Using Toolbar with Fragments

Base on @Faisal Naseer answer. Here is the full example (with few notes) for using custom Toolbar with navigation and menu in Fragment

fragment_home.xml

<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"">

    ...
    <androidx.appcompat.widget.Toolbar
            android:id="@+id/toolbar_home"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            app:title="Home" /> 

</androidx.constraintlayout.widget.ConstraintLayout>

HomeFragment.kt

class HomeFragment : BaseFragment() {

    override fun onCreate(savedInstanceState: Bundle?) {
        // setHasOptionsMenu(true): don't need this anymore
    }

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        return inflater.inflate(R.layout.fragment_home, container, false)
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        toolbar_home.setNavigationIcon(R.drawable.ic_back) // need to set the icon here to have a navigation icon. You can simple create an vector image by "Vector Asset" and using here
        toolbar_home.setNavigationOnClickListener {
            // do something when click navigation
        }

        toolbar_home.inflateMenu(R.menu.menu_home)
        toolbar_home.setOnMenuItemClickListener {
            when (it.itemId) {
                R.id.action_add -> {
                    // do something
                    true
                }
                R.id.action_update -> {
                    // do something
                    true
                }
                else -> {
                    super.onOptionsItemSelected(it)
                }
            }
        }
    }
}

menu_home.xml

<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <item
        android:id="@+id/action_add"
        android:title="@string/add_device"
        app:showAsAction="never" />

    <item
        android:id="@+id/action_update_room"
        android:title="@string/update_room"
        app:showAsAction="never" />

</menu>

Hope it help

Fragments don't have such method setSupportActionBar(). ActionBar is a property of Activity, so to set your toolbar as the actionBar, your activity should extend from ActionBarActivity and then you can call in your Fragment:

 ((ActionBarActivity)getActivity()).setSupportActionBar(mToolbar);

UPDATE

If you're using AppCompatActivity :

 ((AppCompatActivity)getActivity()).setSupportActionBar(mToolbar);

I have seen a lot of answers mentioning to setSupportActionBar for toolbar inside Fragment but this approach may go wrong if you are having a a toolbar in Activity and a separate Toolbar in Fragment.

1. As you shift setSupportActionBar from Activity's Toolbar to Fragment's toolbar, You may face duplication of MenuItem even you try to override using setHasOptionsMenu(true).
2. Secondly If you want to update Activity's Toolbar you see your changes are not reflected because of setSupportActionBar inside your Fragment.

So in order to avoid this I recommend to use toolbar methods like this inside fragment to inflate menu and use

 toolbar = (Toolbar) view.findViewById(R.id.toolbar_frag);
    toolbar.inflateMenu(R.menu.frag_menu_items);
    Menu menu = toolbar.getMenu();

and use Toolbar.OnMenuItemClickListener interface to receive with menuItems click events.

Edit (Section Copied from MrEngineer13 answer)

and if you are worried about the back button you can set it like this

toolbar.setNavigationIcon(getResources().getDrawable(R.drawable.ic_action_back));
toolbar.setNavigationOnClickListener(new View.OnClickListener() {
   @Override
   public void onClick(View v) {
       //What to do on back clicked
   }
});