Firestore firebase Android search and update query

Question

I am trying to update a field of existing document in my collection in FireBase Firestore. I want to search that document using one of its field. My collec

Answer 1

To solve this, please use the following lines of code:

FirebaseFirestore rootRef = FirebaseFirestore.getInstance();
CollectionReference complaintsRef = rootRef.collection("complaints");
complaintsRef.whereEqualTo("id", 5).get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
    @Override
    public void onComplete(@NonNull Task<QuerySnapshot> task) {
        if (task.isSuccessful()) {
            for (QueryDocumentSnapshot document : task.getResult()) {
                Map<Object, String> map = new HashMap<>();
                map.put("complainant_Name", "ABC");
                complaintsRef.document(document.getId()).set(map, SetOptions.merge());
            }
        }
    }
});

After using this code, the property complainant_Name will hold the value of ABC.