Flutter中FutureBuilder和StreamBuilder

在 Flutter 中，如果你想让 FutureBuilder 的 future 函数再次执行，可以通过以下几种方式实现：

---

方法 1：使用 Key 强制重建 FutureBuilder

通过改变 FutureBuilder 的 key，可以强制 Flutter 重建它，从而重新执行 future 函数：

class MyWidget extends StatefulWidget {@override_MyWidgetState createState() => _MyWidgetState();
}class _MyWidgetState extends State<MyWidget> {// 使用 UniqueKey 来强制重建 FutureBuilderUniqueKey _futureBuilderKey = UniqueKey();Future<String> fetchData() async {// 模拟网络请求await Future.delayed(Duration(seconds: 2));return "New Data: ${DateTime.now()}";}void _refreshData() {setState(() {// 改变 key，FutureBuilder 会重新执行 future_futureBuilderKey = UniqueKey();});}@overrideWidget build(BuildContext context) {return Column(children: [ElevatedButton(onPressed: _refreshData,child: Text("Refresh Data"),),FutureBuilder<String>(key: _futureBuilderKey, // 关键点：改变 key 会重建 FutureBuilderfuture: fetchData(),builder: (context, snapshot) {if (snapshot.connectionState == ConnectionState.waiting) {return CircularProgressIndicator();}if (snapshot.hasError) {return Text("Error: ${snapshot.error}");}return Text("Data: ${snapshot.data}");},),],);}
}

---

方法 2：使用 StatefulWidget 管理 future

在 StatefulWidget 中存储 future，并在需要刷新时重新调用 fetchData：

class MyWidget extends StatefulWidget {@override_MyWidgetState createState() => _MyWidgetState();
}class _MyWidgetState extends State<MyWidget> {Future<String>? _futureData;Future<String> fetchData() async {await Future.delayed(Duration(seconds: 2));return "New Data: ${DateTime.now()}";}@overridevoid initState() {super.initState();_futureData = fetchData(); // 初始化 future}void _refreshData() {setState(() {_futureData = fetchData(); // 重新赋值 future});}@overrideWidget build(BuildContext context) {return Column(children: [ElevatedButton(onPressed: _refreshData,child: Text("Refresh Data"),),FutureBuilder<String>(future: _futureData,builder: (context, snapshot) {if (snapshot.connectionState == ConnectionState.waiting) {return CircularProgressIndicator();}if (snapshot.hasError) {return Text("Error: ${snapshot.error}");}return Text("Data: ${snapshot.data}");},),],);}
}

---

方法 3：使用 StreamBuilder 替代 FutureBuilder

如果数据需要频繁刷新，可以考虑使用 Stream + StreamBuilder：

class MyWidget extends StatefulWidget {@override_MyWidgetState createState() => _MyWidgetState();
}class _MyWidgetState extends State<MyWidget> {final StreamController<String> _streamController = StreamController();Future<String> fetchData() async {await Future.delayed(Duration(seconds: 2));return "New Data: ${DateTime.now()}";}void _refreshData() {fetchData().then((data) {_streamController.add(data); // 手动推送新数据到 Stream});}@overridevoid initState() {super.initState();_refreshData(); // 初始化数据}@overridevoid dispose() {_streamController.close();super.dispose();}@overrideWidget build(BuildContext context) {return Column(children: [ElevatedButton(onPressed: _refreshData,child: Text("Refresh Data"),),StreamBuilder<String>(stream: _streamController.stream,builder: (context, snapshot) {if (snapshot.connectionState == ConnectionState.waiting) {return CircularProgressIndicator();}if (snapshot.hasError) {return Text("Error: ${snapshot.error}");}return Text("Data: ${snapshot.data}");},),],);}
}

---

总结

方法	适用场景	特点
改变 Key	简单场景	强制重建 FutureBuilder，适合一次性刷新
重新赋值 future	推荐方式	通过 setState 更新 future，逻辑清晰
StreamBuilder	频繁刷新	适合需要持续监听数据变化的场景

选择最适合你需求的方式即可！