Android: Clear the back stack

Question

In Android I have some activities, let's say A, B, C.

In A, I use this code to open B:

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

In B, I use this code to open C:

Intent intent = new Intent(this, C.class);
startActivity(intent);

When the user taps a button in C, I want to go back to A and clear the back stack (close both B and C). So when the user use the back button B and C will not show up, I've been trying the following:

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

But B and C are still showing up if I use the back button when I'm back in activity A. How can I avoid this?

Solution 1

Try adding FLAG_ACTIVITY_NEW_TASK as described in the docs for FLAG_ACTIVITY_CLEAR_TOP:

This launch mode can also be used to good effect in conjunction with FLAG_ACTIVITY_NEW_TASK: if used to start the root activity of a task, it will bring any currently running instance of that task to the foreground, and then clear it to its root state. This is especially useful, for example, when launching an activity from the notification manager.

So your code to launch A would be:

Intent intent = new Intent(this, A.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_NEW_TASK); 
startActivity(intent);
CurrentActivity.this.finish(); // if the activity running has it's own context


// view.getContext().finish() for fragments etc.

Solution 2

intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
startActivity(intent);

Solution 3

What about adding in manifests file for related activity :

android:noHistory="true"

to the activity definition of B and C ? They will not be added to the backstack. Not sure if that is what you want.

Solution 4

This bothers me for a long time .Finally I worked it out by doing this:

In fragment,use:

Intent intent = new Intent(view.getContext(), A.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_NEW_TASK); 
startActivity(intent);

In Activity,use(add one more intent flag Intent.FLAG_ACTIVITY_CLEAR_TASK compared to fragment):

Intent intent = new Intent(this, MainActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);

Solution 5

1. Add android:launchMode="singleTop" to the activity element in your manifest for Activity A
2. Then use intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP) and intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK) when starting Activity A

This means that when Activity A is launched, all tasks on top of it are cleared so that A is top. A new back stack is created with A at the root, and using singleTop ensures you only ever launch A once (since A is now on top due to ..._CLEAR_TOP).

View more solutions