Question

In my application you can navigate through several Activities until the Activity stack is quite deep.

We’d like a button on every Activity that will take you straight back to the main menu – i.e. pop all Activities from the stack except the first one.

I’ve put the button in a View that I can easily put on every Activity in the application, but I can’t figure out how to close several Activities in one fell swoop.

(If possible, it would be good if the View could work out how many Activities to close by itself – i.e. detect how deep on the stack its own Activity is.)

Answer 1

Have a look at the intent flag FLAG_ACTIVITY_CLEAR_TOP which says it brings the targeted activity to the top of the stack, removing everything else that might have been above it. So use that button you can add to all your activities to launch an intent which targets your main menu, with that flag set.

From the documentation:

If set, and 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.

For example, consider a task
consisting of the activities: A, B, C,
D. If D calls startActivity() with an
Intent that resolves to the component
of activity B, then C and D will be
finished and B receive the given
Intent, resulting in the stack now
being: A, B.

The currently running instance of
activity B in the above example will
either receive the new intent you are
starting here in its onNewIntent()
method, or be itself finished and
restarted with the new intent. If it
has declared its launch mode to be
“multiple” (the default) and you have
not set FLAG_ACTIVITY_SINGLE_TOP in
the same intent, then it will be
finished and re-created; for all other
launch modes or if
FLAG_ACTIVITY_SINGLE_TOP is set then
this Intent will be delivered to the
current instance’s onNewIntent().

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.