Flutter-BoxDecoration的使用说明
BoxDecoration通常用于给Widget组件设置边框效果、阴影效果、渐变色等效果；先来看下关于BoxDecoration的定义：
const BoxDecoration({
this.color,//设置背景的
this.image,//设置背景图片
this.border,//设置边框
this.borderRadius,//设置圆角效果
this.boxShadow,//设置阴影效果
this.gradient,//设置背景渐变效果
this.shape = BoxShape.rectangle,//设置是圆形还是方形
})
BoxDecoration的使用
接下来，将会使用一个Column对象，从上到下展示一组使用BoxDecoration属性的效果
1、boxShadow展示阴影效果
2、shape展示圆形效果，可能会有点变形，因为设置的Container的宽高不同导致
3、border: BorderDirectional绘制边框，top表示上，start表示左，end表示右，bottom表示下
4、border: Border绘制边框
注意：：存在image: DecorationImage的情况下，渐变色会被遮挡
5、gradient: SweepGradient绘制渐变色
6、gradient: RadialGradient绘制渐变色
7、gradient: LinearGradient绘制渐变色；并使用borderRadius: BorderRadius.all(Radius.circular (12.0))来为Container绘制圆角效果
根据上面的情况，编写代码：
import 'dart:math';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
class BoxDecorationDemo extends StatelessWidget {
@override
Widget build(BuildContext context) {
// TODO: implement build
return Center(
child: Column(
children: <Widget>[
Container(
margin: EdgeInsets.only(top: 16.0),
width: 300.0,
height: 100.0,
alignment: Alignment.center,
// color: Colors.grey,
child: Text('演示BoxDecoration阴影效果',style: TextStyle(
color: Colors.black,
fontSize: 20.0
),),
decoration: BoxDecoration(
color: Colors.grey,
image: DecorationImage(
image: NetworkImage('http://pic.qqtn.com/up/2016-4/2016042917263628852.jpg'),
alignment: Alignment.topCenter,
fit: BoxFit.fill,
),
boxShadow: [//一组阴影
BoxShadow(
color: Colors.redAccent,//阴影颜色
offset: Offset(0.0, 0.0),//偏移量
blurRadius: 30.0,//模糊范围
spreadRadius: -10.0,//传播范围
)
]
),
),
SizedBox(height: 10.0,),
Container(
width: 300.0,
height: 100.0,
alignment: Alignment.center,
// color: Colors.grey,
child: Text('演示BoxDecoration圆形效果',style: TextStyle(
color: Colors.black,
fontSize: 20.0
),),
decoration: BoxDecoration(
color: Colors.grey,
image: DecorationImage(
image: NetworkImage('http://pic.qqtn.com/up/2016-4/2016042917263628852.jpg'),
alignment: Alignment.topCenter,
fit: BoxFit.fill,
),
shape: BoxShape.circle//设置形状，circle指圆形，rectangle指方形
),
),
SizedBox(height: 10.0,),
Container(
width: 300.0,
height: 100.0,
alignment: Alignment.center,
// color: Colors.grey,
child: Text('演示BoxDecoration--border: BorderDirectional',style: TextStyle(
color: Colors.black,
fontSize: 20.0
),),
decoration: BoxDecoration(
color: Colors.grey,
image: DecorationImage(
image: NetworkImage('http://pic.qqtn.com/up/2016-4/2016042917263628852.jpg'),
alignment: Alignment.topCenter,
fit: BoxFit.fill,
),
border: BorderDirectional(
top: BorderSide(color: Colors.redAccent, width: 2, style: BorderStyle.solid),
start: BorderSide(color: Colors.redAccent, width: 2, style: BorderStyle.solid),
end: BorderSide(color: Colors.redAccent, width: 2, style: BorderStyle.solid),
bottom: BorderSide(color: Colors.redAccent, width: 2, style: BorderStyle.solid),
)
),
),
SizedBox(height: 10.0,),
Container(
width: 300.0,
height: 100.0,
alignment: Alignment.center,
// color: Colors.grey,
child: Text('演示BoxDecoration--border: Border',style: TextStyle(
color: Colors.black,
fontSize: 20.0
),),
decoration: BoxDecoration(
color: Colors.grey,
image: DecorationImage(
image: NetworkImage('http://pic.qqtn.com/up/2016-4/2016042917263628852.jpg'),
alignment: Alignment.topCenter,
fit: BoxFit.fill,
),
// border: Border(
// top: BorderSide(color: Colors.redAccent, width: 2, style: BorderStyle.solid),
// left: BorderSide(color: Colors.redAccent, width: 2, style: BorderStyle.solid),
// right: BorderSide(color: Colors.redAccent, width: 2, style: BorderStyle.solid),
// bottom: BorderSide(color: Colors.redAccent, width: 2, style: BorderStyle.solid),
// ),
border: Border.all(color: Colors.red, width: 3.0, style: BorderStyle.solid)
),
),
SizedBox(height: 10.0,),
Container(
width: 300.0,
height: 100.0,
alignment: Alignment.center,
// color: Colors.grey,
child: Text('演示BoxDecoration的SweepGradient渐变色',style: TextStyle(
color: Colors.black,
fontSize: 20.0
),),
decoration: BoxDecoration(
color: Colors.grey,
// image: DecorationImage(
// image: NetworkImage('http://pic.qqtn.com/up/2016-4/2016042917263628852.jpg'),
// alignment: Alignment.topCenter,
// fit: BoxFit.fill,
// ),
//设置三种渐变色
gradient: SweepGradient(
startAngle: 1.0,
endAngle: pi * 2,
colors: [
Colors.red,
Colors.green
],
// transform: GradientRotation(pi/2)
)
),
),
SizedBox(height: 10.0,),
Container(
width: 300.0,
height: 100.0,
alignment: Alignment.center,
// color: Colors.grey,
child: Text('演示BoxDecoration的RadialGradient渐变色',style: TextStyle(
color: Colors.black,
fontSize: 20.0
),),
decoration: BoxDecoration(
color: Colors.grey,
// image: DecorationImage(
// image: NetworkImage('http://pic.qqtn.com/up/2016-4/2016042917263628852.jpg'),
// alignment: Alignment.topCenter,
// fit: BoxFit.fill,
// ),
gradient: RadialGradient(//渐变色
center: Alignment.centerLeft,
radius: 2.0,
colors: [
Colors.red,
Colors.green
]
)
),
),
SizedBox(height: 10.0,),
Container(
width: 300.0,
height: 100.0,
alignment: Alignment.center,
// color: Colors.grey,
child: Text('演示BoxDecoration的LinearGradient渐变色',style: TextStyle(
color: Colors.black,
fontSize: 20.0
),),
decoration: BoxDecoration(
borderRadius: BorderRadius.all(Radius.circular(12.0)),
color: Colors.grey,
// image: DecorationImage(
// image: NetworkImage('http://pic.qqtn.com/up/2016-4/2016042917263628852.jpg'),
// alignment: Alignment.topCenter,
// fit: BoxFit.fill,
// ),
gradient: LinearGradient(
begin: Alignment.centerLeft,
end: Alignment.centerRight,
colors: [
Colors.red,
Colors.green
]
)
),
),
],
),
);
}
}
运行效果：
