通过数据库查询用户名以确保当用户想要更改其现有用户名时不存在相同的用户名

Question

What I am trying to do is when a user decides to edit their username I would like to run a query through the database making sure that that username which they pick hasn't been taken. For the most part, I think I have it right, I run a for loop to look through all of the usernames that have been added to the database, and if one matches it shows A Toast message.

The issue is it shows the Toast message, but still changes the username even if it's in use. I know it's simple code, but I can't figure out what I am doing wrong. Someone mind having a look? I think the issue is the mUsername , because I set it in the updateProfile(); method, but if I set the new mUserName1 , well I can't because it's an EditText and not a String .

EditProfileActivity

public class EditProfileActivity extends AppCompatActivity {

    ImageView mClose, mCheckmark, mImageProfile;
    TextView mChangePhoto;
    MaterialEditText mName, mUsername, mBio;

    private String mUsername1;
    private String mUsername2;

    FirebaseUser mFirebaseUser;

    private Uri mImageUri;
    StorageReference mStorageReference;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_edit_profile);

        mClose = findViewById(R.id.close);
        mCheckmark = findViewById(R.id.post_checkmark);
        mImageProfile = findViewById(R.id.image_profile);
        mChangePhoto = findViewById(R.id.text_view_change_profile_picture);
        mName = findViewById(R.id.fullname);
        mUsername = findViewById(R.id.username);
        mBio = findViewById(R.id.bio);

        mFirebaseUser = FirebaseAuth.getInstance().getCurrentUser();
        mStorageReference = FirebaseStorage.getInstance().getReference("uploads");

        DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Users").child(mFirebaseUser.getUid());
        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                User user = dataSnapshot.getValue(User.class);
                if (user != null) {
                    mName.setText(user.getFullname());
                    mUsername.setText(user.getUsername().toLowerCase());
                    mBio.setText(user.getBio());
                    Glide.with(getApplicationContext()).load(user.getImageurl()).into(mImageProfile);
                }
            }

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

            }
        });

        mClose.setOnClickListener(v -> new AlertDialog.Builder(EditProfileActivity.this)
                .setMessage("Exit without saving changes?")
                .setPositiveButton("Yes", (dialog, which) -> {
                    finish();
                }).setNegativeButton("No", null).show());

        mChangePhoto.setOnClickListener(v -> CropImage.activity()
                .setAspectRatio(1, 1)
                .setCropShape(CropImageView.CropShape.OVAL)
                .start(EditProfileActivity.this));

        mImageProfile.setOnClickListener(v -> CropImage.activity()
                .setAspectRatio(1, 1)
                .setCropShape(CropImageView.CropShape.OVAL)
                .start(EditProfileActivity.this));

        mCheckmark.setOnClickListener(v -> {

            String str_name = mName.getText().toString();
            String str_username = mUsername.getText().toString();
            String str_bio = mBio.getText().toString();

            if (TextUtils.isEmpty(str_username) || TextUtils.isEmpty(str_bio) || TextUtils.isEmpty(str_name)) {
                Toast.makeText(this, "Please fill in all fields", Toast.LENGTH_SHORT).show();
            } else if (str_username.length() > 20) {
                Toast.makeText(this, "Username cannot contain more than 20 characters", Toast.LENGTH_SHORT).show();
            } else {
                updateProfile(mName.getText().toString(), mUsername.getText().toString().toLowerCase(), mBio.getText().toString());
            }
        });
    }

    private void updateProfile(String fullname, String username, String bio) {
    DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Users").child(mFirebaseUser.getUid());

        mUsername1 = username.replaceAll("\\s+", "");
        mUsername1 = username.replaceAll("[^\\w]", "");

        DatabaseReference reference1 = FirebaseDatabase.getInstance().getReference("Users");
        reference1.addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                    User user = snapshot.getValue(User.class);
                    if (user != null) {
                        if (user.getUsername().equals(mUsername1)) {
                            Toast.makeText(EditProfileActivity.this, "That username is already in use", Toast.LENGTH_SHORT).show();
                        } else {
                            HashMap<String, Object> hashMap = new HashMap<>();
                            hashMap.put("fullname", fullname);
                            hashMap.put("username", mUsername1.toLowerCase());
                            hashMap.put("bio", bio);

                            reference.updateChildren(hashMap);
                        }
                    }
                }
            }

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

            }
        });
    }

Answer 1

Add a break statement after the toast message. As you loop around a list of user objects from the data snapshot. Also, You need to search for all the user object before saving.

 if (user.getUsername().equals(mUsername1)) {
                        Toast.makeText(EditProfileActivity.this, "That username is already in use", Toast.LENGTH_SHORT).show();
break;
                    }

Updates code -

       DatabaseReference reference1 = FirebaseDatabase.getInstance().getReference("Users");
            reference1.addListenerForSingleValueEvent(new ValueEventListener() {
                @Override
                public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
      boolean ifUserNameExist = false;
                    for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                        User user = snapshot.getValue(User.class);
                        if (user != null) {
                            if (user.getUsername().equals(mUsername1)) {
                                Toast.makeText(EditProfileActivity.this, "That username is already in use", Toast.LENGTH_SHORT).show();
                           ifUserNameExist = true;
                            } 
                        }
                    }
if(!ifUserNameExist){
   HashMap<String, Object> hashMap = new HashMap<>();
                                hashMap.put("fullname", fullname);
                                hashMap.put("username", mUsername1.toLowerCase());
                                hashMap.put("bio", bio);

                                reference1.updateChildren(hashMap);
}
                }

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

                }
            });