Flutter基础widgets教程-SizedOverflowBox篇

1 SizedOverflowBox

SizedOverflowBox主要的布局行为有两点：1 尺寸部分。通过将自身的固定尺寸，传递给child，来达到控制child尺寸的目的；undefined

2 超出部分。可以突破父节点尺寸的限制，超出部分也可以被渲染显示，与OverflowBox类似。

2 构造函数

       SizedOverflowBox({
           Key key,
           @required this.size,
           this.alignment = Alignment.center,
           Widget child,
       })
   
  

3 常用属性

3.1 size：固定的尺寸

size: Size(100.0, 200.0),
  

3.2 alignment：对齐方式

alignment:Alignment.topLeft,
  

3.2.1 顶部左边

alignment:Alignment.topLeft,
  

3.2.2 顶部中间

alignment:Alignment.topCenter,
  

3.2.3 顶部右边

alignment:Alignment.topRight,
  

3.2.4 中部左边

alignment:Alignment.centerLeft,
  

3.2.5 中部中间

alignment:Alignment.center,
  

3.2.6 中部右边

alignment:Alignment.centerRight,
  

3.2.7 底部左边

alignment:Alignment.bottomLeft,
  

3.2.8 底部中间

alignment:Alignment.bottomCenter,
  

3.2.9 底部右边

alignment:Alignment.bottomRight,
  

3.3 child：子控件

child: Text("内容"),
  

4.显示效果

5.代码

       import 'package:flutter/material.dart';
       import 'package:flutter/services.dart';
       import 'package:flutter_markdown/flutter_markdown.dart';
       // 字体适配
       import '../../utils/app_size.dart';
       class ListSizedOverflowBox extends StatelessWidget {
         @override
         Widget build(BuildContext context) {
          return DefaultTabController(
             length: 2,
             child: Scaffold(
               appBar: AppBar(
                 title: Text('SizedOverflowBox'),
                 backgroundColor: Color(0xFFfafcff),
                 bottom: TabBar(labelColor: Color(0xff030303), tabs: [
                   Tab(
                     text: "效果",
                   ),
                   Tab(
                     text: "属性",
                   )
                 ]),
               ),
               body: TabBarView(children: [
                 Container(
                     decoration: new BoxDecoration(
                       color: new Color(0xffffffff),
                       borderRadius: new BorderRadius.circular((AppSize.width(20))),
                     ),
                     child: ShowEffect()),
                 Container(
                     decoration: new BoxDecoration(
                       color: new Color(0xffffffff),
                       borderRadius: new BorderRadius.circular((AppSize.width(20))),
                     ),
                     child: ShowAttribute()),
               ]),
             ),
           );
         }
       }
       // 效果
       class ShowEffect extends StatelessWidget {
         @override
         Widget build(BuildContext context) {
          return MaterialApp(
             home: Scaffold(
               appBar: AppBar(
                 title: Text("SizedOverflowBox"),
               ),
               body: Container(
                 color: Colors.green,
                 alignment: Alignment.topRight,
                 width: 200.0,
                 height: 200.0,
                 padding: EdgeInsets.all(5.0),
                 child: SizedOverflowBox(
                   size: Size(100.0, 200.0),
                   child: Container(
                     color: Colors.red,
                     width: 200.0,
                     height: 100.0,
                   ),
                 ),
               ),
             ),
           );
         }
       }
       // 属性
       class ShowAttribute extends StatelessWidget {
         @override
         Widget build(BuildContext context) {
          return Container(
             child: FutureBuilder(
               future: rootBundle.loadString('lib/markdown/sizedOverflowBox.md'),
               builder: (BuildContext context, AsyncSnapshot snapshot) {
                if (snapshot.hasData) {
                  return Markdown(
                     data: snapshot.data,
                     selectable: true,
                   );
                 } else {
                  return Center(
                     child: Text("加载中..."),
                   );
                 }
               },
             ),
           );
         }
       }
   
  

   
  
  

此代码已共享到码云，已对60多种widget做演示及解释。一直更新中https://gitee.com/nmgwap/flutter_app