CODEWITHSUNDEEP
flutterfirebasedartgoogle-cloud-firestore
user6123723
user6123723

Reputation: 11106

Unable to query data from Firebase

I'm trying to retrieve data from Firebase. Here's my code snippet

Future main() async {

  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();

  // DatabaseReference ref = FirebaseDatabase.instance.ref();
  runApp(const MyApp());
}
class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    final docRef = FirebaseFirestore.instance.collection('data').doc("rules");
    docRef.get().then(
          (DocumentSnapshot doc) {
        final data = doc.data() as Map<String, dynamic>;
        return MyHomePage(title: 'ARNET Helper',
            rules: data['ruleslist']);
      },
      onError: (e) => print("Error getting document: $e"),
    );
    return Spinner(text: "Unable to retrieve data");
  }

}

Here's the corresponding Firebase database screenshot enter image description here

I do have the google-services.json added to the android/app folder. But with the above snippet, lines from the "then" block don't seem to get hit and the spinner (i.e return Spinner(text: "Unable to retrieve data");) is always returned.

I do have these lines added to AndroidManifest.xml

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.INTERNET"/>

I tried to debug it. But the breakpoint at line 46 is never hit. Instead the execution goes straight to line 52. What am I missing? enter image description here

I've even tried using FutureBuilder as suggested by one of the commenters. I always get "Something went wrong.." spinner

  @override
  Widget build(BuildContext context) {
    CollectionReference data = FirebaseFirestore.instance.collection('data');
    return FutureBuilder<DocumentSnapshot>(
      future:  data.doc('rules').get(),
      builder:
          (BuildContext context, AsyncSnapshot<DocumentSnapshot> snapshot) {

        if (snapshot.hasError) {
          return Spinner(text: 'Something went wrong...');
        }

        if (snapshot.hasData && !snapshot.data!.exists) {
          return Spinner(text: 'Document does not exist...');
        }


        if (snapshot.connectionState == ConnectionState.done) {
          Map<String, dynamic> data = snapshot.data! as Map<String, dynamic>;

          return MyHomePage(title: 'ARNET Helper', rules: data['ruleslist'].entries.toList() as List<dynamic>);
        }

        return Spinner(text: 'Loading...');
      },
    );
  }
}

Upvotes: 0

Views: 122

Answers (3)

user6123723
user6123723

Reputation: 11106

Not sure what the issue was but the config below worked.

pubspec.yaml

  firebase_core: ^1.24.0
  cloud_firestore: ^3.5.0

FutureBuilder query

@override
  Widget build(BuildContext context) {
    CollectionReference data = FirebaseFirestore.instance.collection('data');
    return FutureBuilder<DocumentSnapshot>(
      future:  data.doc("rules").get(),
      builder:
          (BuildContext context, AsyncSnapshot<DocumentSnapshot> snapshot) {

        if (snapshot.hasError) {
          return Spinner(text: 'Something went wrong...');
        }

        if (snapshot.hasData && !snapshot.data!.exists) {
          return Spinner(text: 'Document does not exist...');
        }


        if (snapshot.connectionState == ConnectionState.done) {
          final data = snapshot.data!.get('ruleslist') ;

          return MyHomePage(title: 'ARNET Helper', rules: data);
        }

        return Spinner(text: 'Loading...');
      },
    );
  }
}

Upvotes: 0

Frank van Puffelen
Frank van Puffelen

Reputation: 598765

The problem is that get() is an asynchronous operation, and you can't return widgets asynchronously in build.

The simplest way to fix this is to use a FutureBuilder:

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  return FutureBuilder<String>(
    future: FirebaseFirestore.instance.collection('data').doc("rules").get(),
    builder: (BuildContext context, AsyncSnapshot<DocumentSnapshot> asyncSnapshot) {
      if (snapshot.hasData) {
        final data = asyncSnapshot.data!.data() as Map<String, dynamic>;
        return MyHomePage(title: 'ARNET Helper', rules: data['ruleslist']);
      }
      else if (snapshot.hasError) {
        return Text("Error: ${snapshot.error}")
      } 
      else {
        return Text("Loading user data...")
      }    
    }    
  )
}

Upvotes: 1

Leonardo Rosa
Leonardo Rosa

Reputation: 168

Did you initialize the Firebase Instance?

await Firebase.initializeApp()

Upvotes: 0

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