Android singleTask activity background problem

Question

I have two activites. Activity A and Activity B.

Activity A is a singleTask activity. Activity B has no extra configuration. So it is a normal activity.

When Activity A launches the activity B then if user presses to the home button then comes back immediately (so my app is not killed by android yet.) My app is showing activity A. But it should show the activity B because the user pressed to home button when active activity is B.

If i remove the singleTask property from Activity A. It is working as expected. But i have to use singleTask activity for some other reason.

How can i resolve this problem?

Answer 1

As you have constraint to use singleTask launch mode, you can do following :

1. When user press Home, app or Activity B goes in background (stopped state)
2. Then when you open app, it'll show Activity A because of singleTask launch mode
3. In Activity A, override onNewIntent() method. This will get called from android os. You can fire Activity B's intent from this method. So, system will open Activity A when coming from background to your app, but from this method, Activity B would be shown.

I've edited my answer to handle below scenario :

• If we're on ActivityA, we press Home button and we come back, ActivityA should be shown, not ActivityB. To do this, I used boolean shouldOpenB

in Activity A :

static boolean shouldOpenB = false;

// set shouldOpenB to true when you are opening ActivityB from your code with Intent

// reset shouldOpenB to false in onStart() of AcrivityA

protected void onNewIntent (Intent intent) {
    if(shouldOpenB) {
        Intent openIntentB = new Intent(this, ActivityB.class);
        startActivity(openIntentB);
    }
}

Note : The animation of Activity A -> Activity B would be visible to user for fraction of time. If you agree to change to singleTop, we can remove this animation also.