StreamBuilder in Flutter stuck with ConnectionState.waiting and displays only the loading mark

问题

Hi I am trying to display the data inside the Firebase documents into my Flutter dynamically where they get rendered using a loop, so I made a List<Widget> Cards and added to it the function makeItem() that contains the cards, and put them inside a loop, so the problem is that when I run the code it outputs print(snapshot.connectionState); as ConnectionState.waiting all the time and it should be async snapshot yet it refuses to load the data as required, I should mention that the data is display as wanted when I hit "Hot reload in Android Studio" . so I don't know how resolve this issue. Thanks in Advance

回答1:

Can you try the following?

class MyList extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return StreamBuilder<QuerySnapshot>(
      stream: _firestore.collection(widget.city).snapshots(),
      builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
        if (snapshot.hasError)
          return Text('Error: ${snapshot.error}');
        switch (snapshot.connectionState) {
          case ConnectionState.waiting: return Center(child: CircularProgressIndicator(backgroundColor: Colors.amber,strokeWidth: 1),),
          default:
            return ListView(
              children: snapshot.data.documents.map((DocumentSnapshot document) {
                return makeItem(
                  pointName: document['name'],
                  huge: document['lastname'],
                  moderate: document['mobileNumber'],
                  none: document['location'],
                  fights: document['job'],
               );
              }).toList(),
           );
        }
      },
    );
  }
}

回答2:

I think I got something for you try this out. It works on my emulator.

List<Widget> cards = [];
  Stream<QuerySnapshot> firebaseStream;

  @override
  void initState() {
    super.initState();
    firebaseStream = Firestore.instance.collection('Hearings').snapshots();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SafeArea(
        child: StreamBuilder<QuerySnapshot>(
          stream: firebaseStream,
          builder: (BuildContext context,
              AsyncSnapshot<QuerySnapshot> asyncSnapshot) {
            List<DocumentSnapshot> snapData;

            if (asyncSnapshot.connectionState == ConnectionState.waiting) {
              return Container(
                child: Center(
                  child: CircularProgressIndicator(
                    backgroundColor: Colors.amber,
                    strokeWidth: 1,
                  ),
                ),
              );
            } else if (asyncSnapshot.connectionState ==
                ConnectionState.active) {
              snapData = asyncSnapshot.data.documents;
              if (asyncSnapshot.hasData) {
                for (int i = 0; i < snapData.length; i++) {
                  Widget card = Text(snapData[i].data['locationName']);

                  cards.add(card);
                }
              }
            }
            return ListView.builder(
              itemCount: cards.length,
              itemBuilder: (context, index) => cards[index],
            );
          },
        ),
      ),
    );

I got bad news too though now that the data is updating it exposed some flaws in your logic its duplicating old entries in your array. You'll see. That should be easy to fix though.

来源：https://stackoverflow.com/questions/61111308/streambuilder-in-flutter-stuck-with-connectionstate-waiting-and-displays-only-th