Flutter 超实用简单菜单弹出框 PopupMenuButton功能

相信在实际开发过程当中,肯定少不了这样的功能: 点击 AppBar 右上角的按钮,弹出一个菜单供用户选择。 幸运的是,Flutter 提供给我们了一个 Widget,直接就能实现如上的效果。 PopupMenuButton 还是老规矩,先看官方的说明: Displays a menu when pressed and calls onSelected [1] when the menu is dismissed because an item was selected. The value passed to onSelected [2] is the value of the sele