初步优化项目结构

lib/widget_system/widgets/StatefulWidget/DropdownButton/node1_base.dart

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+import 'package:flutter/material.dart';
+
+/// create by 张风捷特烈 on 2020-03-16
+/// contact me by email 1981462002@qq.com
+/// 说明:
+
+//    {
+//      "widgetId": 55,
+//      "name": 'DropdownButton基本用法',
+//      "priority": 1,
+//      "subtitle":
+//      "【value】 : 当前值   【T】\n"
+//      "【items】 : 下拉选框   【List<DropdownMenuItem<T>>】\n"
+//          "【icon】 : 图标   【Widget】\n"
+//          "【elevation】 : 影深   【double】\n"
+//          "【onChanged】 : 选择条目事件   【Function(T)】\n"
+//          "【backgroundColor】 : 背景色   【Color】",
+//    }
+class CustomDropDownButton extends StatefulWidget {
+  @override
+  _CustomDropDownButtonState createState() => _CustomDropDownButtonState();
+}
+
+class _CustomDropDownButtonState extends State<CustomDropDownButton> {
+  Color _color = Colors.red;
+  final _colors = [Colors.red, Colors.yellow, Colors.blue, Colors.green];
+  final _info = ["红色", "黄色", "蓝色", "绿色"];
+
+  @override
+  Widget build(BuildContext context) {
+    return Wrap(
+      children: <Widget>[
+        Container(
+          margin: EdgeInsets.symmetric(horizontal: 20),
+          width: 50,
+          height: 50,
+          color: _color,
+        ),
+        DropdownButton<Color>(
+            value: _color,
+            elevation: 1,
+            icon: Icon(
+              Icons.expand_more,
+              size: 20,
+              color: _color,
+            ),
+            items: _buildItems(),
+            onChanged: (v) => setState(() => _color = v??Colors.blue)),
+      ],
+    );
+  }
+
+  List<DropdownMenuItem<Color>> _buildItems() => _colors
+      .map((e) => DropdownMenuItem<Color>(
+          value: e,
+          child: Text(
+            _info[_colors.indexOf(e)],
+            style: TextStyle(color: e),
+          )))
+      .toList();
+}

lib/widget_system/widgets/StatefulWidget/DropdownButton/node2_style.dart

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+import 'package:flutter/material.dart';
+
+/// create by 张风捷特烈 on 2020-03-16
+/// contact me by email 1981462002@qq.com
+/// 说明:
+//    {
+//      "widgetId": 55,
+//      "name": 'DropdownButton的样式指定',
+//      "priority": 2,
+//      "subtitle":
+//      "【isDense】 : 是否紧排   【bool】\n"
+//      "【iconSize】 : 图标大小   【double】\n"
+//      "【hint】 : 提示组件   【Widget】\n"
+//          "【iconEnabledColor】 : 图标颜色   【Color】",
+//    }
+
+class StyleDropDownButton extends StatefulWidget {
+  @override
+  _StyleDropDownButtonState createState() => _StyleDropDownButtonState();
+}
+
+class _StyleDropDownButtonState extends State<StyleDropDownButton> {
+  Color _color = Colors.red ;
+  final List<Color> _colors = [Colors.red, Colors.yellow, Colors.blue, Colors.green];
+  final List<String> _info = ["红色", "黄色", "蓝色", "绿色"];
+
+  @override
+  Widget build(BuildContext context) {
+    return Wrap(
+      crossAxisAlignment: WrapCrossAlignment.center,
+      children: <Widget>[
+        Container(
+          margin: EdgeInsets.symmetric(horizontal: 20),
+          width: 50,
+          height: 50,
+          color: _color,
+        ),
+        DropdownButton<Color>(
+            hint: Text('请选择'),
+            isDense: true,
+            iconSize:20,
+            iconEnabledColor:_color,
+            value: _color,
+            items: _buildItems(),
+            onChanged: (v) => setState(() => _color = v??Colors.blue)),
+      ],
+    );
+  }
+
+  List<DropdownMenuItem<Color>> _buildItems() => _colors
+      .map((e) => DropdownMenuItem<Color>(
+          value: e,
+          child: Text(
+            _info[_colors.indexOf(e)],
+            style: TextStyle(color: e),
+          )))
+      .toList();
+}