如何创建 StreamBuilder<UserModel> 实例

Question

我的代码中有这部分我想在整个项目中重复，我希望能够在其他地方调用这个函数，但问题是你需要将 snapshot.data 传递给 widget 下树，有什么办法吗？

Widget UserStreamBuilderShortcut(BuildContext context, Widget widget){

  final _user = Provider.of<UserModel>(context);

  return

    StreamBuilder<UserModel>(
      stream: UserProvider(userID: _user.userID).userData,
      builder: (context, snapshot){
        if(snapshot.hasData == false){
          return LoadingFullScreenLayer();
        } else {
          UserModel userModel = snapshot.data; // cant pass this to instances of UserStreamBuilderShortcut Widget
          return
            widget; // in instances of this UserStreamBuilderShortcut we need to be able to pass snapshot.data here
        }
      },
    );

}

Answer 1

您可以为此指定构建器参数

// define a Function type that takes a BuildContext and UserModel
// and returns a Widget
typedef UserModelWidgetBuilder = Widget Function(
  BuildContext context,
  UserModel userModel,
);

// pass it as a parameter in the shortcut function
Widget UserStreamBuilderShortcut({
  BuildContext context,
  UserModelWidgetBuilder builder,
}) {
  final _user = Provider.of<UserModel>(context);

  return StreamBuilder<UserModel>(
    stream: UserProvider(userID: _user.userID).userData,
    builder: (context, snapshot) {
      if (snapshot.hasData == false) {
        return LoadingFullScreenLayer();
      } else {
        UserModel userModel = snapshot.data;
        return builder(context, userModel);
      }
    },
  );
}

现在可以这样调用了：

UserStreamBuilderShortcut(
  context: context,
  builder: (context, UserModel userModel) {
    return Container(); // create widget with UserModel
  },
),

Answer 2

如果您使用 Provider 包，您可以从它的子窗口小部件调用它的流参数。

父控件：

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return StreamProvider<BrewList>.value(
      value: Database().brewList,
      child: MaterialApp(
        home: BrewListTile(),
      ),
    );
  }
}

有权访问流的子微件。

class _BrewListState extends State<BrewList> {
  @override
  Widget build(BuildContext context) {
    final brews = Provider.of<List<Brew>>(context) ?? [];
    return Text(brews[0].text);

如何创建 StreamBuilder<UserModel> 实例

how to create instances of StreamBuilder<UserModel>

dart

flutter

stream-builder