[英]How to check through Firebase Firestore that such a name already exists? - Java
要检查名称“Creator”是否已被占用,请使用以下代码行:
FirebaseFirestore rootRef = FirebaseFirestore.getInstance();
CollectionReference usersRef = rootRef.collection("users");
Query userNameQuery = usersRef.whereEqualTo("name", "Creator");
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("name");
Log.d(TAG, userName + " already exists.");
} else {
Log.d(TAG, userName + " doesn't exist.");
}
}
} else {
Log.d("TAG", "Error getting documents: ", task.getException().getMessage());
}
}
});
由于您的屏幕截图显示“创建者”已被拍摄,因此 logcat 中的结果将是:
Creator already exists.
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