Android 9 API 28 FLAG_ACTIVITY_NEW_TASK, is it really enforced?

Question

According to new behavior documented here https://developer.android.com/about/versions/pie/android-9.0-changes-all#fant-required starting activities from non-activity context requires FLAG_ACTIVITY_NEW_TASK flag, perhaps...

So I have created sandbox app that can launch activity of another apps by package name and activity name. The core function used to launching, looks like this:

fun Context.startActivity(packageName: String, activityName: String) {
    applicationContext.startActivity(Intent(Intent.ACTION_MAIN).apply {
        component = ComponentName(packageName, activityName)
    })
}

What is odd, by calling this function I can succesfully start any exported activity without passing FLAG_ACTIVITY_NEW_TASK. It is quite different from what google saying about that. Or maybe I wrongly understand this new behavior requirements?

Off course I tested this on API 28 but also on lower API's.

Can someone explain in which cases this new behavior can breaks any feature that works on older APIs?

Answer 1

As per this change it seems to be a restriction when FLAG_ACTIVITY_NEW_TASK is not set while launching an activity from a non-activity context.

StartActivity method in Activity.java is overriden and avoid this restriction.