How to make a for each URLs with Url_Launcher?

Question

I wanted to make a looping URL with firebase. I use this fucntion to get the url from my firebase.

class getUri extends StatelessWidget {

  final String documentId;

  getUri({required this.documentId});

  @override
  Widget build(BuildContext context) {

    //get collection
    CollectionReference umum = FirebaseFirestore.instance.collection('umum');

    return FutureBuilder<DocumentSnapshot>(
      future: umum.doc(documentId).get(),
        builder: ((context, snapshot){
      if(snapshot.connectionState==ConnectionState.done){
        Map<String, dynamic> data = snapshot.data!.data() as Map<String, dynamic>;
        return Text('${data['url']}');
      }
      return Text('loading...');
    }
    )
    );
  }
}

but I can't get it to run on my code

Expanded(
                child: FutureBuilder(
                  future: umum(),
                    builder: (context, snapshot) {
                  return ListView.builder(
                      itemCount: docID.length,
                      itemBuilder: (context, index) {
                        return ListTile(
                          title: Text(docID[index]),
                          onTap: () {
                            launchUrl(
                                Uri.parse(getUri(documentId: docId[index])),
                                mode: LaunchMode.externalApplication
                            );
                          },
                        );
                      }
                  );
                }
                )
            )

The error said "Error: The argument type 'getUri' can't be assigned to the parameter type 'String'"

I tried adding cast on the getUri but it gave me this error "The following _CastError was thrown while handling a gesture: type 'getUri' is not a subtype of type 'String' in type cast"

Uri.parse(getUri(documentId: docID[index]) as String)

Answer 1

You are defining getUri as a StatelessWidget, not function. To define getUri as a function, do it like this:

Future<String> getUri({required String documentId}) async {
  final umum = FirebaseFirestore.instance.collection('umum');
  final snapshot = await umum.doc(documentId).get();
  Map<String, dynamic> data = snapshot.data() as Map<String, dynamic>;
  return data['url'];
}

You can then use the function like this:

onTap: () async {
  launchUrl(
    Uri.parse(await getUri(documentId: docId[index])), // use await keyword here
    mode: LaunchMode.externalApplication
  );
}

This should fix the problems to your code. However, I recommend following the usage instructions from the Firestore official documentation, and add a proper error handling as well.