Firestore query - checking if username already exists
Solution 1:
The following query returns all users with provided usernameToCheck. If username is unique then youll get only one documentSnapShot.
Query mQuery = mFirebaseFirestore.collection("all_users")
.whereEqualTo("username", "usernameToCheck");
mQuery.addSnapshotListener(new EventListener<QuerySnapshot>() {
@Override
public void onEvent(QuerySnapshot documentSnapshots, FirebaseFirestoreException e) {
for (DocumentSnapshot ds: documentSnapshots){
if (ds!=null){
String userName = document.getString("username");
Log.d(TAG, "checkingIfusernameExist: FOUND A MATCH: " +userName );
Toast.makeText(getActivity(), "That username already exists.", Toast.LENGTH_SHORT).show();
}
}
}
});
Solution 2:
To solve this, please use the following lines of code:
FirebaseFirestore rootRef = FirebaseFirestore.getInstance();
CollectionReference allUsersRef = rootRef.collection("all_users");
Query userNameQuery = allUsersRef.whereEqualTo("username", "userNameToCompare");
userNameQuery.get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
@Override
public void onComplete(@NonNull Task<QuerySnapshot> task) {
if (task.isSuccessful()) {
for (DocumentSnapshot document : task.getResult()) {
if (document.exists()) {
String userName = document.getString("username");
Log.d(TAG, "username already exists");
} else {
Log.d(TAG, "username does not exists");
}
}
} else {
Log.d("TAG", "Error getting documents: ", task.getException());
}
}
});
In which userNameToCompare
is of type String and is the user name of the user with which you want to make the comparison.