PopupMenuButton 菜单按钮

弹出菜单栏，可指定偏移、颜色、影深、形状等属性。接收item选中的事件和取消选择事件。

相关按钮

PopupMenuDivider

PopupMenuButton基本使用

   <br />【itemBuilder】 : 构造器   【PopupMenuItemBuilder<T>】<br />【offset】 : 偏移   【Offset】<br />【color】 : 背景颜色   【Color】<br />【shape】 : 形状   【ShapeBorder】<br />【elevation】 : 影深   【double】<br />【onCanceled】 : 取消事件   【Function()】<br />【onSelected】 : 选择事件   【Function(T)】<br />![96.gif](https://cdn.nlark.com/yuque/0/2020/gif/326147/1589446520178-d3c1a938-2d9d-4bd2-ac98-e66f8a85940e.gif#align=left&display=inline&height=310&margin=%5Bobject%20Object%5D&name=96.gif&originHeight=310&originWidth=404&size=240825&status=done&style=none&width=404)

import 'package:flutter/material.dart';
import '../../../dialogs/dialog_about.dart';
class CustomPopupMenuButton extends StatefulWidget {
  @override
  _CustomPopupMenuButtonState createState() => _CustomPopupMenuButtonState();
}

class _CustomPopupMenuButtonState extends State<CustomPopupMenuButton> {
  final map = {
    "关于": Icons.info_outline,
    "帮助": Icons.help_outline,
    "问题反馈": Icons.add_comment,
  };

  @override
  Widget build(BuildContext context) {
    return PopupMenuButton<String>(
      itemBuilder: (context) => buildItems(),
      offset: Offset(0, 50),
      color: Color(0xffF4FFFA),
      elevation: 1,
      shape: RoundedRectangleBorder(
          borderRadius: BorderRadius.only(
        topLeft: Radius.circular(20),
        bottomRight: Radius.circular(20),
        topRight: Radius.circular(5),
        bottomLeft: Radius.circular(5),
      )),
      onSelected: (e) {
        print(e);
        if (e == '关于') {
          DialogAbout.show(context);
        }
      },
      onCanceled: () => print('onCanceled'),
    );
  }

  List<PopupMenuItem<String>> buildItems() {
    return map.keys
        .toList()
        .map((e) => PopupMenuItem<String>(
            value: e,
            child: Wrap(
              spacing: 10,
              children: <Widget>[
                Icon(
                  map[e],
                  color: Colors.blue,
                ),
                Text(e),
              ],
            )))
        .toList();
  }
}