title: How to use rx java's interval for background task
body: <p>According to <a href="https://github.com/ReactiveX/RxAndroid/issues/257#issuecomment-164263215" rel="nofollow">https://github.com/ReactiveX/RxAndroid/issues/257#issuecomment-164263215</a> . interval is just for active code, and if app is not wake up, it will not work. So how to use interval for background scheduling tasks?</p>