You have to understand how activity life cycle works. Please read android manual. You can't call onPause/onResume an activity directly
onPause : Called when the system is about to start resuming a previous activity. This is typically used to commit unsaved changes to persistent data, stop animations and other things that may be consuming CPU, etc.
onResume : Called when the activity will start interacting with the user.
Please read http://developer.android.com/reference/android/app/Activity.html