Android fragment navigation without button click

Issue

I am using a "Drawer Navigation" project using fragments and so far this method works:

button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Navigation.findNavController(view).navigate(R.id.nav_gallery);
        }
    });

But I want to use the navigation method inside a fragment class calling a function like this:

boolean b;
public void fragmentNavigation() {
    if (b) {
        Navigation.findNavController(getView()).navigate(R.id.nav_gallery);
    } 
}

I am a newbie using the navigation architecture and I still don't know if I need to declare some type of action listener for that function or how to make it work.

Solution

You can do that, but be careful of :

1. using getView() is Nullable; so you must make sure that your fragment has already created the view.

You can solve this by a couple of ways

First: Overriding onViewCreated() which has a nonNull view argument

@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    fragmentNavigation(view);

}
boolean b;
public void fragmentNavigation(View view) {
    if (b) {
        Navigation.findNavController(view).navigate(R.id.nav_gallery);
    } 
}

Second: Create a View field in the fragment class, and set it within onCreateView()

View view;
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container,
                         @Nullable Bundle savedInstanceState) {
    view = inflater.inflate(R.layout.main_fragment, container, false);
    return view;
}

then always call fragmentNavigation(view); on that view field.

2. Your fragment is hosted by the NavHostFragment of the Navigation Graph; so that you can avoid potential IllegalStateException

Answered By - Zain