How to display another widget if the collection is empty?-CodePudding

I have a collection A in cloud Firestore which is empty for now but later it will be filled, I want to display a widget like Text("No Data") when there is no data in it. This is my code

class Green extends StatefulWidget {
  const Green({Key? key}) : super(key: key);

  @override
  State<Green> createState() => _GreenState();
}

class _GreenState extends State<Green> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        body: StreamBuilder<QuerySnapshot<Map<String, dynamic>>>(
      stream: FirebaseFirestore.instance
          .collection(uid)
          .where("gatename", isEqualTo: "A")
          .snapshots(),
      builder: (_, snapshot2) {
        if (snapshot2.hasError) return Text('Error = ${snapshot2.error}');

        if (snapshot2.hasData) {
          final ds = snapshot2.data!.docs;
          return Padding(
            padding: const EdgeInsets.all(38.0),
            child: Container(
              height: 600,
              child: ListView.builder(
                itemCount: ds.length,
                itemBuilder: (_, i) {
                  final d = ds[i].data();
                  return ListTile(
                    title: Text(d["time"].toString()),
                    leading: Text(d["gatename"].toString()),
                  );
                },
              ),
            ),
          );
        }
        return const Center(child: CircularProgressIndicator());
      },
    ));
  }
}

I have used else if (snapshot.data!.docs.isEmpty){} but it is still showing white screen.

CodePudding user response：

`if(snapshot.hasData && snapshot.data.isEmpty)` - this case can be worked.

CodePudding user response：

You can check the data you've received

if (snapshot2.hasData) {
  if (snapshot2.data==null || snapshot2.data.isEmpty) {
    return Text('No Data');
  } else {
    final ds = snapshot2.data!.docs;
    return Padding(
      padding: const EdgeInsets.all(38.0),
      child: Container(
        height: 600,
        child: ListView.builder(
          itemCount: ds.length,
          itemBuilder: (_, i) {
            final d = ds[i].data();
            return ListTile(
              title: Text(d["time"].toString()),
              leading: Text(d["gatename"].toString()),
            );
          },
        ),
      ),
    );
  }
}

CodePudding user response：

Currently you are just checking if the data existing and not if it's empty.

You should also check if the data is empty:

if (snapshot2.hasData && snapshot2.data == null) {
   return widget1
} else {
   return widget2
}

Cleaner way of doing if else in dart:

snapshot2.hasData && snapshot2.data == null
   ? widget1
   : widget2