flutte页面布局四

AspectRatio 组件

AspectRatio 的作用是根据设置调整子元素 child 的宽高比。

AspectRatio 首先会在布局限制条件允许的范围内尽可能的扩展，widget 的高度是由宽度和比率

aspectRatio 

决定的，类似于 BoxFit 中的 contain，按照固定比率去尽量占满区域。如果在满足所有限制条件过后无法找到一个可行的尺寸，AspectRatio 最终将会去优先适应布局限制条件，而忽略所设置的比率。 

import 'package:flutter/material.dart';void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        home: Scaffold(
        appBar: AppBar(title: Text('FlutterDemo')),
        body: LayoutDemo(),
      ));
  }
}
class LayoutDemo extends StatelessWidget {
 @override
  Widget build(BuildContext context) {
    return Container(
       200,
      child: AspectRatio(
        aspectRatio: 2.0/1.0,
        child: Container(
          color: Colors.red,
        ),
      ),

    );
  }
}

在上面的例子中，给组件的父级设置了宽度200，然后设置该组件的宽高比为2:1，这样就得到了一个宽200，高100的容器，但是更多的时候，是用来做平铺的。

  

Card 组件 

Card 是卡片组件块，内容可以由大多数类型的 Widget 构成，Card 具有圆角和阴影，这让它看起来有立体感。该组件有三个常用的可选参数：

•  margin ：外边距
• child：子组件
• Shape ：Card 的阴影效果，默认的阴影效果为圆角的长方形边。

class LayoutDemo extends StatelessWidget {
 @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return ListView(
      children: <Widget>[
          Card(
            margin: EdgeInsets.all(10),
            child: Column(
              children: <Widget>[
                ListTile(
                  title:Text("张三",style: TextStyle(fontSize: 28)) ,
                  subtitle: Text("高级工程师"),
                ),
                ListTile(title:Text("电话：xxxxx") , ),
                ListTile(title:Text("地址：xxxxxx") ,)
              ],
            ),
          ),
          Card(
            margin: EdgeInsets.all(10),
            child: Column(
              children: <Widget>[
                ListTile(
                  title:Text("李四",style: TextStyle(fontSize: 28)) ,
                  subtitle: Text("高级工程师"),
                ),
                ListTile(title:Text("电话：xxxxx") , ),
                ListTile(title:Text("地址：xxxxxx") ,)
              ],
            ),
          ),
          Card(
            margin: EdgeInsets.all(10),
            child: Column(
              children: <Widget>[
                ListTile(
                  title:Text("王五",style: TextStyle(fontSize: 28)) ,
                  subtitle: Text("高级工程师"),
                ),
                ListTile(title:Text("电话：xxxxx") , ),
                ListTile(title:Text("地址：xxxxxx") ,)
              ],
            ),
          ),
      ],
    );
  }
}

card下的图文混排

class LayoutDemo extends StatelessWidget {
 @override
  Widget build(BuildContext context) {
    List listData=[
      {
          "title": 'Candy Shop',
          "author": 'Mohamed Chahin',
          "imageUrl": 'https://www.itying.com/images/flutter/1.png',
          "description": 'Flutter is Google’s mobile UI framework for crafting high-quality native experiences on iOS and Android in record time. Flutter works with existing',
      },
       {
          "title": 'Childhood in a picture',
          "author": 'Google',
          "imageUrl": 'https://www.itying.com/images/flutter/2.png',
          "description": 'Flutter is Google’s mobile UI framework for crafting high-quality native experiences on iOS and Android in record time. Flutter works with existing',
      },
  ];
    return ListView(
      children: listData.map((value){
        return Card(
          margin: EdgeInsets.all(10),
          child:Column(
              children: <Widget>[
                  AspectRatio(
                    aspectRatio: 20/9,
                    child: Image.network(value["imageUrl"],fit: BoxFit.cover,),
                  ),
                  ListTile(
                    leading: CircleAvatar(
                      backgroundImage:NetworkImage(value["imageUrl"])
                    ),
                    title: Text(value["title"]),
                    subtitle: Text(value["description"],maxLines: 1,overflow: TextOverflow.ellipsis),                    
                  )
              ],
          ),

        );

      }).toList(),
    );
  }
}