How do I get data from multiple documents with StreamBuilder?

Question

I am trying to make my Flutter app with chat.
I use a streambuilder to update the chat data.

My problem is i don't know how i can read multiple documents with streambuilder.

Here my database:

My plan i would like get all data from this documents.
Before, i storage the id in a object and i use a for loop to get all data from documents.
The documents can be a random count (2 or 10...).

Here my streambuilder:

body() {
  //build stream link get id
  Stream _build_stream_id() async* {
    //load user
    var user_id = await StorageUserID.loadData();
    yield* FirebaseFirestore.instance
        .collection('chat')
        .doc('users')
        .collection(user_id)
        .snapshots();
  }

  //build stream link get data
  Stream _build_stream_data(chat_overview_object, index) async* {
    yield* FirebaseFirestore.instance
        .collection('chat')
        .doc('chat_overview_data')
        .collection('data')
        .doc(chat_overview_object[index].chat_overview_id[0])
        .snapshots();
  }

  return StreamBuilder(
    stream: _build_stream_id(),
    builder: (context, snapshot) {
      if (snapshot.hasData) {
        var chat_overview_object = query_chat_overview_data_1(snapshot.data);
        for (var i = 0; i < chat_overview_object.length; i++) {
          return StreamBuilder(
            stream: _build_stream_data(chat_overview_object, i),
            builder: (context, snapshot) {
              if (snapshot.hasData) {
                return Text('test: ' + snapshot.data.toString());
              } else {
                return Text("No data");
              }
            },
          );
        }
      } else {
        return Text("No data");
      }
      return Text('data');
    },
  );
}

If you find a better way pls tell me. If you have questions, feel free to ask me.
Many thx (:

Answer 1

You can combine streams using the StreamGroup from the async package.

import 'package:async/async.dart' show StreamGroup;

List<Stream> streamList = [stream1, stream2];

Stream combinedStream = StreamGroup.merge(streamList);

Though handling Firestore sollections with different fields might be tricky.