Android clear back stack between activities

Question

I have 4 activities: Activity A -> activity B -> Activity C -> activity D and I what I want to achieve is to go back from D to A and clear B and C. Is this possible?? How??

Thanks a lot.

Answer 1

If the activity being launched is already running in the current task, then instead of launching a new instance of that activity, all of the other activities on top of it will be closed and this Intent will be delivered to the (now on top) old activity as a new Intent.

Intent intent = new Intent(this, ActivityA.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent);

Read more here.

Answer 2

If the sequence of activity is fixed (A=>B=>C=>D=>A) then before launching Activity C activity you need to call finish of B, And while launching Activity D call finish of activity C.

startActivityC() 
{
    Intent intent = new Intent(this, C.class);
    ActivityB.this.finish()
    startActivity(intent);
}

From activity D to strart Activity A you can override onBack of ActivityD to start Activity A

@Override
onBack()
{

    Intent intent = new Intent(this, A.class);

    ActivityD.this.finish()
    startActivity(intent);
}

Answer 3

If your flow always follows A => B => C => D => A, you only have to avoid saving B and C in the back stack. This way, when you go back from D, the only available Activity is A.

Code to start Activity B & C:

Intent i = new Intent(...);
i.setFlags(Intent.FLAG_ACTIVITY_NO_HISTORY); // <= Don't save in back stack
startActivity(i);

Code to start Activity A & D:

Intent i = new Intent(...);
startActivity(i);