Android: detect if app enters a background

Question

It seems like tones of answers on this question but all incomplete. A have an app with multiple activities. All I need is an IF statement meaning that IF my app entered a background I do this ... and if it entered foreground I do this ...

!!! Keep in mind that if I'm switching from one activity to another meaning that my first activity stops, that doesn't mean that my app entered background - it's just one activity's replaced with another one.

Answer 1

First add some of the following necessary dependencies in app level gradle

dependencies {
def lifecycle_version = "2.1.0"

// ViewModel and LiveData
implementation "androidx.lifecycle:lifecycle-extensions:$lifecycle_version"
// alternatively - just ViewModel
implementation "androidx.lifecycle:lifecycle-viewmodel:$lifecycle_version" // For Kotlin use lifecycle-viewmodel-ktx
// alternatively - just LiveData
implementation "androidx.lifecycle:lifecycle-livedata:$lifecycle_version"
// alternatively - Lifecycles only (no ViewModel or LiveData). Some UI
//     AndroidX libraries use this lightweight import for Lifecycle
implementation "androidx.lifecycle:lifecycle-runtime:$lifecycle_version"

annotationProcessor "androidx.lifecycle:lifecycle-compiler:$lifecycle_version" // For Kotlin use kapt instead of annotationProcessor
// alternately - if using Java8, use the following instead of lifecycle-compiler
implementation "androidx.lifecycle:lifecycle-common-java8:$lifecycle_version"

// optional - ReactiveStreams support for LiveData
implementation "androidx.lifecycle:lifecycle-reactivestreams:$lifecycle_version" // For Kotlin use lifecycle-reactivestreams-ktx

// optional - Test helpers for LiveData
testImplementation "androidx.arch.core:core-testing:$lifecycle_version"

}

You may refer to the latest version of dependency here

https://developer.android.com/jetpack/androidx/releases/lifecycle?authuser=1

Your app must extend the Application class and override the following the methods given in example below.

You can simply achieve the same functionality using lifecycle-aware component of arch libraries. I have just posted one sample code for Kotlin and Java for your use case.

The Java version.

public class YourApp extends Application implements LifecycleObserver {

@Override
public void onCreate() {
    super.onCreate();

    ProcessLifecycleOwner.get().getLifecycle().addObserver(this);
}

// Application level lifecycle events
@OnLifecycleEvent(Lifecycle.Event.ON_START)
public void onEnteredForeground() {
    //Timber.d("Application did enter foreground");

}

@OnLifecycleEvent(Lifecycle.Event.ON_STOP)
public void onEnteredBackground() {
   // Timber.d("Application did enter background");
}

}

Kotlin version:

class ZumeApp : Application(), LifecycleObserver {

override fun onCreate() {
    super.onCreate()
    ProcessLifecycleOwner.get().lifecycle.addObserver(this)
}

// Application level lifecycle events
@OnLifecycleEvent(Lifecycle.Event.ON_START)
fun onEnteredForeground() {
    Timber.d("Application did enter foreground")

}

@OnLifecycleEvent(Lifecycle.Event.ON_STOP)
fun onEnteredBackground() {
    Timber.d("Application did enter background")
}
}

I hope it will help you. Leave a comment if it does not work or refer to the following article in android docs.

https://developer.android.com/topic/libraries/architecture/lifecycle?authuser=1