Prevent duplicate activities

Question

So, I'm both new to Java and to creating android apps, but not new to programming. I've read through most of the developer.android.com site, but I haven't been able to find this:

I want to make sure that a certain activity isn't running more than once at the same time. So we have a task somewhat like this:
Activity A) a TabActivity, which launches
Activity B) a ListView that, on-click, opens up
Activity C) which is the interface for a mediaplayer object

Right now, whenever somebody presses the back-button whilst in C (Which is a likely thing, because they're going to listen to a streaming 1-hour long mp3) and then presses another list item, instead of returning to C, C is opened a second time, and two streams are playing. Of course, I'd want only one instance of C running, and I want a second click on the list item to bring C back to the front. This could also be useful for notification intents.

I've been messing around with the flags (especially FLAG_ACTIVITY_NEW_TASK, FLAG_ACTIVITY_CLEAR_TOP and FLAG_ACTIVITY_REORDER_TO_FRONT), but no success so far.

If someone could help me out here I could focus on my next challenge - making it a real feed reader :P

Thanks in advance,

Answer 1

You need to flag your actvity as either "singleTask" or "singleInstance" in your manifest. I can't remember the exact differences between the 2, but either should do what you want. SingleInstance just does something different with the stack.

Example :

<activity android:name="MainActivity" android:launchMode="singleInstance"></activity>

You can handle new calls to startActivity() from the same activity instance with onNewIntent()

Answer 2

I've got it!

For those reading this question and wanting to know the summary: I mistakenly thought more then one activity was running, but it appeared more MediaPlayer instances where running. I made my mediaplayer a class member and am now controlling it from the onStart() event.

I am using SharedPreferences to check if the stream needs to reset and change source, or continue running and just show the interface.

Thanks for all your reactions. Really helped me out.