dart - Flutter 以编程方式触发 FutureBuilder

Question

假设我有这样的事情:

return FutureBuilder(
  future: _loadingDeals,
  builder: (BuildContext context, AsyncSnapshot snapshot) {
    return RefreshIndicator(
      onRefresh: _handleRefresh,
        ...
    )
  }
 )

在 _handleRefresh 方法中，我想以编程方式触发 FutureBuilder 的重新运行。

有这种事吗？

用例:

当用户拉下 refreshIndicator 时，_handleRefresh 只会让 FutureBuilder 重新运行。

编辑:

完整的代码片段端到端，没有刷新部分。我已经切换到使用 StreamBuilder，refreshIndicator 部分如何适应所有这些？

class DealList extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => new _DealList();
}

class _DealList extends State<DealList> with AutomaticKeepAliveClientMixin {
  // prevents refreshing of tab when switch to
  // Why? https://stackoverflow.com/q/51224420/1757321
  bool get wantKeepAlive => true; 

  final RestDatasource api = new RestDatasource();
  String token;
  StreamController _dealsController;

  @override
  void initState() {
    super.initState();
    _dealsController = new StreamController();
    _loadingDeals();
  }

  _loadingDeals() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();

    this.token = prefs.getString('token');

    final res =
        this.api.checkInterests(this.token).then((interestResponse) async {
      _dealsController.add(interestResponse);
      return interestResponse;
    });
    return res;
  }

  _handleRefresh(data) async {
    SharedPreferences prefs = await SharedPreferences.getInstance();

    final token = prefs.getString('token');
    await this.api.checkInterests(token).then((interestResponse) {
      _dealsController.add(interestResponse);
    });
    return null;
  }

  @override
  Widget build(BuildContext context) {
    super.build(context); // <-- this is with the wantKeepAlive thing
    return StreamBuilder(
      stream: _dealsController.stream,
      builder: (BuildContext context, AsyncSnapshot snapshot) {

        if (snapshot.hasError) {
          ...
        }

        if (snapshot.connectionState != ConnectionState.done) {
          return Center(
            child: CircularProgressIndicator(),
          );
        }

        if (!snapshot.hasData &&
            snapshot.connectionState == ConnectionState.done) {
          return Text('No deals');
        }

        if (snapshot.hasData) {
          return ListView.builder(
                physics: const AlwaysScrollableScrollPhysics(),
                itemCount: snapshot.data['deals'].length,
                itemBuilder: (context, index) {
                  final Map deal = snapshot.data['deals'][index];
                  return ListTile(
                      onTap: () {
                        Navigator.push(
                          context,
                          MaterialPageRoute(
                            builder: (context) => DealsDetailPage(
                                  dealDetail: deal,
                                ),
                          ),
                        );
                      },
                      title: Text(deal['name']),
                      subtitle: Text(deal['expires']),
                    );
                },
              ),
        }
      },
    );
  }
}

Answer 1

为什么不使用 StreamBuilder 和 Stream 而不是 FutureBuilder？

类似的...

class _YourWidgetState extends State<YourWidget> {
  StreamController<String> _refreshController;

  ...
  initState() {
    super...
    _refreshController = new StreamController<String>();
   _loadingDeals();
  }

  _loadingDeals() {
    _refreshController.add("");
  }

  _handleRefresh(data) {
    if (x) _refreshController.add("");
  }

  ...
  build(context) {
    ...
    return StreamBuilder(
      stream: _refreshController.stream,
      builder: (BuildContext context, AsyncSnapshot snapshot) {
        return RefreshIndicator(
          onRefresh: _handleRefresh(snapshot.data),
            ...
        )
      }
    );
  }
}

我使用 StreamBuilder 创建了一个带有 Flutter 主要示例的 Gist，check it out