Workmanager internal

Implementing a Foreground and Background Handler First, lets create our interface that will be implemented by a custom Application class. Something as simple as this: interface LifecycleDelegate { fun onAppBackgrounded() fun onAppForegrounded() }

we could use onTrimMemory and the TRIM_MEMORY_UI_HIDDEN flag to detect background events. So lets do that now. Add this into the onTrimMemory method callback body if (level == ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN) { // lifecycleDelegate instance was passed in on the constructor lifecycleDelegate.onAppBackgrounded() } So now we have the background event covered lets handle the foreground event. To do this we are going to use the onActivityResumed. This method gets called every time any Activity in your app is resumed, so this could be called multiple times if you have multiple Activities. What we will do is use a flag to mark it as resumed so subsequent calls are ignored, and then reset the flag when the the app is backgrounded. Lets do that now.

If you are using the Android Architecture Components library you can use the ProcessLifecycleOwner to set up a listener to the whole application process for onStart and onStop events. To do this, make your application class implement the LifecycleObserver interface and add some annotations for onStop and onStart to your foreground and background methods. Like so: