didChangeAppLifecycleState method
Called when the system puts the app in the background or returns the app to the foreground.
An example of implementing this method is provided in the class-level documentation for the WidgetsBindingObserver class.
This method exposes notifications from SystemChannels.lifecycle.
See also:
- AppLifecycleListener, an alternative API for responding to application lifecycle changes.
Implementation
@mustCallSuper
@override
void didChangeAppLifecycleState(AppLifecycleState state) {
  switch (state) {
    case AppLifecycleState.resumed:
      onResumed();
      break;
    case AppLifecycleState.inactive:
      onInactive();
      break;
    case AppLifecycleState.paused:
      onPaused();
      break;
    case AppLifecycleState.detached:
      onDetached();
      break;
  }
}