Como detectar se a aplicação está minimizada ou não (How to detect Android application in background or foreground events)

LifecycleObserver.kt

/**
Doc: https://developer.android.com/reference/android/arch/lifecycle/ProcessLifecycleOwner
belongs to Maven artifact "android.arch.lifecycle:extensions:1.1.1" (include in your dependences)
*/
class MyApplication : Application(), LifecycleObserver {

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

    @OnLifecycleEvent(Lifecycle.Event.ON_STOP)
    fun onAppBackgrounded() {
        Log.d(LOG, "App in background")
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_START)
    fun onAppForegrounded() {
        Log.d(LOG, "App in foreground")
    }
}