List names of all documents in subcollection - Firebase Flutter

Question

I am new to Flutter and Firebase. I am trying to get all document Names in a certain collection. Each user has documents which contains todo items.

I already tried it with getting a document snapshot and returning the reference id, but firstly this is a id, not the name, and secondly the id changes on every execution?

Future<String> getLists() async {
    DocumentReference doc_ref = FirebaseFirestore.instance
        .collection('userTodos')
        .doc(userID)
        .collection('lists')
        .doc();
    DocumentSnapshot docSnap = await doc_ref.get();
    return docSnap.reference.id;
  }

I know that it's not possible to get subcollection on mobile apps, but the names of documents should be possible right?

This is how my Firebase looks like:

Firebase Screenshot

I mean, I could create a document which has all document names as items, but this way it would reduce code and would be nicer. Thanks for your help!

UPDATE:

This is my console Output each time the function is called and I print it to the console.

Console Output

Answer 1

I have solved it with trial and error: You have to itterate through all documents and then add the id's to a list:

Future<List> getLists() async {
  List<String> userLists = [];
  CollectionReference col_ref = FirebaseFirestore.instance
      .collection('userTodos')
      .doc(userID)
      .collection('Lists');
  QuerySnapshot docSnap = await col_ref.get();
  docSnap.docs.forEach((elements) {
    userLists.add(elements.id);
  });
  return userLists;
}