Android 9 Development Cookbook - Third Edition

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What if we wanted the Download option to stand out when it's available? We could tell Android we want the menu in the action bar by adding the following code to onPrepareOptionsMenu() (before the return statement):

menuItem.setShowAsAction(MenuItem.SHOW_AS_ACTION_ALWAYS); 

Now if you run the code, you will see the Download menu item in the action bar, but the behavior isn't correct.

Earlier, when we didn't have a menu item in the action bar, Android called onPrepareOptionsMenu() each time we opened the overflow menu so the visibility was always updated. To correct this behavior, add the following line of code to the toggleMenu() method:

invalidateOptionsMenu(); 

The invalidateOptionsMenu() call tells Android that our option ...