片段的OnDestroyView永不称为按“后退”按钮

Question

In a basic application based on fragments navigation, fragment B replaces fragment A. Then I press the back button to return to fragment A and I would hope that OnDestroyView of fragment B would be called but it is never called. I use AddToBackStack() in the transaction. Is it normal?

I use AppCompat 26.0 and Xamarin Android.

UPDATE :

It can be easily replicated with any Xamarin example. For example https://developer.xamarin.com/samples/monodroid/FragmentsWalkthrough/

In DetailsFragment.cs, add the following:

    public override void OnDestroyView()
    {
        base.OnDestroyView();
    }

Then if you add a breakpoint at OnDestroyView, you will see that it is never called even when you press the Back button. In other words, each time I add a fragment, a new instance is created, but never destroyed.

Answer 1

As seen in Fragment Lifecycle a fragment which is part of the backstack is usually kept in stopped state and not destroyed . onDestroyView() is part of the destroy phase and will not be called if the fragment is merely stopped .

So yes, that is normal. Try to use onStop() instead.

Answer 2

After 2 days, finally I have found the problem. It seems a Xamarin bug. I have changed the Target from Android 8.0 to Android 7.1. I compiled it and it worked fine. Then I changed back to 8.0 again and it started to work fine too.

I could replicate this solution with the Xamarin examples too.