在 Material App 之前访问时为 Null BuildContext

Question

当试图访问上下文时，它返回 null（脏上下文）。对此有任何建议。我试图在 main() 函数之后直接访问。

class App extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final bloc = Provider.of(context);
        return Provider(
      child: StreamBuilder(
          stream:
              Rx.combineLatestList([bloc] as List<Stream<dynamic>>),
          builder: (context, snapshot) {
            return MaterialApp(
              debugShowCheckedModeBanner: false,
              home: MyHomePage(),

           );
          }),
    );
  }
}

Answer 1

您必须确保您已收到来自流构建器的数据：

class App extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final bloc = Provider.of(context);
        return Provider(
      child: StreamBuilder(
          stream:
              Rx.combineLatestList([bloc] as List<Stream<dynamic>>),
          builder: (context, snapshot) {
          if (snapshot.connectionState == ConnectionState.done && snapshot.hasData) {
              return MaterialApp(
                  debugShowCheckedModeBanner: false,
                  home: MyHomePage(),
              );
          }
          else
              return CircularProgressIndicator();
          }),
    );
  }
}