How to set title in app bar with Navigation Architecture Component

It's actually because of:

android:label="fragment_main"

Which you have set in the xml.

So what is the proper way to show the title for Fragments using Navigation Component?

setTitle() works at this point. But, because you set label for those Fragments, it might show the label again when recreating the Activity. The solution will probably be deleting android:label and then do your things with code:

((AppCompatActivity) getActivity()).getSupportActionBar().setTitle("your title");

Or:

((AppCompatActivity) getActivity()).getSupportActionBar().setSubtitle("your subtitle");

In onCreateView().

---

Found a workaround:

interface TempToolbarTitleListener {
    fun updateTitle(title: String)
}

class MainActivity : AppCompatActivity(), TempToolbarTitleListener {

    ...

    override fun updateTitle(title: String) {
        binding.toolbar.title = title
    }
}

Then:

(activity as TempToolbarTitleListener).updateTitle("custom title")

Check this out too:Dynamic ActionBar title from a Fragment using AndroidX Navigation

As others are still participating in answering this question, let me answer my own question as APIs has changed since then.

First, remove android:label from the fragment/s that you wish to change the title of, from within navigation.xml (aka Navigation Graph),.

Now you can change the title from with the Fragment by calling

(requireActivity() as MainActivity).title = "My title"

But the preferred way you should be using is the API NavController.addOnDestinationChangedListener from within MainActivity. An Example:

NavController.OnDestinationChangedListener { controller, destination, arguments ->
// compare destination id
    title = when (destination.id) {
        R.id.someFragment -> "My title"
        else -> "Default title"
    }

//    if (destination == R.id.someFragment) {
//        title = "My title"
//    } else {
//        title = "Default Title"        
//    }
}

You can use this code in your fragment if you don't specify your app bar(default appbar)

(activity as MainActivity).supportActionBar?.title = "Your Custom Title"

Remember to delete the android:label attribute in your navigation graph

Happy code ^-^