Unhandled Exception: type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'List<dynamic>?' in type cast

Question

I am getting the data from firestore and storing the data as List, Since the data from the firestore is map i couldn't save it correctly and i am getting this error.

my code.

getData() async{

final dataDB = await FirebaseFirestore.instance.collection('TransactionData').doc(getUid()).get();
    snapshot = dataDB;
    final Map documentData = snapshot.data() as Map;

    _cards = documentData as List?;

    setState(() {
      _data = _cards![0];
    });
  }

my data from Firestore.

{21Aug5298Sav: [{categoryName: Education, uid: LNM6JQuoKCPIANTyQHMKWLIzl5m1, amount: 3,000.00, lastUpdatedDate: 25-08-2022, createdDate: 25-08-2022, toAccountId: , type: Credit, transfer: N, accountId: 21Aug5298Sav, auto: Y, accountName: null, transactionId: deb1621, categoryLogo: assets/images/Education.png, untagged: N, categoryBackgroundColor: 0xffFFA2C0, currency: INR, transactionDate: 25-08-2022}, {categoryName: Education, uid: LNM6JQuoKCPIANTyQHMKWLIzl5m1, amount: 300.00, lastUpdatedDate: 25-08-2022, createdDate: 25-08-2022, toAccountId: , type: Debit, transfer: N, accountId: 21Aug5298Sav, auto: Y, accountName: null, transactionId: deb5366, categoryLogo: assets/images/Education.png, untagged: N, categoryBackgroundColor: 0xffFFA2C0, currency: INR, transactionDate: 25-08-2022}, {categoryName: Travelling, uid: LNM6JQuoKCPIANTyQHMKWLIzl5m1, amount: 100.00, lastUpdatedDate: 24-08-2022, createdDate: 24-08-2022, toAccountId: , type: , transfer: N, accountId: 21Aug5298Sav, a<…>

i just want the list to contain all the data which was retrieved from the firestore. Can someone please help me on this.

Thanks in advance.

Answer 1

In the codes you had tried to cast a map as a list and assign it to the_cards variable. Try this

final Map documentData = snapshot.data() as Map;

_cards = documentData.values.toList();
//Or

_cards = documentData.values.toList().first;

Edit

var allDocData = documentData.values.toList();

for(int i= 0; i < allDocData.length; i++)
 {
   _cards.add(allDocData[i]);
}

Answer 2

You cant cast a Map to a List. Thats you error. If you check your data, you will see that is not a List, it's a Map. If you want the list inside, you will need to access through the key "21Aug5298Sav"

Ex.

List _cards = documentData["21Aug5298Sav"]

Answer 3

try this:

Map data = snapshot.data() as Map;
var firestoreResult = documentData.values.toList();
var finalResult = [];
for (var item in firestoreResult) {
  for (var x in item) {
     finalResult = [...finalResult, ...x];
  }
}

and use it like this:

setState(() {
   _data = finalResult![0];
});

Answer 4

I have changed the Data structure of my firestore data and its working perfectly. Thanks guys for your valuable time.