Flutter：如何将事件添加到现有流？

Question

我在 StreamProvider 中使用

FirebaseAuth.instance.idTokenChanges()

返回的 Stream，每次用户注册/登录/退出时更新整个底层 Widget-tree。

例如，当我更新 displayName 时，有没有办法手动向该 Stream 添加事件，以便 StreamBuidler 使用新用户数据（新 displayName）重建小部件树，以便在 UI 中显示更改？

我是否可以访问与流关联的控制器，以便我可以在其上调用

.sink.add()

？或者有什么别的办法吗？

Answer 1

我想出了一个解决方案：使用 StreamGroup 类将两个（或多个）流合并为一个。

重要，这是来自 Flutter async 包，而不是 dart async：

import 'dart:async'; //async await and all that...
import 'package:async/async.dart'; //this contains StreamGroup

...

  static StreamController<User> _ctrl;
  static Future<void> initCombinedStream() async {

    //without the following line, I get this Error on hot restart: "Bad state: Stream has already been listened to."
    //maybe that error could also be caused by other reasons
    dispose();

    _ctrl = StreamController<User>();

    StreamGroup streamGroup = StreamGroup<User>();
    await streamGroup
      ..add(_ctrl.stream) //I use this stream when I want to update user info from my code
      ..add(FirebaseAuth.instance.idTokenChanges()) //normal firebase stuff...
      ..close();
    _combinedStream = streamGroup.stream;
  }

  ///this is also called from the overridden dispose() method of the highest StatefulWidget in my app
  static void dispose() {
    if (_ctrl != null) _ctrl.close();
  }

  //called when updating displayName for example, otherwise that wouldn't update in the UI
  static void updateUserStream() {
    await FirebaseAuth.instance.currentUser.reload(); //no need to call this, this User object is already updated
    _ctrl.add(FirebaseAuth.instance.currentUser); 
  }