Add:创建 flutter go web 版

lib/widgets/elements/Form/Button/PopupMenuButton/demo.dart

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+/// Created with Android Studio.
+/// User: 一晟
+/// Date: 2018/11/22
+/// Time: 上午12:03
+/// email: zhu.yan@alibaba-inc.com
+/// target: PopupMenuButton 的示例
+
+import 'package:flutter_web/material.dart';
+
+// RaisedButton 默认按钮的实例
+// isDisabled:是否是禁用，isDisabled 默认为true
+enum WhyFarther { harder, smarter, selfStarter, tradingCharter }
+
+class PopupMenuButtonDefault extends StatelessWidget {
+  final bool isDisabled;
+  final String type;
+
+  const PopupMenuButtonDefault(
+      [ this.type = 'default1',  this.isDisabled = true])
+      : assert(isDisabled != null),
+        super();
+
+  @override
+  Widget build(BuildContext context) {
+    switch (type) {
+      case 'default1':
+        return default1(context);
+        break;
+      case 'default2':
+        return default2(context);
+        break;
+      case 'default3':
+        return default3(context);
+        break;
+      default:
+        return default1(context);
+    }
+  }
+
+  Widget default1(BuildContext context) {
+    return PopupMenuButton<WhyFarther>(
+      onSelected: (WhyFarther result) {
+        // setState(() { _selection = result; });
+      },
+      itemBuilder: (BuildContext context) => <PopupMenuEntry<WhyFarther>>[
+            const PopupMenuItem<WhyFarther>(
+              value: WhyFarther.harder,
+              child: Text('Working a lot harder'),
+            ),
+            const PopupMenuItem<WhyFarther>(
+              value: WhyFarther.smarter,
+              child: Text('Being a lot smarter'),
+            ),
+            const PopupMenuItem<WhyFarther>(
+              value: WhyFarther.selfStarter,
+              child: Text('Being a self-starter'),
+            ),
+            const PopupMenuItem<WhyFarther>(
+              value: WhyFarther.tradingCharter,
+              child: Text('Placed in charge of trading charter'),
+            ),
+          ],
+    );
+  }
+
+  Widget default2(BuildContext context) {
+    return PopupMenuButton(
+        child: Text('点我试试'),
+        onSelected: (String value) {},
+        itemBuilder: (BuildContext context) => <PopupMenuItem<String>>[
+               PopupMenuItem(value: "选项一的内容", child:  Text("选项一")),
+               PopupMenuItem(value: "选项二的内容", child:  Text("选项二"))
+            ]);
+  }
+
+  Widget default3(BuildContext context) {
+    return PopupMenuButton(
+        //child: Text('点我试试'),// child 和 icon 不能同时用
+        icon: Icon(Icons.menu),
+        onSelected: (String value) {},
+        itemBuilder: (BuildContext context) => <PopupMenuItem<String>>[
+               PopupMenuItem(value: "选项一的内容", child:  Text("选项一")),
+               PopupMenuItem(value: "选项二的内容", child:  Text("选项二"))
+            ]);
+  }
+}
+
+
+class PopupMenuButtonCustom extends StatelessWidget {
+  final widget;
+  final parent;
+  const PopupMenuButtonCustom([this.widget,this.parent])
+      : super();
+  @override
+  Widget build(BuildContext context) {
+    final String selectStr = widget.options['defaultSelect'];
+    return PopupMenuButton(
+        //如果提供，则用于此按钮的widget。
+        child: RaisedButton.icon(
+          disabledColor:Colors.red,
+          icon: Icon(Icons.message, size: 25.0,color:Colors.yellow),
+          label: Text(
+                '自定义按钮', style: TextStyle(color: Colors.white),
+                semanticsLabel: 'FLAT BUTTON'),
+          onPressed:(){} // 激活状态按钮
+        ),
+        // 打开时放置菜单的z坐标。这可以控制菜单下方阴影的大小。
+        elevation:10.0,
+        // 如果提供，则用于此按钮的图标。
+        //icon
+        // 菜单项的值（如果有），在菜单打开时应突出显示。
+        //initialValue:options['defaultSelect'],
+        initialValue:selectStr,
+        // 按下按钮时调用以创建要在菜单中显示的项目。
+        itemBuilder: (BuildContext context) => <PopupMenuItem<String>>[
+           PopupMenuItem(value: "选项一的内容", child:  Text("选项一")),
+           PopupMenuItem(value: "选项二的内容", child:  Text("选项二")),
+           PopupMenuItem(value: "选项三的内容", child:  Text("选项三")),
+           PopupMenuItem(value: "选项四的内容", child:  Text("选项四"))
+        ],
+        // 应用于弹出菜单按钮的偏移量(x,y)。
+        offset:Offset(0.0,50.0),
+        // 当用户在不选择项目的情况下关闭弹出菜单时调用。
+        onCanceled:()=>
+          print('onCanceled'),
+        // 当用户从此按钮创建的弹出菜单中选择一个值时调用。
+        onSelected:(String value){
+          print('onSelected:${parent.setState}');
+          parent.setState((){
+            widget.options['defaultSelect']= value;
+          });
+        },
+        // 默认情况下匹配IconButton的8 dps填充。在某些情况下，特别是在此按钮作为列表项的尾随元素出现的情况下，能够将填充设置为零是有用的。
+        padding: EdgeInsets.only(bottom: 20.0, top: 20.0, left: 0.0, right: 0.0),
+        //描述按下按钮时将发生的操作的文本。
+        tooltip:'这是信息'
+    );
+  }
+}