对StreamBuilder中每个DocumentSnapshot的附加查询 [英] Additional query for every DocumentSnapshot within StreamBuilder

问题描述

我需要查询StreamBuilder返回的每个DocumentSnapshot的其他数据，但是我不能异步返回itemBuilder函数，因此可以在其中使用await. 那条留言message.loadUser();是我尝试查询Firestore的尝试，但没有解决问题.

I need to query additional data for every DocumentSnapshot returned by the StreamBuilder, but I can't return the itemBuilder function asynchronously so that I can use await within it. That commented message.loadUser(); was my attempt to query firestore but didn't do the trick.

StreamBuilder(
                  stream: Firestore.instance
                      .collection("messages").snapshots(),
                  builder: (context, snapshot) {
                    switch (snapshot.connectionState) {
                      case ConnectionState.none:
                      case ConnectionState.waiting:
                        return Center(
                          child: PlatformProgressIndicator(),
                        );
                      default:
                        return ListView.builder(
                          reverse: true,
                          itemCount: snapshot.data.documents.length,
                          itemBuilder: (context, index) {
                            List rev = snapshot.data.documents.reversed.toList();
                            ChatMessageModel message = ChatMessageModel.fromSnapshot(rev[index]);
                            //message.loadUser();
                            return ChatMessage(message);
                          },
                        );
                    }
                  },
                )

推荐答案

找到了解决方案，只是不确定它是否更简单. 将itemBuilder返回的小部件更改为Stateful，并使用FutureBuilder.

Found a solution, just not sure it's the simpler one. Changed the widget returned by the itemBuilder to Stateful and used a FutureBuilder.

class ChatMessage extends StatefulWidget {
  final ChatMessageModel _message;

  ChatMessage(this._message);
  @override
  _ChatMessageState createState() => _ChatMessageState(_message);
}

class _ChatMessageState extends State<ChatMessage> {
  final ChatMessageModel _message;

  _ChatMessageState(this._message);

  Future<ChatMessageModel> _load() async {
    await _message.loadUser();
    return _message;
  }

  @override
  Widget build(BuildContext context) {

    return Container(
      margin: const EdgeInsets.symmetric(horizontal: 10.0, vertical: 10.0),
      child: FutureBuilder(
        future: _load(),
        builder: (context, AsyncSnapshot<ChatMessageModel>message) {
          if (!message.hasData)
            return Container();
          return Row(
            children: <Widget>[
              Container(
                margin: const EdgeInsets.only(right: 16.0),
                child: GestureDetector(
                  child: CircleAvatar(
                    backgroundImage: NetworkImage(message.data.user.pictureUrl),
                  ),
                  onTap: () {
                    Navigator.of(context)
                        .push(MaterialPageRoute(builder: (context) => 
                        ProfileScreen(message.data.user)));
                  },
                ),
              ),
              Expanded(
                child: Column(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: <Widget>[
                    Text(
                      message.data.user.name,
                      style: Theme.of(context).textTheme.subhead,
                    ),
                    Container(
                        margin: const EdgeInsets.only(top: 5.0),
                        child: _message.mediaUrl != null
                            ? Image.network(_message.mediaUrl, width: 250.0)
                            : Text(_message.text))
                  ],
                ),
              )
            ],
          );
        },
      ),
    );
  }
}

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