How to detect when an Android app goes to the background and come back to the foreground

Question

I am trying to write an app that does something specific when it is brought back to the foreground after some amount of time. Is there a way to detect when an app is sent to

Answer 1

The android.arch.lifecycle package provides classes and interfaces that let you build lifecycle-aware components

Your application should implement the LifecycleObserver interface:

public class MyApplication extends Application implements LifecycleObserver {

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

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

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

To do that, you need to add this dependency to your build.gradle file:

dependencies {
    implementation "android.arch.lifecycle:extensions:1.1.1"
}

As recommended by Google, you should minimize the code executed in the lifecycle methods of activities:

A common pattern is to implement the actions of the dependent components in the lifecycle methods of activities and fragments. However, this pattern leads to a poor organization of the code and to the proliferation of errors. By using lifecycle-aware components, you can move the code of dependent components out of the lifecycle methods and into the components themselves.

You can read more here: https://developer.android.com/topic/libraries/architecture/lifecycle