How get each element of an array in firestore

Question

I've been spending so much hours searching on how to get an array inside. I want to access each the element of an array and store it in a string like for example, String array =??? (I want to get the value).

To further understand my question. Let's say I have an array that contains all id and I want to check if there's an id existing and if so I want to make each element to be stored in a string (each element must be on different string) so I can use it later in my other activities.

Is there a way like using for loop?

String userId = FirebaseAuth.getInstance().getCurrentUser().getUid();

        DocumentReference docRef = db.collection("Users").document(userId);


        docRef.get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
            @Override
            public void onComplete(@NonNull Task<DocumentSnapshot> task) {
                if (task.isSuccessful()) {
                    DocumentSnapshot document = task.getResult();
                    if (document.exists()) {
                        String plan_id =  document.get("plan_id").toString();
                        Log.d(TAG, "***Found field: " + plan_id);
                    } else {
                        Log.d(TAG, "***No such document");
                    }
                } else {
                    Log.d(TAG, "***Get failed with ", task.getException());
                }
            }
        });

I get the following output

***Found field: [3bTzKOmIS1zEHprJa1u0, 6nDgyEimKOnoPbZRsbmQ]

Answer 1

If you have a list type field in a document, it will be converted to a List type object in Java when you fetch it. What you're doing now is converting that List to a String, which is not very helpful. Just cast it to a List and iterate it like any other List:

List<Object> plan_id = (List<Object>) document.get("plan_id");
for (Object o : plan_id) {
    Log.d(TAG, "List element " + o.toString());
}