Shulou(Shulou.com)06/03 Report--

本篇内容主要讲解"FlutterListView怎么实现上拉加载更多下拉刷新的功能"，感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷，实用性强。下面就让小编来带大家学习"FlutterListView怎么实现上拉加载更多下拉刷新的功能"吧!

下拉刷新

跟原生开发一样，下拉刷新在flutter里提供的有组件实现 RefreshIndicator

一直不明白为啥组件中都提供下拉刷新，但就是没有上拉加载!!

我这请求接口数据用的是 http 库，是个第三方的是需要安装的 https://pub.dev/packages/http

用法如下

class MyHomePage extends StatefulWidget { MyHomePage({Key key}) : super(key: key); @override MyHomeWidget2 createState() => MyHomeWidget2();}class MyHomeWidget2 extends State { 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 _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(); }, ) )); }}

上拉加载

上拉加载原理还是一样的，给ListView加一个 ScrollController 组件，然后通过事件监听滚动条的高度来显示和隐藏加载更多的组件

先将加载更多的组件写好

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

初始化一个 ScrollController 组件，将其设置给 ListView 组件的 controller 属性上

ScrollController _scrollController = new ScrollController();child: ListView.separated( controller: _scrollController, //...)

然后通过重写 dispost() 方法来处理加载更多组件的释放

@overridevoid dispose() { _scrollController.dispose(); super.dispose();}

最后通过数据源来控制界面渲染哪个组件，当数据源循环渲染的 index 跟数据源一样长时（其实少1，下标从0开始的）就渲染加载更多组件，让其显示出来，同时调用加载更多方法，获取数据，再通过state实现组件ui的更新

完整代码如下

class MyHomePage extends StatefulWidget { MyHomePage({Key key}) : super(key: key); @override MyHomeWidget2 createState() => MyHomeWidget2();}class MyHomeWidget2 extends State { 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 _onRefresh() { data.clear(); this.page = 1; return _fetchData().then((data) { setState(() => this.data.addAll(data)); }); } Future _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(); }, ) )); }}到此，相信大家对"FlutterListView怎么实现上拉加载更多下拉刷新的功能"有了更深的了解，不妨来实际操作一番吧!这里是网站，更多相关内容可以进入相关频道进行查询，关注我们，继续学习!

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