Question 118977 in Firebase Question posted in
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Firebase – FutureBuilder in DART : "The method 'data' can't be unconditionally invoked because the receiver can be 'null'. Try making the call…"

It’s been a few days now that I’m working on a flutter code by following tutorials to learn how to use Firebase with it. Nevertheless I completely block on a step that the person manages to realize, I have however copied the code at 100% and here is the error that I have:

The method 'data' can't be unconditionally invoked because the receiver can be 'null'. Try making the call conditional (using '?.') or adding a null check to the target ('!').

Here is the code:

class GetUserData extends StatelessWidget {
  final String documentId;
  final String fieldName;
  final String fieldTitle;

  GetUserData(
      {super.key,
      required this.documentId,
      required this.fieldName,
      required this.fieldTitle});

  @override
  Widget build(BuildContext context) {
    CollectionReference users = firestore.collection('Users');
    return FutureBuilder(
        future: users.doc(documentId).get(),
        builder:
            (BuildContext context, AsyncSnapshot<DocumentSnapshot> snapshot) {
            Map<String, dynamic> data = snapshot.data.data();
          return ListTile(
            title: Text(data[fieldName]),
            subtitle: Text(data[fieldTitle]),
          );
        });
  }
}

I’ve tried many things:

Map<String, dynamic> data = snapshot.data!.data();

return FutureBuilder( future: users.doc(documentId).get(), builder: (BuildContext context, AsyncSnapshot<DocumentSnapshot> snapshot) { Map<String, dynamic> data = snapshot.data!.data() as Map<String, dynamic>; return ListTile( title: Text(data[fieldName]), subtitle: Text(data[fieldTitle]), ); });

Here I don’t have the error but a crash when I debug with _CastError (Null check operator used on a null value)

I have looked everywhere and I don’t understand how to solve this,

Thank you so much for your help,

Tags:

2

Answers


  1. 0

    try to handle all condition

    @override
  Widget build(BuildContext context) {
    CollectionReference users = firestore.collection('Users');
    return FutureBuilder(
        future: users.doc(documentId).get(),
        builder:
            (BuildContext context, AsyncSnapshot<DocumentSnapshot> snapshot) {
           /// success fetch data
          if(snapshot.hasData){
           Map<String, dynamic> data = jsonDecode(snapshot.data);
           return ListTile(
            title: Text(data[fieldName]),
            subtitle: Text(data[fieldTitle]),
          );
          }
         /// failed and throw error
          else if(snapshot.hasError){
            return Text('${snapshot.error}');
          } 
        /// loading condition
        else {
        return Center(child:CircularProggressIndicator());
         }
        });
  }
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  2. 0

    You are not decoding the response from the firebase properly, try considering the below code:

     @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
          child: FutureBuilder<DocumentSnapshot<Map<String, dynamic>>>(
        future: FirebaseFirestore.instance
            .collection('users')
            .doc(documentId) 
            .get(),
        builder: (_, snapshot) {
          if (snapshot.hasError) return Text('Error = ${snapshot.error}');
          if (snapshot.connectionState == ConnectionState.waiting) {
            return const Text("Loading");
          }
          Map<String, dynamic> data = snapshot.data!.data()!;
          return Text(data['fieldName']); // give your valid data here
        },
      )),
    );
  }
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