Padding组件
在 html 中常见的布局标签都有 padding 属性，但是 Flutter 中很多 Widget 是没有 padding 属性。这个时候我们可以用 Padding 组件处理容器与子元素直接的间距。
该组件接收两个属性：
- padding ：padding 值, EdgeInsetss 设置填充的值
- child ：子组件
例如，要实现前面的网格布局里面的单元格之间的间距，就可以使用Padding组件。
import ‘package:flutter/material.dart‘;
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
// TODO: implement build
return MaterialApp(
home: Scaffold(
appBar: AppBar(title: Text(‘FlutterDemo‘)),
body: LayoutDemo(),
));
}
}
class LayoutDemo extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Padding(
padding: EdgeInsets.fromLTRB(0, 0, 10, 0),
child: GridView.count(
crossAxisCount: 2,
childAspectRatio: 1.7,
children: <Widget>[
Padding(
padding: EdgeInsets.fromLTRB(10, 10, 0, 0),
child: Image.network(‘https://www.itying.com/images/flutter/1.png‘,
fit: BoxFit.cover),
),
Padding(
padding: EdgeInsets.fromLTRB(10, 10, 0, 0),
child: Image.network(‘https://www.itying.com/images/flutter/2.png‘,
fit: BoxFit.cover),
),
Padding(
padding: EdgeInsets.fromLTRB(10, 10, 0, 0),
child: Image.network(‘https://www.itying.com/images/flutter/3.png‘,
fit: BoxFit.cover),
),
Padding(
padding: EdgeInsets.fromLTRB(10, 10, 0, 0),
child: Image.network(‘https://www.itying.com/images/flutter/4.png‘,
fit: BoxFit.cover),
),
Padding(
padding: EdgeInsets.fromLTRB(10, 10, 0, 0),
child: Image.network(‘https://www.itying.com/images/flutter/5.png‘,
fit: BoxFit.cover),
),
Padding(
padding: EdgeInsets.fromLTRB(10, 10, 0, 0),
child: Image.network(‘https://www.itying.com/images/flutter/6.png‘,
fit: BoxFit.cover),
),
],
));
}
}
Row 水平布局组件
Row组件用于实现水平布局，相比于ListView的水平排列而言，这个Row的宽度是可控的，二者之间的参数也是不一样的，Row组件技术的参数为：
- mainAxisAlignment ：主轴的排序方式
- crossAxisAlignment：次轴的排序方式
- children：组件子元素
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(
height: 800.0,
width: 400.0,
color: Colors.pink,
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
IconContainer(Icons.search,color: Colors.blue),
IconContainer(Icons.home,color: Colors.orange),
IconContainer(Icons.select_all,color: Colors.red),
],
),
);
}
}
class IconContainer extends StatelessWidget{
double size=32.0;
Color color=Colors.red;
IconData icon;
IconContainer(this.icon,{this.color,this.size});
@override
Widget build(BuildContext context) {
// TODO: implement build
return Container(
height: 100.0,
width: 100.0,
color: this.color,
child: Center(
child: Icon(this.icon,size: this.size,color: Colors.white)
),
);
}
}
Column 垂直布局组件
Column组件是区别于Row组件的，用于实现垂直布局，接收的参数和上面的Row是一样的。
class LayoutDemo extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Container(
height: 800.0,
width: 400.0,
color: Colors.pink,
child: Column(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
crossAxisAlignment: CrossAxisAlignment.end,
children: <Widget>[
IconContainer(Icons.search,color: Colors.blue),
IconContainer(Icons.home,color: Colors.orange),
IconContainer(Icons.select_all,color: Colors.red),
],
),
);
}
}
Expanded组件
Expanded 可以用在 Row 和 Column 布局中 ，用于实现类似web中的Flex布局。
import ‘package:flutter/material.dart‘;
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
// TODO: implement build
return MaterialApp(
home: Scaffold(
appBar: AppBar(title: Text(‘FlutterDemo‘)),
body: LayoutDemo(),
));
}
}
class LayoutDemo extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Row(
children: <Widget>[
Expanded(
flex: 1,
child: IconContainer(Icons.search,color: Colors.blue)
),
Expanded(
flex: 2,
child: IconContainer(Icons.home,color: Colors.orange),
),
Expanded(
flex: 1,
child: IconContainer(Icons.select_all,color: Colors.red),
),
],
);
}
}
class IconContainer extends StatelessWidget{
double size=32.0;
Color color=Colors.red;
IconData icon;
IconContainer(this.icon,{this.color,this.size});
@override
Widget build(BuildContext context) {
// TODO: implement build
return Container(
height: 100.0,
width: 100.0,
color: this.color,
child: Center(
child: Icon(this.icon,size: this.size,color: Colors.white)
),
);
}
}
上面是实现等分的，既然是类似于Flex的，那么，也可以实现部分固定宽度，剩余部分自适应的效果：
class LayoutDemo extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Row(
children: <Widget>[
Expanded(
flex: 1,
child: IconContainer(Icons.home,color: Colors.orange),
),
IconContainer(Icons.search,color: Colors.blue)
],
);
}
}
最后，我们就可以结合上面的知识，实现下面的布局了：
import ‘package:flutter/material.dart‘;
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
// TODO: implement build
return MaterialApp(
home: Scaffold(
appBar: AppBar(title: Text(‘FlutterDemo‘)),
body: LayoutDemo(),
));
}
}
class LayoutDemo extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Column(
children: <Widget>[
Row(
children: <Widget>[
Expanded(
child: Container(
height: 180,
color: Colors.black,
child: Text(‘你好Flutter‘),
),
)
],
),
SizedBox(height: 10),
Row(
children: <Widget>[
Expanded(
flex: 2,
child: Container(
height: 180,
child: Image.network("https://ss3.bdstatic.com/70cFv8Sh_Q1YnxGkpoWK1HF6hhy/it/u=2606512668,2361120991&fm=27&gp=0.jpg",fit: BoxFit.cover),
)
),
SizedBox(width: 10),
Expanded(
flex: 1,
child: Container(
height: 180,
child: ListView(
children: <Widget>[
Container(
height: 85,
child: Image.network("https://ss3.bdstatic.com/70cFv8Sh_Q1YnxGkpoWK1HF6hhy/it/u=2606512668,2361120991&fm=27&gp=0.jpg",fit: BoxFit.cover),
),
SizedBox(height: 10),
Container(
height: 85,
child: Image.network("https://ss0.bdstatic.com/70cFuHSh_Q1YnxGkpoWK1HF6hhy/it/u=2191520521,2689315141&fm=27&gp=0.jpg",fit: BoxFit.cover),
)
],
)
)
),
],
)
],
);
}
}
原文地址：https://www.cnblogs.com/yuyujuan/p/10970016.html
时间： 2024-10-12 04:19:28