Navigation with View Binding

Question

I'm trying to replace all findViewById using View Binding. But, I can't change my NavController code line using View Binding.

val navController = findNavController(this, R.id.mainHostFragment)

to

var binding : ActivityMainBinding
val navController = findNavController(this, binding.mainHostFragment)

How can I do that?

Answer 1

You can't replace it with View Binding. findNavController does more than finding the view in the layout.

Have a look at the source code here

/**
* Find a {@link NavController} given a local {@link Fragment}.
*
* <p>This method will locate the {@link NavController} associated with this Fragment,
* looking first for a {@link NavHostFragment} along the given Fragment's parent chain.
* If a {@link NavController} is not found, this method will look for one along this
* Fragment's {@link Fragment#getView() view hierarchy} as specified by
* {@link Navigation#findNavController(View)}.</p>
*
* @param fragment the locally scoped Fragment for navigation
* @return the locally scoped {@link NavController} for navigating from this {@link Fragment}
* @throws IllegalStateException if the given Fragment does not correspond with a
* {@link NavHost} or is not within a NavHost.
*/
@NonNull
public static NavController findNavController(@NonNull Fragment fragment) {
Fragment findFragment = fragment;
while (findFragment != null) {
    if (findFragment instanceof NavHostFragment) {
        return ((NavHostFragment) findFragment).getNavController();
    }
    Fragment primaryNavFragment = findFragment.getParentFragmentManager()
            .getPrimaryNavigationFragment();
    if (primaryNavFragment instanceof NavHostFragment) {
        return ((NavHostFragment) primaryNavFragment).getNavController();
    }
    findFragment = findFragment.getParentFragment();
}
// Try looking for one associated with the view instead, if applicable
View view = fragment.getView();
if (view != null) {
    return Navigation.findNavController(view);
}
throw new IllegalStateException("Fragment " + fragment
        + " does not have a NavController set");
}

It does more than just finding the controller. It traverses, creates fragment, creates views and throw an exception.

View binding just generates a binding class with all the views of your layout in it. It is not meant for finding the navigation controller of the app.