ExpandedControllerActivity

 // cast_expanded_controller_menu.xml
 <menu xmlns:android="//schemas.android.com/apk/res/android"
       xmlns:app="//schemas.android.com/apk/res-auto" >
     <item
     android:id="@+id/media_route_menu_item"
     app:actionProviderClass="androidx.mediarouter.app.MediaRouteActionProvider"
     app:showAsAction="always" />
 </menu>
 

 // MyExpandedControllerActivity.java
 class MyExpandedControllerActivity extends ExpandedControllerActivity {
     @Override
     public boolean onCreateOptionsMenu(Menu menu) {
         super.onCreateOptionsMenu(menu);
         getMenuInflater().inflate(R.menu.cast_expanded_controller_menu, menu);
         CastButtonFactory.setUpMediaRouteButton(this, menu, R.id.media_route_menu_item);
         return true;
     }
 }
 

 // my_styles.xml
 <style name="Theme.CastVideosTheme" parent="Theme.AppCompat.Light.NoActionBar">
     <item name="castExpandedControllerToolbarStyle">
         @style/ThemeOverlay.AppCompat.Dark.ActionBar
     </item>
 </style>
 

 // arrays.xml
 <array name="cast_expanded_controller_control_buttons">
     <item>@id/cast_button_type_empty</item>
     <item>@id/cast_button_type_rewind_30_seconds</item>
     <item>@id/cast_button_type_forward_30_seconds</item>
     <item>@id/cast_button_type_empty</item>
 </array>
 ...
 // styles.xml
 <style name="Theme.MyTheme">
     <item name="castExpandedControllerStyle">
         @style/CustomCastExpandedController
     </item>
 </style>
 ...
 <style name="CustomCastExpandedController" parent="CastExpandedController">
     <item name="castControlButtons">
         @array/cast_expanded_controller_control_buttons
     </item>
 </style>
 

 // arrays.xml
 <array name="cast_expanded_controller_control_buttons">
     <item>@id/cast_button_type_empty</item>
     <item>@id/cast_button_type_rewind_30_seconds</item>
     <item>@id/cast_button_type_custom</item>
     <item>@id/cast_button_type_empty</item>
 </array>

 // MyCustomUIController.java
 class MyCustomUIController extends UIController {
     private final View mButton;

     public MyCustomUIController(View button) {
         mButton = button;
         // Set the drawable and onClickListener on the button.
         ...
     }

     @Override
     public onMediaStatusUpdated() {
         // Update the state of mButton based on the latest the media status.
         ...
         mButton.setVisible(false);
         ...
     }
 }

 // MyExpandedControllerActivity.java
 class MyExpandedControllerActivity extends ExpandedControllerActivity {
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         ImageView customButtonView = getButtonImageViewAt(2);
         MyCustomUIController myCustomUiController = new MyCustomUIController(customButtonView);
         getUIMediaController().bindViewToUIController(customButtonView, myCustomUiController);
         ...
     }
 }