对话框，通常是应用的一些信息当然我们一般都是需要自定义的，不用flutter自带的

动画icons

自带的就下面14中动画图片，也就是从一种状态变换成另外一种状态
比如 AnimatedIcons.close_menu,这个表示从close(X)的样式变成menu(三)的样式

var icons = [
      AnimatedIcons.add_event,
      AnimatedIcons.arrow_menu,
      AnimatedIcons.close_menu,
      AnimatedIcons.ellipsis_search,
      AnimatedIcons.event_add,
      AnimatedIcons.home_menu,
      AnimatedIcons.list_view,
      AnimatedIcons.menu_arrow,
      AnimatedIcons.menu_close,
      AnimatedIcons.menu_home,
      AnimatedIcons.pause_play,
      AnimatedIcons.play_pause,
      AnimatedIcons.search_ellipsis,
      AnimatedIcons.view_list
    ];

animationController = AnimationController(
      vsync: this,
      duration: Duration(microseconds: 2000),
    );

    animationController.forward(); //加上这个，动画才能执行，可以放到按钮的点击事件里面去，
...
 AnimatedIcon(
                      size: 30,
                      icon: icons[i],
                      progress: animationController,
                      semanticLabel: 'Show menu',
                    ),