无法从Firebase数据库获取用户名

我的应用正在根据以下代码发送用户名

  mAuth.createUserWithEmailAndPassword(email,password).addOnCompleteListener(new 
  OnCompleteListener<AuthResult>() {
                @Override
                public void onComplete(@NonNull Task<AuthResult> task) {
                    if (task.isSuccessful()){


                        currentUserUid=mAuth.getCurrentUser().getUid();
                        FirebaseDatabase database = FirebaseDatabase.getInstance();
                        DatabaseReference myRef = database.getReference("MyUserList");
                        
  myRef.child(usernameInput).child(currentUserUid).child("username").setValue(usernameInput);

                        sendUserToLoginActivity();
                        Toast.makeText(RegisterActivity.this, "Account Created Successfully", 
  Toast.LENGTH_SHORT).show();
                        loadingBar.dismiss();

                    }

现在，我必须在另一个活动中从Firebase数据库获取用户名。我尝试了下面的方法，但是每次'score'传递给数据库，而不传递给username时。我不想更改用户名设置方式（以上代码），因为我正在检查用户注册时重复的用户名。我如何获得当前的用户名？

  private String currentUserUid;
  private FirebaseAuth mAuth;
  private String name;



  public void finisHere(){

       
        FirebaseDatabase database = FirebaseDatabase.getInstance();
        DatabaseReference myRef = database.getReference("Score");
         String key=myRef.push().getKey();

        //......................
        currentUserUid= mAuth.getCurrentUser().getUid();

        DatabaseReference cUserNameRef = database.getReference("MyUserList");

        cUserNameRef.child(currentUserUid).addListenerForSingleValueEvent(new 
 ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot snapshot) {
                for (DataSnapshot dataSnapshot:snapshot.getChildren()){
                   // String name="";
                    name=dataSnapshot.child("username").getValue(String.class);

                }
            }

            @Override
            public void onCancelled(@NonNull DatabaseError error) {

            }
        });
        savingScoreModel scoreModel=new savingScoreModel(score,name);
        myRef.child(key).setValue(scoreModel);
        Intent intent =new 
        Intent(liveQuestionActivity.this,MainActivity.class);

        Toast.makeText(this, currentUserUid, Toast.LENGTH_SHORT).show(); //Toast is working
        startActivity(intent);
        finishAffinity();


    }

我正在通过以下代码验证重复的用户名。

  private  void DuplicateUserName(){
        final DatabaseReference rootRef = 
 FirebaseDatabase.getInstance().getReference();
        DatabaseReference userNameRef = 
 rootRef.child("MyUserList").child(usernameInput);
        ValueEventListener eventListener = new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {

                if(!dataSnapshot.exists()) {
                    //create new user
                    //Toast.makeText(RegisterActivity.this, "success", 
 Toast.LENGTH_SHORT).show();
                   /* FirebaseDatabase database = 
 FirebaseDatabase.getInstance();
                    DatabaseReference myRef = 
 database.getReference("MyUserList");
                    
 myRef.child(usernameInput).child("username").setValue(usernameInput);

                    */
                    CreateNewAccount();


                }
                else {
                    UserName.setError("This username already taken");
                    UserName.requestFocus();
                    loadingBar.dismiss();
                }


            }

            @Override
            public void onCancelled(DatabaseError databaseError) {
                Toast.makeText(RegisterActivity.this, 
databaseError.getMessage(), Toast.LENGTH_SHORT).show();
            }
        };
        userNameRef.addListenerForSingleValueEvent(eventListener);
    }