Add:创建 flutter go web 版

lib/widgets/elements/Frame/Box/ConstrainedBox/index.dart

@@ -0,0 +1,70 @@
+/// Author: xiaojia.dxj
+/// Date: 2019-01-08 15:56:53 
+/// Last Modified by:   xiaojia.dxj
+/// Last Modified time: 2019-01-08 15:56:53 
+/// email: xiaojia.dxj@alibaba-inc.com
+
+import 'package:flutter_web/material.dart';
+
+import 'package:flutter_go/components/widget_demo.dart';
+import 'demo.dart';
+
+const String _Text = '''
+### **简介**
+> 添加额外的限制条件到child上
+- 比如说，你限制child最小高度为50.0像素，就可以用constraints: const BoxConstraints(minHeight：50）
+
+''';
+const String _Text1 = '''
+### **基本用法**
+> 添加额外的限制条件到child上
+- ex:添加ConstrainedBox约束如下，传入不同Width约束的Container效果
+minWidth: 100.0,
+minHeight: 20.0,
+maxWidth: 300.0,
+maxHeight: 50.0
+
+''';
+
+class Demo extends StatefulWidget {
+  static const String routeName = '/element/Frame/Box/ConstrainedBox';
+
+  _DemoState createState() => _DemoState();
+}
+
+class _DemoState extends State<Demo> {
+  @override
+  Widget build(BuildContext context) {
+    return WidgetDemo(
+      title: 'ConstrainedBox',
+      codeUrl: 'elements/Frame/Box/ConstrainedBox/demo.dart',
+      contentList: [
+        _Text,
+        _Text1,
+        // maxWidth: 300.0,
+        ConstrainedBoxCreate(currWidth: 500, describe: "currWidth>maxWidth"),
+        SizedBox(
+          height: 10.0,
+        ),
+        ConstrainedBoxCreate(currWidth: 300, describe: "currWidth=maxWidth"),
+        SizedBox(
+          height: 10.0,
+        ),
+        ConstrainedBoxCreate(currWidth: 200, describe: "currWidth<maxWidth"),
+        SizedBox(
+          height: 10.0,
+        ),
+
+        // minWidth: 100.0,
+        ConstrainedBoxCreate(currWidth: 150, describe: "currWidth>minWidth"),
+        SizedBox(
+          height: 10.0,
+        ),
+        ConstrainedBoxCreate(currWidth: 100, describe: "currWidth=minWidth"),
+
+      ],
+      docUrl:
+          'https://docs.flutter.io/flutter/widgets/ConstrainedBox-class.html',
+    );
+  }
+}