AlertDialog gets reshown on orientation change

Question

Code for question on Github
I have a app which is using fragments + viewmodels. In one fragment I need to present a list of options to the user when they hit a button. I'm doing this using an AlertDialog builder and it works to solve that problem. But if I open the application, hit the button to show the alertdialog, dismiss the dialog, and then rotate the phone to trigger a teardown/buildup the alertdialog get's reshown.

I'm using Android's databinding to bind ui stuff to the ViewModel(not sure if it matters). So the basic flow is:

• App starts
• Fragment subscribes to 1 observable in the ViewModel
• User clicks button
• Due to databinding the click is handled in the ViewModel by the method buttonClicked()
• Inside vm.buttonClicked() function I get data and update the observable the fragment is observing
• Fragment see's new data in observable
• Fragment creates AlertDialog in code and shows dialog to user
• User either makes a selection or dismisses the dialog
• User rotates phone, causes lifecycle change
• When the ui get's rebuilt, it shows the AlertDialog again

I have created a simple demo on github.

If you clone that repo then start the app but DONT hit the button, orientation changes go as expected. If you click the button and dismiss the dialog then rotate the phone, you'll see that the AlertDialog get's reshown.

Answer 1

If you are working with LiveData and events, this can help you to tackle some scenarios. In summary, you should work with SingleLiveEvents

Answer 2

ViewModel's lifecycle is different than of the fragment. When the orientation changes the Fragment gets recreated but the ViewModel stays.

Now what's happening is, when you update the value of the MutableLiveData it broadcasts an update to the Observer; when the Fragment is recreated on rotation change, it subscribes to the LiveData all over again and since there is an update on the value, the MutableLiveData broadcasts the update to the newly subscribed observer.

So you should, for example, save your fragment state in onSaveInstanceState, use the savedInstanceState to get the last update to the MutableLiveData value and check if a change had happened in the observer before showing the dialog.

Or you can move the dialog logic to the on click handler. Showing a dialog in an Observer is not a good approach in my opinion.