How to prevent multiple instances of an Activity when it is launched with different Intents

Question

I've come across a bug in my application when it is launched using the "Open" button on the Google Play Store app (previously called Android Market). It seems that launching it from the Play Store uses a different Intent than launching it from the phone's application menu of icons. This is leading to multiple copies of the same Activity being launched, which are conflicting with each other.

For example, if my app consists of the Activities A-B-C, then this issue can lead to a stack of A-B-C-A.

I tried using android:launchMode="singleTask" on all the Activities to fix this problem, but it has the unwanted side-effect of clearing the Activity stack to root, whenever I hit the HOME button.

The expected behavior is: A-B-C -> HOME -> And when the app is restored, I need: A-B-C -> HOME -> A-B-C

Is there a good way to prevent launching multiple Activities of the same type, without resetting to the root activity when using the HOME button?

Answer 1

Add this to onCreate and you should be good to go:

// Possible work around for market launches. See https://issuetracker.google.com/issues/36907463
// for more details. Essentially, the market launches the main activity on top of other activities.
// we never want this to happen. Instead, we check if we are the root and if not, we finish.
if (!isTaskRoot()) {
    final Intent intent = getIntent();
    if (intent.hasCategory(Intent.CATEGORY_LAUNCHER) && Intent.ACTION_MAIN.equals(intent.getAction())) {
        Log.w(LOG_TAG, "Main Activity is not the root.  Finishing Main Activity instead of launching.");
        finish();
        return;       
    }
}