How to change MenuItem icon in ActionBar programmatically

You can't use findViewById() on menu items in onCreate() because the menu layout isn't inflated yet. You could create a global Menu variable and initialize it in the onCreateOptionsMenu() and then use it in your onClick().

private Menu menu;

In your onCreateOptionsMenu()

this.menu = menu;

In your button's onClick() method

menu.getItem(0).setIcon(ContextCompat.getDrawable(this, R.drawable.ic_launcher));

Lalith's answer is correct.

You may also try this approach:

button.setOnClickListener(new View.OnClickListener() {        @Override        public void onClick(View v) {            invalidateOptionsMenu();        }    }); @Override public boolean onPrepareOptionsMenu(Menu menu) {    MenuItem settingsItem = menu.findItem(R.id.action_settings);    // set your desired icon here based on a flag if you like    settingsItem.setIcon(ContextCompat.getDrawable(this, R.drawable.ic_launcher));     return super.onPrepareOptionsMenu(menu); }

This works for me. It should be in your onOptionsItemSelected(MenuItem item) method item.setIcon(R.drawable.your_icon);