布局
基本布局
- GridView(二维滚动列表):比ListView多了一个方向的数据填充。
- ListBody(滚动列表):相比ListView,没有回收复用,简单易用。
- Table(表格布局):子元素类似表格一样在X轴和Y轴排列分布。
- Flow(流式布局):相比Wrap布局的子元素自动换行,Flow需要自行在Delegate里写算法实现换行。
- Wrap(流式布局):子元素在X轴放得下就放,放不下就去下一行的布局。
- ScrollView(滚动视图):一般搭配Column使用的类似滚动列表的布局。
GridView
- 就是二维的ListView
- 有五种构造方式
- GridView()
- GridVIew.builder()
- GridView.costom()
- GirdView.count()
- GridView.extent()
代码
/// GridView()
GridView(gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 3,//交叉轴方向的数目),children: <Widget>[Text('1'),Text('2'),Text('3'),Text('4'),Text('5'),Text('6'),Text('7'),Text('8'),Text('9'),],
),
/// GridView.builder()
final List<String> name = <String>['1','2','3',];
GridView.builder(itemCount: name.length,gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 3,//交叉轴方向item的数量mainAxisSpacing: 2.0,//主轴方向的间隔crossAxisSpacing: 2.0,//交叉轴之间的间隔),itemBuilder: (context, index) {return Container(child: Text(name[index]),);},
),
/// GridView.costom()GridView.custom(gridDelegate: SliverGridDelegateWithMaxCrossAxisExtent(maxCrossAxisExtent: 80.0,//在交叉轴方向上单个item的最大长度crossAxisCount: 3,//交叉轴方向item的数量mainAxisSpacing: 2.0,//主轴方向的间隔),childrenDelegate: SliverChildBuilderDelegate((context, index) {return Container(child: Text(name[index]),);},childCount: name.length,),
),
/// GirdView.count()
GridView.count(crossAxisCount: 3,children: <Widget>[Text('1'),Text('2'),Text('3'),Text('4'),Text('5'),Text('6'),Text('7'),Text('8'),Text('9'),],
),
/// GridView.extent()
GridView.extent(maxCrossAxisExtent: 100.0,//在交叉轴方向上item的最大长度crossAxisCount: 3,//交叉轴方向item的数量mainAxisSpacing: 2.0,//主轴方向的间隔children: <Widget>[Container(child: Text("1"),),Container(child: Text("2"),),Container(child: Text("3"),),],
),
完整示例代码
import 'package:flutter/material.dart';class HomeTabPage1 extends StatelessWidget {List listData = [{"title": "标题1","author": "内容1","image": "https://www.itying.com/images/flutter/1.png"},{"title": "标题2","author": "内容2","image": "https://www.itying.com/images/flutter/2.png"},{"title": "标题3","author": "内容3","image": "https://www.itying.com/images/flutter/3.png"},{"title": "标题4","author": "内容4","image": "https://www.itying.com/images/flutter/4.png"},{"title": "标题5","author": "内容5","image": "https://www.itying.com/images/flutter/5.png"},{"title": "标题6","author": "内容6","image": "https://www.itying.com/images/flutter/6.png"},{"title": "标题7","author": "内容7","image": "https://www.itying.com/images/flutter/7.png"},{"title": "标题8","author": "内容8","image": "https://www.itying.com/images/flutter/1.png"},{"title": "标题9","author": "内容9","image": "https://www.itying.com/images/flutter/2.png"},{"title": "标题1","author": "内容1","image": "https://www.itying.com/images/flutter/1.png"},{"title": "标题2","author": "内容2","image": "https://www.itying.com/images/flutter/2.png"},{"title": "标题3","author": "内容3","image": "https://www.itying.com/images/flutter/3.png"},{"title": "标题4","author": "内容4","image": "https://www.itying.com/images/flutter/4.png"},{"title": "标题5","author": "内容5","image": "https://www.itying.com/images/flutter/5.png"},{"title": "标题6","author": "内容6","image": "https://www.itying.com/images/flutter/6.png"}];List<Widget> _getData() {List<Widget> list = [];for (var i = 0; i < listData.length; i++) {list.add(Container(child: Column(children: [Image.network(listData[i]["image"],fit: BoxFit.cover,),Text(listData[i]["title"],textAlign:TextAlign.center,)],),));}return list;}@overrideWidget build(BuildContext context) {return GridView.count(//设置滚动方向scrollDirection: Axis.vertical,//设置列数crossAxisCount: 5,//设置内边距(整个GridView的)padding: EdgeInsets.all(30),//设置横向间距(3个间距一起用就能控制item各种距离了)crossAxisSpacing: 30,//设置主轴间距mainAxisSpacing: 30,children: _getData(),);}
}
常用参数
gridDelegate
- 有两个实现类
- SliverGridDelegateWithFixedCrossAxisCount
- SliverGridDelegateWithMaxCrossAxisExtent
scrollDirection
* 滚动方向* Axis.vertical* 竖向滚动* Axis.horizontal* 横向滚动
reverse
* 组件反向排序
controller
* 滚动监听
primary
* 值为false,内容不足不可滑动
* 值为true,内容不足可以尝试滑动
shrinkWrap
* 内容适配,默认为false
padding
* 内边距
crossAxisCount
* 列数
mainAxisSpacing
* 主轴之间的间距
crossAxisSpacing
* 横轴之间的间距
childAspectRatio
* 设置宽高的比例
* GridView的子组件直接设置宽高没有反应,可以通过childAspectRatio修改宽高
cacheExtent
* 设置预加载区域
children
* 组件元素 const Widget列表
* 数组内添加widget类型的数据
* flutter的所有组件都是widget,也就是说所有的GridView可以添加所有的组件
semanticChildCount
* 提供语义信息的子组件数量
ListBody
- 很少单独使用,搭配如Row、Column、ListView、Flex一起使用。
代码
Column(//主轴垂直排列的列表,未限制宽,默认将充满屏幕children: <Widget>[ListBody(//指定主轴方向与父框架相同mainAxis: Axis.vertical,reverse: false,//不反向children: <Widget>[Container(color: Colors.red, width: 50.0, height: 50.0),Container(color: Colors.yellow, width: 50.0, height: 50.0),Container(color: Colors.green, width: 50.0, height: 50.0),Container(color: Colors.blue, width: 50.0, height: 50.0),Container(color: Colors.black, width: 50.0, height: 50.0),],)],
)
Table
代码
Container(width: 300.0,height: 200.0,padding: EdgeInsets.all(2.0),color: Color(0xFFC5CAE9),child: Table(//每行中单元格的宽度,TableRow内元素个数,即列数,从第一个到最后一个的宽度//如果排列根据排列方向显示不同columnWidths: const <int, TableColumnWidth>{0: FixedColumnWidth(30.0),1: FixedColumnWidth(70.0),2: FixedColumnWidth(50.0),3: FixedColumnWidth(100.0),},//默认未显示宽度 默认的每一列宽度值,默认情况下均分。defaultColumnWidth: const FlexColumnWidth(1.0),//每个表格的排列方向,此处设置从右到左textDirection: TextDirection.rtl,//表格边框,此处设置蓝色,2像素宽,实线border: TableBorder.all(color: Colors.blue, width: 2.0, style: BorderStyle.solid),//每一个单元格的垂直方向的对齐方式,默认为顶部对齐defaultVerticalAlignment: TableCellVerticalAlignment.top,//基线类型,与TableCellVerticalAlignment.baseline一起使用//textBaseline: null,children: <TableRow>[TableRow(decoration: BoxDecoration(color: Colors.purpleAccent),children: <Widget>[Text('A1'),Text('A2'),Text('A3'),Text('A4'),],),TableRow(decoration: BoxDecoration(color: Colors.purpleAccent),children: <Widget>[Container(color: Colors.red, child: Text('赤')),Container(color: Colors.orange, child: Text('橙')),Container(color: Colors.yellow, child: Text('黄')),Container(color: Colors.green, child: Text('绿')),],),TableRow(children: <Widget>[Text('B1'),Text('B2'),Text('B3'),Text('B4'),]),],),
)
参数
- columnWidth:每列单元格的宽度,int为从0到每行的个数-1
- defaultColumnWidth:默认的每一列宽度值,默认情况下均分。
- textDirection:每列的排列方向,默认从左到右
- border:TableBorder 表格的边框
- defaultVerticalAlignment:单元格默认垂直方向上的对齐方式,默认上对齐TableCellVerticalAlignment.top
- textBaseline:TableCellVerticalAlignment.baseline与此属性配合使用。文本基线类型
- children:存放每行的单元格内容的类别
Flow
FlowDelegate的方法
abstract class FlowDelegate {const FlowDelegate({ Listenable repaint }) : _repaint = repaint;final Listenable _repaint;//重写设置尺寸Size getSize(BoxConstraints constraints) => constraints.biggest;//重写设置约束BoxConstraints getConstraintsForChild(int i, BoxConstraints constraints) => constraints;//绘制children的位置和大小void paintChildren(FlowPaintingContext context);//是否要从新布局,可自己定制规则bool shouldRelayout(covariant FlowDelegate oldDelegate) => false;//是否从新绘制,可自己定制规则bool shouldRepaint(covariant FlowDelegate oldDelegate);@overrideString toString() => '$runtimeType';
}
代码
Flow(delegate: TestFlowDelegate(margin: EdgeInsets.all(5.0)),children: <Widget>[new Container(width: 60.0, height: 60.0, color: Colors.red,child: Text('红'), alignment: Alignment.center, ),new Container(width: 60.0, height: 60.0,color: Colors.orange,child: Text('橙'),alignment: Alignment.center, ),new Container(width: 60.0,height: 60.0,color: Colors.yellow,child: Text('黄'),alignment: Alignment.center, ),new Container(width: 60.0,height: 60.0,color: Colors.green,child: Text('绿'),alignment: Alignment.center, ),new Container(width: 60.0,height: 60.0,color: Colors.cyan,child: Text('青'),alignment: Alignment.center, ),new Container(width: 60.0, height: 60.0,color: Colors.blue,child: Text('蓝'),alignment: Alignment.center, ),new Container(width: 60.0,height: 60.0,color: Colors.purple,child: Text('紫'),alignment: Alignment.center, ),],
)class TestFlowDelegate extends FlowDelegate {EdgeInsets margin = EdgeInsets.zero;TestFlowDelegate({this.margin});@overridevoid paintChildren(FlowPaintingContext context) {var x = margin.left;var y = margin.top;for (int i = 0; i < context.childCount; i++) {var w = context.getChildSize(i).width + x + margin.right;if (w < context.size.width) {context.paintChild(i,transform: new Matrix4.translationValues(x, y, 0.0));x = w + margin.left;} else {x = margin.left;y += context.getChildSize(i).height + margin.top + margin.bottom;context.paintChild(i,transform: new Matrix4.translationValues(x, y, 0.0));x += context.getChildSize(i).width + margin.left + margin.right;}}}@overridebool shouldRepaint(FlowDelegate oldDelegate) {return oldDelegate != this;}
}
Wrap
- 在mainAxis上空间不足时,则向crossAxis上去扩展显示。
- Wrap使用方便一些,但是Flow能实现Wrap,Flow更强一些。
参数
- direction :主轴方向,默认水平
- alignment :主轴方向方式,值为WrapAlignment的枚举值,详情请看Row的对齐方式
- spacing :主轴方向上child之间的间距,默认为0
- runAlignment : 新一行或一列的对齐方式
- runSpacing :新的一行或一列的间距,默认为0
- crossAxisAlignment:交叉轴的对齐方式,默认是从主轴开始位置开始
- textDirection:每一行或一列的排列方式
- 如果一行有三个元素,则第一行取出前三个元素2,1,0这样排列
- verticalDirection:垂直方向上排列方式,值为VerticalDirection的枚举值,默认从上到下
代码
Container(alignment: Alignment.topCenter,child: Wrap(//主轴方向,默认水平direction: Axis.horizontal,//主轴方向方式,包裹在一个控件内效果明显,默认主轴方向开始位置开始alignment: WrapAlignment.spaceBetween,//主轴方向上child之间的间距,默认为0spacing: 6.0,// 新一行或一列的对齐方式runAlignment: WrapAlignment.spaceBetween,//新的一行或一列的间距,默认为0runSpacing: 0.0,//交叉轴的对齐方式,默认是从主轴开始位置开始crossAxisAlignment: WrapCrossAlignment.start,//每一行或一列的排列方式,如果一行有三个元素,则第一行取出前三个元素2,1,0这样排列//默认从左到右textDirection: TextDirection.ltr,//垂直方向上排列方式,默认从上到下verticalDirection: VerticalDirection.down,children: <Widget>[Chip(avatar: CircleAvatar(backgroundColor: Colors.blue.shade900, child: Text('1')),label: Text('Hamilton'),),Chip(avatar: CircleAvatar(backgroundColor: Colors.blue.shade900, child: Text('2')),label: Text('Lafayette'),),Chip(avatar: CircleAvatar(backgroundColor: Colors.blue.shade900, child: Text('3')),label: Text('Mulligan'),),Chip(avatar: CircleAvatar(backgroundColor: Colors.blue.shade900, child: Text('4')),label: Text('Laurens'),),Chip(avatar: CircleAvatar(backgroundColor: Colors.blue.shade900, child: Text('5')),label: Text('Hamilton'),),Chip(avatar: CircleAvatar(backgroundColor: Colors.blue.shade900, child: Text('6')),label: Text('Lafayette'),),Chip(avatar: CircleAvatar(backgroundColor: Colors.blue.shade900, child: Text('7')),label: Text('Mulligan'),),Chip(avatar: CircleAvatar(backgroundColor: Colors.blue.shade900, child: Text('8')),label: Text('Laurens'),),Chip(avatar: CircleAvatar(backgroundColor: Colors.blue.shade900, child: Text('9')),label: Text('Hamilton'),),Chip(avatar: CircleAvatar(backgroundColor: Colors.blue.shade900, child: Text('10')),label: Text('Lafayette'),),Chip(avatar: CircleAvatar(backgroundColor: Colors.blue.shade900, child: Text('11')),label: Text('Mulligan'),),Chip(avatar: CircleAvatar(backgroundColor: Colors.blue.shade900, child: Text('12')),label: Text('Laurens'),),],),
)
ScrollView
SingleChildScrollView
代码
SingleChildScrollView(child: Column(children: <Widget>[Container(height: 200,color: Colors.red,),Container(height: 200,color: Colors.green,),Container(height: 200,color: Colors.blue,),Container(height: 200,color: Colors.yellow,),Container(height: 200,color: Colors.orange,),],),
),
自定义ScrollPhysics控制滑动效果
- 准确的说这个属于所有physics参数共用的一个案例
- 继承ScrollPhysics可以实现自定义滑动的效果
import 'package:flutter/material.dart';void main() {runApp(MyApp());
}class MyCustomScrollPhysics extends ScrollPhysics {const MyCustomScrollPhysics({ScrollPhysics? parent}) : super(parent: parent);@overrideMyCustomScrollPhysics applyTo(ScrollPhysics? ancestor) {return MyCustomScrollPhysics(parent: buildParent(ancestor));}@overridedouble applyBoundaryConditions(ScrollMetrics position, double value) {// 检查是否已经滑动到边界if (value < position.pixels && position.pixels <= position.minScrollExtent) {// 滑动到顶部边界时,允许继续向上滚动return 0.0;} else if (value > position.pixels && position.pixels >= position.maxScrollExtent) {// 滑动到底部边界时,允许继续向下滚动return 0.0;}// 其他情况,使用默认的边界条件return super.applyBoundaryConditions(position, value);}
}class MyApp extends StatelessWidget {@overrideWidget build(BuildContext context) {return MaterialApp(home: Scaffold(body: CustomScrollView(physics: MyCustomScrollPhysics(), // 使用自定义的ScrollPhysicsslivers: <Widget>[SliverAppBar(expandedHeight: 200.0,pinned: true,flexibleSpace: FlexibleSpaceBar(title: Text('Custom Scroll Physics Example'),),),SliverList(delegate: SliverChildBuilderDelegate((BuildContext context, int index) {return ListTile(title: Text('Item $index'),);},childCount: 100, // 你的列表项数量),),],),),);}
}