ListView是最常用的可滚动组件之一，它可以沿一个方向线性排布所有子组件，并且它也支持列表项懒加载（在需要时才会创建）。

我们看看ListView的默认构造函数定义：

ListView({  ...    //可滚动widget公共参数  Axis scrollDirection = Axis.vertical,  bool reverse = false,  ScrollController? controller,  bool? primary,  ScrollPhysics? physics,  EdgeInsetsGeometry? padding,    //ListView各个构造函数的共同参数    double? itemExtent, // 该参数如果不为null，则会强制children的“长度”为itemExtent的  Widget? prototypeItem, //通知list 我所有的子项都和这个的高度一样 ,方便计算    // 该属性表示是否根据子组件的总长度来设置ListView的长度  //当ListView在一个无边界(滚动方向上)的容器中时，shrinkWrap必须为true。  bool shrinkWrap = false,     bool addAutomaticKeepAlives = true,  bool addRepaintBoundaries = true,  double? cacheExtent, // 预渲染区域长度      //子widget列表  List<Widget> children = const <Widget>[],})

class ListViewState1 extends StatelessWidget{  @override  Widget build(BuildContext context) {    // TODO: implement build    return ListView(      shrinkWrap: true,      padding: EdgeInsets.all(20),      children: const <Widget>[        Text('Im dedicating every day to you',style: TextStyle(height: 2),),        Text('Domestic life was never quite my style',style: TextStyle(height: 2),),        Text('When you smile, you knock me out, I fall apart',style: TextStyle(height: 2),),        Text('And I thought I was so smart',style: TextStyle(height: 2),),        Text('Im dedicating every day to you',style: TextStyle(height: 2),),        Text('Domestic life was never quite my style',style: TextStyle(height: 2),),        Text('When you smile, you knock me out, I fall apart',style: TextStyle(height: 2),),        Text('And I thought I was so smart',style: TextStyle(height: 2),),        Text('Im dedicating every day to you',style: TextStyle(height: 2),),        Text('Domestic life was never quite my style',style: TextStyle(height: 2),),        Text('When you smile, you knock me out, I fall apart',style: TextStyle(height: 2),),        Text('And I thought I was so smart',style: TextStyle(height: 2),),      ],    );  }}

**ListView.builder** 适合列表项比较多或者列表项不确定的情况```dartitemBuilder：它是列表项的构建器itemCount：列表项的数量，如果为null，则为无限列表。```

// ListView.builder + prototypeItem +  itemCount 展示 // ListTile 一个 简单的组件class ListViewState3 extends StatelessWidget{  @override  Widget build(BuildContext context) {    // TODO: implement build    return ListView.builder(      prototypeItem: ListTile(title: Text("1")),      itemCount: 56,      itemBuilder: (context, index) {        return ListTile(title: Text("$index"));      },    );  }}

ListView.separated可以在生成的列表项之间添加一个分割组件，它比ListView.builder多了一个separatorBuilder参数，该参数是一个分割组件生成器。

class ListViewState4 extends StatelessWidget{  //下划线widget预定义以供复用。  Widget divider1=Divider(color: Colors.blue,);  Widget divider2=Divider(color: Colors.green);  List<String> list2 = [    "1","2","3","4","5",    "1","2","3","4","5",    "1","2","3","4","5",    "1","2","3","4","5",    "1","2","3","4","5",    "1","2","3","4","5",    "1","2","3","4","5"];  @override  Widget build(BuildContext context) {    // TODO: implement build    return Scrollbar(child: ListView.separated(        itemCount: list2.length,        itemBuilder: (BuildContext context ,int index){          return ListTile(title: Text(list2[index]));        },        separatorBuilder: (BuildContext context, int index) {          return index%2==0?divider1:divider2;        },    ));  }}

给列表指定 itemExtent 或 prototypeItem 会有更高的性能，所以当我们知道列表项的高度都相同时，强烈建议指定 itemExtent 或 prototypeItem

实例 : 给一个listview 动态添加数据

1 动态添加需要 State 所有需要构建 StatefulWidget

class MyListViewState0 extends StatefulWidget {  const MyListViewState0({Key? key}) : super(key: key);  @override  State<MyListViewState0> createState() => _MyState0();}

class _MyState0 extends State<MyListViewState0> {  // 初始化 数据源  List<String> list2 = [    "1","2","3","4","5",    "1","2","3","4","5",    "1","2","3","4","5",    "1","2","3","4","5",    "1","2","3","4","5",    "1","2","3","4","5",    "1","2","3","4","5"];  @override  Widget build(BuildContext context) {    return ConstrainedBox(        constraints: BoxConstraints.tightFor(width: double.infinity),        child: Column(          children: <Widget>[            ElevatedButton(onPressed: (){          		// 刷新state            		setState(() {          			//点击按钮时 itemss 自加一                 itemss ++ ;          			// 添加到数据中                 list2.insert(0, "-----------$itemss");              });            }, child: Text("点击1")),            Expanded(child:  ListViewState2(list2))          ],        )    );  }}

class ListViewState2 extends StatelessWidget{  List<String> list = [] ;  ListViewState2(List<String> item,{Key? key}) : super(key: key){    list = item ;  }  @override  Widget build(BuildContext context) {    // TODO: implement build    return Scrollbar(child: ListView.builder(        itemCount: list.length,        itemExtent: 50,        itemBuilder: (BuildContext context ,int index){          return Text(list[index]);        }    ));  }}