Android Popup通话功能

Question

请原谅我，但我只是android编程的初学者！我想制作一个弹出菜单，点击一个项目后我想调用die public void function RefreshMenuItems（2）;但没有任何反应。我希望有人可以告诉我如何从主要活动中调用函数

这是我的代码：

/**
 * A Button that acts as the view element for the popup menu.
 */
final Button btn = (Button) findViewById(R.id.btn_click);
/**
 * Step 1: Create a new instance of popup menu
 */
final PopupMenu popupMenu = new PopupMenu(this, btn);
/**
 * Step 2: Inflate the menu resource. Here the menu resource is
 * defined in the res/menu project folder
 */
popupMenu.inflate(R.menu.popup_menu);
/**
 * Step 3: Call show() method on the popup menu to display the
 * menu when the button is clicked.
 */
btn.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        popupMenu.show();
    }
});
/**
 *  Handle menu item clicks
 */
popupMenu.setOnMenuItemClickListener(
    new PopupMenu.OnMenuItemClickListener() {
        @Override
        public boolean onMenuItemClick(MenuItem item) {
            switch (item.getItemId()) {
            case R.id.menu_red:
                // Here i want to call the function but nothing happens ??
                RefreshMenuItems(2);
                return true;
            case R.id.menu_blue:
                btn.setBackgroundColor(0xfff00000);
                break;
            case R.id.menu_green:
                btn.setBackgroundColor(0xfff00000);
                 break;
            }
            return true; 
        }
    }
);