A task that will execute once,at some point within the specified window. If one of cancelTask(String, Class) or cancelAllTasks(Class) is called before this executes it will be cancelled. Note that you can request a one-off task to be executed at any point in the future, but to prevent abuse the scheduler will only set an alarm at a minimum of 30 seconds in the future. Your task can still be run earlier than this if some network event occurs to wake up the scheduler.