Application Foreground/Backgroud 상태 확인하기

Application이 Foreground인지, Background 상태인지 ActivityLifecycleCallbacks 를 사용하여 확인해본다.

enum class ApplicationState {
    FOREGROUND,
    BACKGROUND
}

class ApplicationLifecycleStatus : Application.ActivityLifecycleCallbacks {
    companion object {
        var state:ApplicationState = ApplicationState.FOREGROUND
    }

    override fun onActivityStarted(activity: Activity) {
        state = ApplicationState.FOREGROUND
    }

    override fun onActivityStopped(activity: Activity) {
        state = ApplicationState.BACKGROUND
    }

    override fun onActivityCreated(activity: Activity, savedInstanceState: Bundle?) { }

    override fun onActivityResumed(activity: Activity) { }

    override fun onActivityPaused(activity: Activity) { }

    override fun onActivitySaveInstanceState(activity: Activity, outState: Bundle) { }

    override fun onActivityDestroyed(activity: Activity) { }
}

ApplicationLifecycleStatus란 클래스는 Application.ActivityLifecycleCallbacks(https://developer.android.com/reference/kotlin/android/app/Application.ActivityLifecycleCallbacks)란 interface를 사용하여 구현을 한다.

구현한 ApplicationLifecycleStatus를 Application()을 상속받은 새로운 클래스에서 Callback으로 등록하여 준다.

class MainApplication : Application() {
    override fun onCreate() {
        super.onCreate()
        registerActivityLifecycleCallbacks(ApplicationLifecycleStatus())
    }
}