> When switching back and forth between activities, by default, they are not > destroyed and recreated - unless necessary.
This is irrelevant. Activities, by default, are destroyed when clearing the task. > If you are concerned with maintaining state (like a list view's scroll > position), you need to review the Activity Lifecycle. Although it is possible to maintain the state after finishing activities, that's not what I'm asking about. The idea is to clear the navigation stack, which is called the Task in Android, when navigating to certain Activities, without finishing other Activities. To keep the Task empty, the Activities are indeed destroyed by Android. What I want is to keep the Task empty without destroying the Activities. This is so that pressing BACK will exit the application on any of these "tab" activities, but that switching between the "tab" activities won't destroy and recreate them. In a purely theoretical sense, these "tab" activities would share the same position 0 in the stack. The TabActivity uses an ActivityGroup to accomplish this. What I want to know is if there is a way to flag either the Activity in the manifest, or the Intent which starts the Activity, to accomplish this. ... After giving this some thought, I think that this is not possible, and this is my theory on why. I theorize that Android internally keeps track of which Activities are open inside of a process with tasks: a process has a List<Task>. A Task correspondingly would have a Stack<Activity>. This is the only data collection which contains available Activities; otherwise the process would require two data collections to track: a List<Task> and a List<Activity>. Or, a Task would have a Stack<Activity> of Activities on the navigation stack and a List<Activity> of unfinished Activities not on the navigation stack. Having two data collections to track, while not impossible, would be slightly messier. If it is the case that the only data collection of Activities a process has is List<Task> and the Task correspondingly only has a Stack<Activity>, and if the OS cleared the task without finishing() the Activities, then it would have no reference to the non- finished Activities, so there would be no way for Android to find an Activity that is already instantiated and non-finished. Essentially, for this to work, a Task would have to have both a navigation stack of non-finished Activities Stack< Activity > and a list of unfinished Activities List<Activity> to support this framework. In any case, even if the above theory is incorrect, I can't find the equivalent of a CLEAR_NAVIGATION_STACK flag which doesn't finish the Activities in a Task. -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
