Flutter ListView 上拉加载更多下拉刷新功能实现方法

class MyHomePage extends StatefulWidget {
 MyHomePage({Key key}) : super(key: key);
 @override
 MyHomeWidget2 createState() => MyHomeWidget2();
}
class MyHomeWidget2 extends State<MyHomePage> {
 int page = 1;
 List data = new List();
 var baseUrl = "https://cnodejs.org/api/v1";
 @override
 void initState() {
 super.initState();
 this._onRefresh();
 }
 _fetchData() async {
 var response = await http.get(
  '${this.baseUrl}/topics?mdrender=false&limit=10&page=${this.page}');
 var json = await convert.jsonDecode(response.body);
 return json['data'];
 }
 Future<dynamic> _onRefresh() {
 data.clear();
 this.page = 1;
 return _fetchData().then((data) {
  setState(() => this.data.addAll(data));
 });
 }
 @override
 Widget build(BuildContext context) {
 return Scaffold(
  body: RefreshIndicator( // 在ListView外包一层 RefreshIndicator 组件
  onRefresh: _onRefresh, // 添加onRefresh方法
  child: ListView.separated(
   itemCount: this.data.length,
   itemBuilder: (context, index) {
   var _data = this.data[index];
   return ListTile(
    leading: Image.network(_data["author"]["avatar_url"]),
    title: Text(_data["title"]),
    subtitle: Text(_data["author"]["loginname"] +
     " created at " +
     new DateTime.now().toString()), // 为了看每次数据变动，这里直接取当前时间
    trailing: Icon(Icons.chevron_right));
   },
   separatorBuilder: (context, index) {
   return Divider();
   },
  )
 ));
 }
}

Widget _loadMoreWidget() {
 return new Padding(
 padding: const EdgeInsets.all(15.0), // 外边距
 child: new Center(
  child: new CircularProgressIndicator()
 ),
 );
}

ScrollController _scrollController = new ScrollController();

child: ListView.separated(
 controller: _scrollController,
 //...
)

@override
void dispose() {
 _scrollController.dispose();
 super.dispose();
}

class MyHomePage extends StatefulWidget {
 MyHomePage({Key key}) : super(key: key);
 @override
 MyHomeWidget2 createState() => MyHomeWidget2();
}
class MyHomeWidget2 extends State<MyHomePage> {
 int page = 1;
 bool isLoadmore = false;
 List data = new List();
 var baseUrl = "https://cnodejs.org/api/v1";
 ScrollController _scrollController = new ScrollController();
 @override
 void initState() {
 super.initState();
 this._onRefresh();
 _scrollController.addListener(() {
  if (_scrollController.position.pixels == _scrollController.position.maxScrollExtent) {
  _onLoadmore();
  }
 });
 }
 _fetchData() async {
 var response = await http.get(
  '${this.baseUrl}/topics?mdrender=false&limit=10&page=${this.page}');
 var json = await convert.jsonDecode(response.body);
 return json['data'];
 }
 Future<dynamic> _onRefresh() {
 data.clear();
 this.page = 1;
 return _fetchData().then((data) {
  setState(() => this.data.addAll(data));
 });
 }
 Future<dynamic> _onLoadmore() {
 this.page++;
 return _fetchData().then((data) {
  setState((){
  this.data.addAll(data);
  isLoadmore = false;
  });
 });
 }
 @override
 void dispose() {
 _scrollController.dispose();
 super.dispose();
 }
 Widget _loadMoreWidget() {
 return new Padding(
  padding: const EdgeInsets.all(15.0),
  child: new Center(
  child: new CircularProgressIndicator()
  ),
 );
 }
 @override
 Widget build(BuildContext context) {
 return Scaffold(
  body: RefreshIndicator(
  onRefresh: _onRefresh,
  child: ListView.separated(
   controller: _scrollController,
   itemCount: this.data.length,
   itemBuilder: (context, index) {
   if (index == data.length - 1) {
    return _loadMoreWidget();
   } else {
    var _data = this.data[index];
    return ListTile(
     leading: Image.network(_data["author"]["avatar_url"]),
     title: Text(_data["title"]),
     subtitle: Text(_data["author"]["loginname"] +
      " created at " +
      new DateTime.now().toString()),
     trailing: Icon(Icons.chevron_right));
   }
   },
   separatorBuilder: (context, index) {
   return Divider();
   },
  )
 ));
 }
}