expected i.e when user clicks on the notification it doesnt call onCreate again:

notificationManager = (NotificationManager)getSystemService(NOTIFICATION_SERVICE); 
        intent = new Intent(getApplicationContext(), PlayerActivity.class);     
        intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP| Intent.FLAG_ACTIVITY_SINGLE_TOP);
        PendingIntent pIntent = PendingIntent.getActivity(getBaseContext(), 0, intent,0);
        NotificationCompat.Builder noti =
                new NotificationCompat.Builder(this)
                .setSmallIcon(android.R.drawable.ic_media_play)
                .setContentTitle("Nepali Music And more")
                .setContentText("Playing");
    noti.setContentIntent(pIntent);
    noti.setAutoCancel(true);
    noti.setOngoing(true);
     Notification notification = noti.getNotification();


        notificationManager.notify(1, notification);

Focus mainly on the intent flags

Answer 3

You want to use the intent flags Intent.FLAG_ACTIVITY_CLEAR_TOP to find your activity and clear the stack above it. You also need the Intent.FLAG_ACTIVITY_SINGLE_TOP flag to prevent your activity from being recreated (to resume).

The Intent.FLAG_ACTIVITY_SINGLE_TOP is necessary since by default, the launch mode is "standard" which lets you create multiple instances of your activity. If you were to set your launch mode to SingleTop, then this flag own't be necessary