Question

嗨，Android开发新手，请在此选择一个用户名活动，我想要app来检查firebase数据库中是否存在用户名，如果为true，则显示对话框并且不向数据库添加值，如果为false add。到目前为止，如果它是真的，它继续添加到firebase数据库..我做错了什么？

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_check);
        mAuth = FirebaseAuth.getInstance();


        pd = new ProgressDialog(this);
        FirebaseUser curr_user = FirebaseAuth.getInstance().getCurrentUser();
        String uid = null;
        if (curr_user != null) {
            uid = curr_user.getUid();

            mDatabase = FirebaseDatabase.getInstance().getReference().child("Users").child(uid);


            cUser = (TextInputLayout) findViewById(R.id.cUserr);
            cBut = (Button) findViewById(R.id.cCon);

            TextView backArrow = (TextView) findViewById(R.id.home);
            backArrow.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Intent mainintent = new Intent(CheckUsername.this, MainActivity.class);
                    mainintent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK);
                    startActivity(mainintent);
                    finish();
                }
            });

这里我调用了检查用户名是否存在方法

            cBut.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Log.d(TAG, "onClick: attempting to save changes.");
                    checkIfUsernameExists("");


                }
            });
        }
    }


    private void saveProfileSettings() {


        final String username = cUser.getEditText().toString();


        //case1: if the user made a change to their username
        if (TextUtils.isEmpty(username)) {
            cUser.setError("Empty Field");
        } else {
//            checkIfUsernameExists(username);
        }
    }

这里我检查是否存在，如果是真正的呼叫提醒对话但似乎不是todo，它所做的只是创建数据库中的值（如果它存在）

    private void checkIfUsernameExists(final String username) {
        Log.d(TAG, "checkIfUsernameExists: Checking if  " + username + " already exists.");

        DatabaseReference reference = FirebaseDatabase.getInstance().getReference();
        Query query = reference
                .child(getString(R.string.dbname_users))
                .orderByChild(getString(R.string.field_username))
                .equalTo(username);
        query.addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                if (dataSnapshot.exists()) {
                    //add the username
                    updateUsername(username);
                    Toast.makeText(CheckUsername.this, "saved username.", Toast.LENGTH_SHORT).show();

                }
                for (DataSnapshot singleSnapshot : dataSnapshot.getChildren()) {
                    if (!singleSnapshot.exists()) {
                        Log.d(TAG, "checkIfUsernameExists: FOUND A MATCH: " + singleSnapshot.getValue(Users.class).getName());
                        request_code();
                        Toast.makeText(CheckUsername.this, "That username already exists.", Toast.LENGTH_SHORT).show();
                    }
                }
            }



                @Override
            public void onCancelled(DatabaseError databaseError) {

            }

这是在check username方法中调用的警告对话框方法，但它似乎不起作用。

    public void request_code(){

        AlertDialog.Builder alert = new AlertDialog.Builder(this);
        alert.setTitle("Pls Enter a Different Username");

        alert.setPositiveButton("OK", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialogInterface, int i) {

            }
        });

        alert.show();
    }

    }

Answer 1

如果你使USERNAME是唯一的，那么我想只是

DatabaseReference reference = FirebaseDatabase.getInstance().getReference();
    Query query = reference
            .child(getString(R.string.dbname_users))
            .orderByChild(getString(R.string.field_username))
            .equalTo(username);
    query.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            if (dataSnapshot.exists()) {
                //add the username
                updateUsername(username);
                Toast.makeText(CheckUsername.this, "saved username.", Toast.LENGTH_SHORT).show();

            }
        else
           {
                                  request_code();

             }


            }
        }

Firebase查询以在添加之前检查值是否存在，如果为true，则不进行添加，如果为false则添加

1 个答案: