Kotlin: Start an activity from a thread - kotlin

Question

I try to program an kids-launcher.
I search for my problem three days but I do not find a solution (I am a beginner in android/kotlin)
I want to start an app and after a while (when the time for the kids is elapsed) I want to come back to my launcher
I wrote the function
fun openApp(context: Context, packageName: String?) {
context.startActivity(context.packageManager.getLaunchIntentForPackage(packageName!!))
}
I started an app and after a while (when the time for the kids is elapsed) I want to come back to my launcher
openApp(this, packageName)
timer.schedule(10000) {
openApp(this, "PackageNameMyLauncher")
}
But it does not work.
when I write "openApp(applicationContext, packageName)" instead, than it works a little bit. But when the app is closed and I press the home button than it won´t work.
I think I didn´t understand some fundamental at the moment.
In the thread there is no context
I also tried to run a pendingIntent with an alarmManager
val intent = Intent(this, MainActivity::class.java)
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_SINGLE_TOP)
val mPendingIntent = PendingIntent.getActivity(
this,
123456, //PendingIntentId,
intent,
PendingIntent.FLAG_CANCEL_CURRENT
)
val mgr = this.getSystemService(Context.ALARM_SERVICE) as AlarmManager
mgr.set(AlarmManager.RTC, System.currentTimeMillis() + 1000, mPendingIntent)
System.exit(0) //finish()
but that is also not working

Answer 1

I know it is not an answer, but when I was a beginner what I lacked was some kind of upper-level design ideas
I don't think Android provides the ability to schedule app opening without user's intention. And also your timer will be destroyed when you will remove application from processes.
I think your best bet will be to design app that way, that it will be unavailable till some time will elapse. You can save the last timestamp when the app became unavailable on the backend or in shared preferences and later on you can compare it with current timestamp, which you will get each time you open the app. If the
currentTimeStamp - savedTimeStamp >= timeLimit you will make further logic of your app available, otherwise you will display some kind of a message.