Working with the AppBar

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The top app bar provides a consistent place along the top of your app window for displaying information and actions from the current screen.

Ownership of the app bar varies depending on the needs of your app. When using fragments, the app bar can be implemented as an ActionBar that is owned by the host activity or a toolbar within your fragment's layout.

If all your screens use the same app bar that's always at the top and spans the width of the screen, use a theme-provided action bar hosted by the activity. Using theme app bars helps to maintain a consistent look and provides a place to host option menus and an Up button.

Use a toolbar hosted by the fragment if you want more control over the size, placement, and animation of the app bar across multiple screens. For example, you might need a collapsing app bar or one that spans only half the width of the screen and is vertically centered.

Different situations require different approaches for things like inflating menus and responding to user interaction. Understanding the different approaches and employing the best one for your app saves you time and helps ensure that your app functions properly.

The examples in this topic reference an ExampleFragment that contains an editable profile. The fragment inflates the following XML-defined menu in its app bar:

<!-- sample_menu.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_settings"
        android:icon="@drawable/ic_settings"
        android:title="@string/settings"
        app:showAsAction="ifRoom"/>
    <item
        android:id="@+id/action_done"
        android:icon="@drawable/ic_done"
        android:title="@string/done"
        app:showAsAction="ifRoom|withText"/>

</menu>

The menu contains two options: one for navigating to a profile screen and one to save any profile changes made.

Activity-owned app bar

The app bar is most commonly owned by the host activity. When the app bar is owned by an activity, fragments can interact with the app bar by overriding framework methods that are called during fragment creation.

Register with activity

You must inform the system that your app bar fragment is participating in the population of the options menu. To do this, call setHasOptionsMenu(true) in your fragment's onCreate(Bundle) method, as shown in the following example:

class ExampleFragment : Fragment() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setHasOptionsMenu(true)
    }
}

public class ExampleFragment extends Fragment {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setHasOptionsMenu(true);
    }
}

setHasOptionsMenu(true) tells the system that your fragment wants to receive menu-related callbacks. When a menu-related event occurs, like a click, the event-handling method is first called on the activity before being called on the fragment.

However, don't rely on this order in your application logic. If the same activity hosts multiple fragments, each fragment can supply menu options, in which case the callback order depends on the order in which the fragments are added.

Inflate the menu

To merge your menu into the app bar's options menu, override onCreateOptionsMenu() in your fragment. This method receives the current app bar menu and a MenuInflater as parameters. Use the menu inflater to create an instance of your fragment's menu, and then merge it into the current menu, as shown in the following example:

class ExampleFragment : Fragment() {
    ...
    override fun onCreateOptionsMenu(menu: Menu, inflater: MenuInflater) {
        inflater.inflate(R.menu.sample_menu, menu)
    }
}

public class ExampleFragment extends Fragment {
    ...
    @Override
    public void onCreateOptionsMenu(@NonNull Menu menu, @NonNull MenuInflater inflater) {
       inflater.inflate(R.menu.sample_menu, menu);
    }
}

Figure 2 shows the updated menu.

Handle click events

Every activity and fragment that participates in the options menu can respond to touches. The fragment's onOptionsItemSelected() receives the selected menu item as a parameter and returns a boolean to indicate whether the touch is consumed. Once an activity or fragment returns true from onOptionsItemSelected(), no other participating fragments receive the callback.

In your implementation of onOptionsItemSelected(), use a switch statement on the itemId of the menu item. If the selected item is yours, handle the touch appropriately and return true to indicate that the click event is handled. If the selected item isn't yours, call the super implementation. By default, the super implementation returns false to let menu processing continue.

class ExampleFragment : Fragment() {
    ...
    override fun onOptionsItemSelected(item: MenuItem): Boolean {
        return when (item.itemId) {
            R.id.action_settings -> {
                // Navigate to settings screen.
                true
            }
            R.id.action_done -> {
                // Save profile changes.
                true
            }
            else -> super.onOptionsItemSelected(item)
        }
    }
}

public class ExampleFragment extends Fragment {
    ...
    @Override
    public boolean onOptionsItemSelected(@NonNull MenuItem item) {
        switch (item.getItemId()) {
            case R.id.action_settings:  {
                // Navigate to settings screen.
                return true;
            }
            case R.id.action_done: {
                // Save profile changes.
                return true;
            }
            default:
                return super.onOptionsItemSelected(item);
        }

    }

}

Dynamically modify the menu

Place the logic to hide or show a button or change the icon in onPrepareOptionsMenu(). This method is called right before the menu is shown.

Continuing with the previous example, the Save button should be invisible until the user begins editing, and it should disappear after the user saves. Adding this logic to onPrepareOptionsMenu() makes the menu present correctly:

class ExampleFragment : Fragment() {
    ...
    override fun onPrepareOptionsMenu(menu: Menu){
        super.onPrepareOptionsMenu(menu)
        val item = menu.findItem(R.id.action_done)
        item.isVisible = isEditing
    }
}

public class ExampleFragment extends Fragment {
    ...
    @Override
    public void onPrepareOptionsMenu(@NonNull Menu menu) {
        super.onPrepareOptionsMenu(menu);
        MenuItem item = menu.findItem(R.id.action_done);
        item.setVisible(isEditing);
    }
}

When you need to update the menu, such as when a user presses the Edit button to edit the profile info, call invalidateOptionsMenu() on the host activity to request that the system call onCreateOptionsMenu(). After invalidation, you can make the updates in onCreateOptionsMenu(). Once the menu inflates, the system calls onPrepareOptionsMenu() and updates the menu to reflect the fragment's current state.

class ExampleFragment : Fragment() {
    ...
    fun updateOptionsMenu() {
        isEditing = !isEditing
        requireActivity().invalidateOptionsMenu()
    }
}

public class ExampleFragment extends Fragment {
    ...
    public void updateOptionsMenu() {
        isEditing = !isEditing;
        requireActivity().invalidateOptionsMenu();
    }
}

Fragment-owned app bar

If most screens in your app don't need an app bar, or if one screen needs a different app bar than the others, you can add a Toolbar to your fragment layout. Though you can add a Toolbar anywhere within your fragment's view hierarchy, you generally keep it at the top of the screen. To use the Toolbar in your fragment, provide an ID and obtain a reference to it in your fragment, as with any other view. You can also consider animating the toolbar using CoordinatorLayout behaviors.

<androidx.appcompat.widget.Toolbar
    android:id="@+id/myToolbar"
    ... />

When using a fragment-owned app bar, Google recommends using the Toolbar APIs directly. Do not use setSupportActionBar() and the Fragment menu APIs, which are appropriate only for activity-owned app bars.

Inflate the menu

The Toolbar convenience method inflateMenu(int) takes the ID of a menu resource as a parameter. To inflate an XML menu resource into your toolbar, pass the resId to this method, as shown in the following example:

class ExampleFragment : Fragment() {
    ...
    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        ...
        viewBinding.myToolbar.inflateMenu(R.menu.sample_menu)
    }
}

public class ExampleFragment extends Fragment {
    ...
    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        ...
        viewBinding.myToolbar.inflateMenu(R.menu.sample_menu);
    }

}

To inflate another XML menu resource, call the method again with the resId of the new menu. The new menu items are added to the menu, and the existing menu items are not modified or removed.

If you want to replace the existing menu set, clear the menu before calling inflateMenu(int) with the new menu ID, as shown in the following example:

class ExampleFragment : Fragment() {
    ...
    fun clearToolbarMenu() {
        viewBinding.myToolbar.menu.clear()
    }
}

public class ExampleFragment extends Fragment {
    ...
    public void clearToolbarMenu() {

        viewBinding.myToolbar.getMenu().clear()

    }

}

Handle click events

You can pass an OnMenuItemClickListener directly to the toolbar using the setOnMenuItemClickListener() method. This listener is invoked when the user selects a menu item from the action buttons presented at the end of the toolbar or the associated overflow. The selected MenuItem is passed to the listener's onMenuItemClick() method and can be used to consume the action, as shown in the following example:

class ExampleFragment : Fragment() {
    ...
    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        ...
        viewBinding.myToolbar.setOnMenuItemClickListener {
            when (it.itemId) {
                R.id.action_settings -> {
                    // Navigate to settings screen.
                    true
                }
                R.id.action_done -> {
                    // Save profile changes.
                    true
                }
                else -> false
            }
        }
    }
}

public class ExampleFragment extends Fragment {
    ...
    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        ...
        viewBinding.myToolbar.setOnMenuItemClickListener(item -> {
            switch (item.getItemId()) {
                case R.id.action_settings:
                    // Navigate to settings screen.
                    return true;
                case R.id.action_done:
                    // Save profile changes.
                    return true;
                default:
                    return false;
            }
        });
    }
}

Dynamically modify the menu

When your fragment owns the app bar, you can modify the Toolbar at runtime exactly like any other view.

Continuing with the previous example, the Save menu option should be invisible until the user begins editing, and it should disappear again when tapped:

class ExampleFragment : Fragment() {
    ...
    fun updateToolbar() {
        isEditing = !isEditing

        val saveItem = viewBinding.myToolbar.menu.findItem(R.id.action_done)
        saveItem.isVisible = isEditing

    }
}

public class ExampleFragment extends Fragment {
    ...
    public void updateToolbar() {
        isEditing = !isEditing;

        MenuItem saveItem = viewBinding.myToolbar.getMenu().findItem(R.id.action_done);
        saveItem.setVisible(isEditing);
    }

}

Add a navigation icon

If present, the navigation button appears at the start of the toolbar. Setting a navigation icon on the toolbar makes it visible. You can also set a navigation-specific onClickListener() that is called whenever the user clicks on the navigation button, as shown in the following example:

class ExampleFragment : Fragment() {
    ...
    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        ...
        myToolbar.setNavigationIcon(R.drawable.ic_back)

        myToolbar.setNavigationOnClickListener { view ->
            // Navigate somewhere.
        }
    }
}

public class ExampleFragment extends Fragment {
    ...
    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        ...
        viewBinding.myToolbar.setNavigationIcon(R.drawable.ic_back);
        viewBinding.myToolbar.setNavigationOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                // Navigate somewhere.
            }
        });
    }
}