firebase - StreamBuild:流，调用返回Firestore流的方法直到更新才检索数据

Question

我希望有人能解释为什么显式调用Firestore.instance.collection('data')。snapshots()与调用包含Firestore.instance.collection('data')。snapshots( )并返回一个Stream。

调用包含Firestore.instance.collection('data')。snapshots()的方法仅在对Firestore数据进行更改后才能获取数据快照。

class GlobalAppModel extends Model{
......//other global data elements

  Stream getDataStreamSnapshots(){
    Firestore.instance.collection('data').snapshots();
  }
}

class DataDetailWidget2 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    dataStream = AppModel.of(context);
    ....
    body: Container(
        child: StreamBuilder(
          stream: Firestore.instance.collection('data').snapshots(), //This works great.
          //stream: dataStream.getDataStreamSnapshots(), //This does not grab a snapshot until firestore is updated.
          builder: (context, snapshot) { 
            .....
          }

    ....
  }

}

Answer 1

您只是在getDataStreamSnapshots方法中缺少return关键字。

class GlobalAppModel extends Model{
......//other global data elements

  Stream getDataStreamSnapshots(){
    return Firestore.instance.collection('data').snapshots(); // return added
  }
}