检查用户是否存在于Firestore中 [英] Check if user exists in Firestore

问题描述

我想在Cloud Firestore中创建一个用户数据库，并将电子邮件作为每个用户的唯一ID。用户应该在集合中，每个用户都是文档。

这是我如何检查用户是否存在于登录活动中：

  FirebaseFirestore db = FirebaseFirestore.getInstance（）; 
 final DocumentReference userRef = db.collection（users）。document（email）; 
 userRef.get（）。addOnCompleteListener（new OnCompleteListener< DocumentSnapshot>（）{
 @Override $ b $ public void onComplete（@NonNull Task< DocumentSnapshot> task）{
 if .isSuccessful（））{
 DocumentSnapshot document = task.getResult（）; 
 $ b toast.makeText（LoginActivity.this，task.getResult（）。toString（），
 Toast .LENGTH_SHORT）.show（）; 
 
 if（document！= null）{
 //用户存在... 
} 
 
 
 else {
 //用户不存在... 
 } 
 
 
 
 else 
 connectionErrorActivity（）; 
 
} 
}）; 
  

数据库为空，如您所见：

方法。 c> getData 来获取它的内容。

I'd like to create a users database in Cloud Firestore, with the email as the unique ID for each user. The users should be in a collection, and each user is a document.

This is how I check if the user exists in the login activity:

FirebaseFirestore db = FirebaseFirestore.getInstance();
                            final DocumentReference userRef = db.collection("users").document(email);
                            userRef.get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
                                @Override
                                public void onComplete(@NonNull Task<DocumentSnapshot> task) {
                                    if (task.isSuccessful()) {
                                        DocumentSnapshot document = task.getResult();

                                        Toast.makeText(LoginActivity.this, task.getResult().toString(),
                                                Toast.LENGTH_SHORT).show();

                                        if (document != null) {
                                            //The user exists...
                                        }


                                        else {
                                            //The user doesn't exist...
                                           }

                                        }
                                    }
                                    else
                                        connectionErrorActivity();

                                }
                            });

The database is empty, as you can see:

My problem is, that document is never null, even tough the database is empty. The toast shows that the string value of document is: COM.GOOGLE.FIREBASE.FIRESTORE.DOCUMENTSNAPSHOT@8ED6B96.

Is this the correct way to do this? What can I do to fix it?

解决方案

The result of this Task is a DocumentSnapshot. Whether or not the underlying document actually exists is available via the exists method.

If the document does exist you can call getData to get at the contents of it.

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