前言
Flutter是谷歌的移动UI框架，可以快速在iOS和Android上构建高质量的原生用户界面。
IT界著名的尼古拉斯·高尔包曾说：轮子是IT进步的阶梯！热门的框架千篇一律，好用轮子万里挑一！Flutter作为这两年开始崛起的跨平台开发框架，其第三方生态相比其他成熟框架还略有不足，但轮子的数量也已经很多了。本系列文章挑选日常app开发常用的轮子分享出来，给大家提高搬砖效率，同时也希望flutter的生态越来越完善，轮子越来越多。
本系列文章准备了超过50个轮子推荐，工作原因，尽量每1-2天出一篇文章。
tip:本系列文章合适已有部分flutter基础的开发者，入门请戳：flutter官网
正文
轮子
- 轮子名称：sticky_headers
- 轮子概述：flutter给滚动内容添加粘性header组件.
- 轮子作者：fluttercommunity.dev(官方)
- 推荐指数：★★★★
- 常用指数：★★★★
-
效果预览：
sticky_headers (1).gif
安装
dependencies:
sticky_headers: ^0.1.8+1
import 'package:sticky_headers/sticky_headers.dart';
使用方法
在列表项中，使用StickyHeader()，基本用法：（gif效果图中的默认效果）
ListView.builder(
itemCount: 12,
itemBuilder: (context, index) {
return StickyHeader(
header: Container( //header组件
height: 50.0,
color: Colors.blueGrey[700],
padding: EdgeInsets.symmetric(horizontal: 16.0),
alignment: Alignment.centerLeft,
child: Text('Header #$index',
style: const TextStyle(color: Colors.white),
),
),
content: Container(//内容组件
child: Image.network(imgs[index], fit: BoxFit.cover,width: double.infinity, height: 200.0),
),
);
}
)
在列表项中，使用StickyHeaderBuilder()来自定义更多的header效果和事件：（gif效果图中的自定义header效果）
ListView.builder(
itemCount: 12,
itemBuilder: (context, index) {
return StickyHeaderBuilder(
builder: (BuildContext context, double stuckAmount) {
stuckAmount = 1.0 - stuckAmount.clamp(0.0, 1.0);
return new Container(
height: 50.0,
color: Color.lerp(Colors.blue[700], Colors.red[700], stuckAmount),
padding: new EdgeInsets.symmetric(horizontal: 16.0),
alignment: Alignment.centerLeft,
child: new Row(
children: <Widget>[
new Expanded(
child: new Text('Header #$index',
style: const TextStyle(color: Colors.white),
),
),
new Offstage(
offstage: stuckAmount <= 0.0,
child: new Opacity(
opacity: stuckAmount,
child: new IconButton(
icon: new Icon(Icons.favorite, color: Colors.white),
onPressed: () =>
Scaffold.of(context).showSnackBar(
new SnackBar(content: new Text('Favorite #$index'))
),
),
),
),
],
),
);
},
content: new Container(
child: new Image.network(imgs[index], fit: BoxFit.cover,
width: double.infinity, height: 200.0),
),
);
}
)
在列表项中，使用StickyHeaderBuilder()，overlapHeaders=true,使header悬浮在内容上：（gif效果图中的header浮动）
ListView.builder(
itemCount: 12,
itemBuilder: (context, index) {
return new StickyHeaderBuilder(
overlapHeaders: true,
builder: (BuildContext context, double stuckAmount) {
stuckAmount = 1.0 - stuckAmount.clamp(0.0, 1.0);
return new Container(
height: 50.0,
color: Colors.grey[900].withOpacity(0.6 + stuckAmount * 0.4),
padding: new EdgeInsets.symmetric(horizontal: 16.0),
alignment: Alignment.centerLeft,
child: new Text('Header #$index',
style: const TextStyle(color: Colors.white),
),
);
},
content: new Container(
child: new Image.network(imgs[index], fit: BoxFit.cover,
width: double.infinity, height: 200.0),
),
);
}
)
数据分组，在content中渲染子列表，形成类似RN的SectionList：（gif效果图中的SectionList效果）
class StickyHeadersDemo4 extends StatefulWidget {
StickyHeadersDemo4({Key key}) : super(key: key);
@override
_demoState createState() => _demoState();
}
class _demoState extends State<StickyHeadersDemo4> {
List data=[{
"latter":"A",
"group":[
"A分组1","A分组1","A分组1","A分组1","A分组1","A分组1"
]
},{
"latter":"B",
"group":[
"B分组1","B分组1","B分组1","B分组1","B分组1","B分组1"
]
},{
"latter":"C",
"group":[
"C分组1","C分组1","C分组1","C分组1","C分组1","C分组1"
]
},{
"latter":"D",
"group":[
"D分组1","D分组1","D分组1","D分组1","D分组1","D分组1"
]
},{
"latter":"E",
"group":[
"E分组1","E分组1","E分组1","E分组1","E分组1","E分组1"
]
}];
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("sticky_headers"),
actions: <Widget>[
GoWeb(pluginName: 'sticky_headers')
],
),
body: ListView.builder(
itemCount: data.length,
itemBuilder: (context, index) {
return StickyHeader(
header: Container(
height: 50.0,
color: Colors.blueGrey[700],
padding: EdgeInsets.symmetric(horizontal: 16.0),
alignment: Alignment.centerLeft,
child: Text(data[index]['latter'],
style: const TextStyle(color: Colors.white),
),
),
content: Column(
children: buildGroup(data[index]['group']),
),
);
}
)
);
}
List<Widget> buildGroup(List group){
return group.map((item){
return Container(
height: 60,
alignment: Alignment.centerLeft,
padding: EdgeInsets.only(left: 20),
child: Text(item),
);
}).toList();
}
}
