介绍
什么是Container?
这个跟Android中的ViewGroup很像,主要是做布局约束控制的,不太一样的地方Container只能有一只子控件
能力如下:
- margin 设置Container距离外边容器的边距
- padding 设置Container内部子空间和自己的边距
- witdh 设置宽度大小
- height 设置高度大小
- color 设置背景颜色
- child 设置子空间
- alignment 指的对其的方式,这个是指Container中子空间(child)的对其方式,不是指Container自己的对其方式
- decoration 通过这个属性可以Container 设置边框、弧度、图片等
效果展示
创建Container
import 'package:flutter/material.dart';
void main() => runApp(MaterialApp(
title: "Container Title",
home: Scaffold(
appBar: AppBar(
title: Text(
"Container Titlte",
style: TextStyle(color: Colors.cyan),
),
),
body: Container(
color: Colors.yellow,
width: 400,
height: 400,
child: Text("Hello Container"),
),
),
));
设置边距
void main() => runApp(MaterialApp(
title: "Container Title",
home: Scaffold(
appBar: AppBar(
title: Text(
"Container Titlte",
style: TextStyle(color: Colors.cyan),
),
),
body: Container(
margin: EdgeInsets.all(20),
padding: EdgeInsets.symmetric(horizontal: 100),
color: Colors.yellow,
width: 400,
height: 400,
child: Text("Hello Container"),
),
),
));
margin 上下左右设置20,padding设置子view 左边距离父view 100
设置对齐方式
void main() => runApp(MaterialApp(
title: "Container Title",
home: Scaffold(
appBar: AppBar(
title: Text(
"Container Titlte",
style: TextStyle(color: Colors.cyan),
),
),
body: Container(
alignment: Alignment.bottomRight,
margin: EdgeInsets.all(20),
padding: EdgeInsets.symmetric(horizontal: 100),
color: Colors.yellow,
width: 400,
height: 400,
child: Text("Hello Container",style: TextStyle(fontSize: 15,color: Colors.deepOrange),),
),
),
));
发现问题是在右下方,并且距离右边还有点距离,这个就是alignment起的作用,并且padding也收到alignment的影响所以才会距离右边有点距离
边框设置
边框设置主要是用到了decoration来来构建
void main() => runApp(MaterialApp(
title: "Container Title",
home: Scaffold(
appBar: AppBar(
title: Text(
"Container Titlte",
style: TextStyle(color: Colors.cyan),
),
),
body: Container(
decoration: BoxDecoration(
//设置填充颜色
color: Colors.blue,
//设置边框大小和颜色
border: Border.all(color: Colors.deepOrangeAccent,width: 20)
),
alignment: Alignment.bottomRight,
margin: EdgeInsets.all(20),
padding: EdgeInsets.symmetric(horizontal: 100),
color: Colors.yellow,
width: 400,
height: 400,
child: Text("Hello Container",style: TextStyle(fontSize: 15,color: Colors.deepOrange),),
),
),
))
直接运行会包错误的
Failed assertion: line 266 pos 15: 'color == null || decoration == null': Cannot provide both a color and a decoration
什么意思呢?就是color和decoration不能同时设置,我们修改一下代码,把color注释掉
void main() => runApp(MaterialApp(
title: "Container Title",
home: Scaffold(
appBar: AppBar(
title: Text(
"Container Titlte",
style: TextStyle(color: Colors.cyan),
),
),
body: Container(
decoration: BoxDecoration(
//设置填充颜色
color: Colors.blue,
//设置边框大小和颜色
border: Border.all(color: Colors.deepOrangeAccent,width: 20)
),
alignment: Alignment.bottomRight,
margin: EdgeInsets.all(20),
padding: EdgeInsets.symmetric(horizontal: 100),
// color: Colors.yellow,
width: 400,
height: 400,
child: Text("Hello Container",style: TextStyle(fontSize: 15,color: Colors.deepOrange),),
),
),
));
会发现有了一个橘红色的边框,内部填充区域是蓝色
如果加个圆角怎么弄呢?
import 'package:flutter/material.dart';
void main() => runApp(MaterialApp(
title: "Container Title",
home: Scaffold(
appBar: AppBar(
title: Text(
"Container Titlte",
style: TextStyle(color: Colors.cyan),
),
),
body: Container(
decoration: BoxDecoration(
//设置填充颜色
color: Colors.blue,
//设置10弧度的圆角
borderRadius: BorderRadius.all(Radius.circular(10)),
//设置边框大小和颜色
border: Border.all(color: Colors.deepOrangeAccent,width: 20)
),
alignment: Alignment.bottomRight,
margin: EdgeInsets.all(20),
padding: EdgeInsets.symmetric(horizontal: 100),
// color: Colors.yellow,
width: 400,
height: 400,
child: Text("Hello Container",style: TextStyle(fontSize: 15,color: Colors.deepOrange),),
),
),
));
发现边框出现了弧度,现在decoration 有点像Android 中的Shape
设置阴影和渐变
import 'package:flutter/material.dart';
void main() => runApp(MaterialApp(
title: "Container Title",
home: Scaffold(
appBar: AppBar(
title: Text(
"Container Titlte",
style: TextStyle(color: Colors.cyan),
),
),
body: Container(
decoration: BoxDecoration(
//设置填充颜色
color: Colors.blue,
//设置10弧度的圆角
borderRadius: BorderRadius.all(Radius.circular(10)),
//设置阴影
boxShadow: <BoxShadow>[
BoxShadow(
color: Colors.green,
blurRadius: 1.0,
spreadRadius: 1.0,
offset: Offset(-1.0, 1.0),
),
],
//设置渐变
gradient: LinearGradient(colors: [Colors.cyan, Colors.black]),
//设置边框大小和颜色
border: Border.all(color: Colors.deepOrangeAccent, width: 20)),
alignment: Alignment.bottomRight,
margin: EdgeInsets.all(20),
padding: EdgeInsets.symmetric(horizontal: 100),
// color: Colors.yellow,
width: 400,
height: 400,
child: Text(
"Hello Container",
style: TextStyle(fontSize: 15, color: Colors.deepOrange),
),
),
),
));
设置渐变后,填充color的颜色蓝色被渐变的颜色给覆盖了,边框外边多了绿颜色的一个阴影效果
设置图片
void main() => runApp(MaterialApp(
title: "Container Title",
home: Scaffold(
appBar: AppBar(
title: Text(
"Container Titlte",
style: TextStyle(color: Colors.cyan),
),
),
body: Container(
decoration: BoxDecoration(
//设置填充颜色
color: Colors.blue,
//设置10弧度的圆角
borderRadius: BorderRadius.all(Radius.circular(10)),
//设置阴影
boxShadow: <BoxShadow>[
BoxShadow(
color: Colors.green,
blurRadius: 1.0,
spreadRadius: 1.0,
offset: Offset(-1.0, 1.0),
),
],
//设置渐变
gradient: LinearGradient(colors: [Colors.cyan, Colors.black]),
//给背景设置图片
image: DecorationImage(
image: NetworkImage(
"http://img5.duitang.com/uploads/item/201206/15/20120615031447_R5EcS.jpeg")),
//设置边框大小和颜色
border: Border.all(color: Colors.deepOrangeAccent, width: 20)),
alignment: Alignment.bottomRight,
margin: EdgeInsets.all(20),
padding: EdgeInsets.symmetric(horizontal: 100),
// color: Colors.yellow,
width: 400,
height: 400,
child: Text(
"Hello Container",
style: TextStyle(fontSize: 15, color: Colors.deepOrange),
),
),
),
));
发现渐变和图片进行了叠加,图片显示在最上方
设置前景色
void main() => runApp(MaterialApp(
title: "Container Title",
home: Scaffold(
appBar: AppBar(
title: Text(
"Container Titlte",
style: TextStyle(color: Colors.cyan),
),
),
body: Container(
decoration: BoxDecoration(
//设置填充颜色
color: Colors.blue,
//设置10弧度的圆角
borderRadius: BorderRadius.all(Radius.circular(10)),
//设置阴影
boxShadow: <BoxShadow>[
BoxShadow(
color: Colors.green,
blurRadius: 1.0,
spreadRadius: 1.0,
offset: Offset(-1.0, 1.0),
),
],
//设置渐变
gradient: LinearGradient(colors: [Colors.cyan, Colors.black]),
//给背景设置图片
image: DecorationImage(
image: NetworkImage(
"http://img5.duitang.com/uploads/item/201206/15/20120615031447_R5EcS.jpeg")),
//设置边框大小和颜色
border: Border.all(color: Colors.deepOrangeAccent, width: 20)),
alignment: Alignment.bottomRight,
margin: EdgeInsets.all(20),
padding: EdgeInsets.symmetric(horizontal: 100),
foregroundDecoration: BoxDecoration(
image: DecorationImage(
image: NetworkImage(
'http://www.pptbz.com/pptpic/UploadFiles_6909/201203/2012031220134655.jpg'),
centerSlice: Rect.fromLTRB(270.0, 180.0, 1360.0, 730.0),
),
),
// color: Colors.yellow,
width: 400,
height: 400,
child: Text(
"Hello Container",
style: TextStyle(fontSize: 15, color: Colors.deepOrange),
),
),
),
));
发现一旦设置了前景色,所有的内容都被遮挡住了
约束限制
void main() => runApp(MaterialApp(
title: "Container Title",
home: Scaffold(
appBar: AppBar(
title: Text(
"Container Titlte",
style: TextStyle(color: Colors.cyan),
),
),
body: Container(
//设置最大宽高为200
constraints: BoxConstraints(maxHeight: 200, maxWidth: 200),
decoration: BoxDecoration(
//设置填充颜色
color: Colors.blue,
//设置10弧度的圆角
borderRadius: BorderRadius.all(Radius.circular(10)),
//设置阴影
boxShadow: <BoxShadow>[
BoxShadow(
color: Colors.green,
blurRadius: 1.0,
spreadRadius: 1.0,
offset: Offset(-1.0, 1.0),
),
],
//设置渐变
gradient: LinearGradient(colors: [Colors.cyan, Colors.black]),
//给背景设置图片
image: DecorationImage(
image: NetworkImage(
"http://img5.duitang.com/uploads/item/201206/15/20120615031447_R5EcS.jpeg")),
//设置边框大小和颜色
border: Border.all(color: Colors.deepOrangeAccent, width: 20)),
alignment: Alignment.bottomRight,
margin: EdgeInsets.all(20),
padding: EdgeInsets.symmetric(horizontal: 100),
foregroundDecoration: BoxDecoration(
image: DecorationImage(
image: NetworkImage(
'http://www.pptbz.com/pptpic/UploadFiles_6909/201203/2012031220134655.jpg'),
centerSlice: Rect.fromLTRB(270.0, 180.0, 1360.0, 730.0),
),
),
// color: Colors.yellow,
width: 400,
height: 400,
child: Text(
"Hello Container",
style: TextStyle(fontSize: 15, color: Colors.deepOrange),
),
),
),
));
constraints 用来显示Container的宽高
发现布局变小了,因为我们指定的最大狂宽高是200