Question

Is there a way to vizualise the activity stack, at some moment during debug, or normal run ?

Answer 1

You can get some useful information with the activity manager.

ActivityManager         manager = (ActivityManager)getApplication().getSystemService( Activity.ACTIVITY_SERVICE );

This will show you the top, bottom and size of the stack, and description may be useful. You will have to search the running tasks to find the current activity.

RunningTaskInfo         task = manager.getRunningTasks( 10 ).get( 0 );
task.baseActivity();
task.numActivities();
task.topActivity();
task.description();

This has a pkgLst method that may be helpful.

RunningAppProcessInfo   app = manager.getRunningAppProcesses().get( 0 );
app.pkgList();

Not as useful or straightforward as you were hoping for, but it might help.

Activity provides the getCallingActivity() method that you could add to logs in onPause and onResume as suggested before.

There is also if ( isChild() ) getParent(); for embedded activities.