Detect android app foreground and background state with LifecycleObserver

App.java

import android.app.Application;
import android.util.Log;
import android.arch.lifecycle.*;

public class App extends Application implements LifecycleObserver {

    @Override
    public void onCreate() {
        super.onCreate();
        ProcessLifecycleOwner.get().getLifecycle().addObserver(this);
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_STOP)
    void onAppBackgrounded() {
        Log.d("AppLog", "App in background");
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_START)
    void onAppForegrounded() {
        Log.d("AppLog", "App in foreground");
    }
}