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;
}
}