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']);
      },
      one rror: (e) => print("Error getting document: $e"),
    );
    return Spinner(text: "Unable to retrieve data");
  }

}  

Here's the corresponding Firebase database screenshot

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?

CodePudding user response：

Did you initialize the Firebase Instance?

await Firebase.initializeApp()

CodePudding user response：

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...")
      }    
    }    
  )
}