I'd like to know how properly handle system back button action using Navigation Controller. In my app I have two fragments (for ex. fragment1 and fragment2) and I have an action in fragment1 with destination to fragment2. Everything works well except one thing - when user presses system back button in fragment2 I want to show a dialog (using DialogFragment for example) to confirm exit. What is the best way to implement this behavior? If I use app:defaultNavHost="true" in my host fragment then it automatically goes back ignoring my rules. And, additionally, what is this component for?
Should I use "pop to" may be?
32 Answers
Newest Update - April 25th, 2019
New release androidx.activity ver. 1.0.0-alpha07 brings some changes
More explanations in android official guide: Provide custom back navigation
Example:
public class MyFragment extends Fragment {
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// This callback will only be called when MyFragment is at least Started.
OnBackPressedCallback callback = new OnBackPressedCallback(true /* enabled by default */) {
@Override
public void handleOnBackPressed() {
// Handle the back button event
}
};
requireActivity().getOnBackPressedDispatcher().addCallback(this, callback);
// The callback can be enabled or disabled here or in handleOnBackPressed()
}
...
}
