在android中创建用户时检查用户名是否可用

Question

I am creating my first android which will take data from a signup form and send it to a php backend.

The php backend will take the data and save in a database and give a jason encoded message telling if it is success or not.

Now I want to eliminate the possibility of dupilicate usernames so when the android app sends data to the php backend I will first check and if it is duplicate I will throw an error message like this

$response["error"] = true;
$response["message"] = "Username Already taken";
echoRespnse(400,$response);

On Success the backend will send something like this

$response["error"] = false;
$response["message"] = "Successfuly Registered";
echoRespnse(201,$response);

How do I enable the android app to read this info and understand if the user was created or an error occured.

My current Android signup.java code looks like this

public void post() throws UnsupportedEncodingException
    {
        // Get user defined values
        uname = username.getText().toString();
        email   = mail.getText().toString();
        password   = pass.getText().toString();
        confirmpass   = cpass.getText().toString();
        phone = phn.getText().toString();

        HttpClient httpclient = new DefaultHttpClient();
        HttpPost httppost = new HttpPost("http://www.rgbpallete.in/led/api/signup");
        if (password.equals(confirmpass)) {
            try {
                List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(4);
                nameValuePairs.add(new BasicNameValuePair("uname", uname));
                nameValuePairs.add(new BasicNameValuePair("pass", password));
                nameValuePairs.add(new BasicNameValuePair("email", email));
                nameValuePairs.add(new BasicNameValuePair("phone", phone));
                httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
                httpclient.execute(httppost);
                //Code to check if user was successfully created
            } catch (ClientProtocolException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        else
        {
            Toast.makeText(getBaseContext(), "Password mismatch", Toast.LENGTH_SHORT).show();
            //Reset password fields
            pass.setText("");
            cpass.setText("");
        }

    }

Answer 1

You could make your "error" an int instead of a boolean, and have your php backend return specific error codes. This would allow your android application to understand the specific error. Without this kind of modification, checking the value of message for a specific string is another option.

For example, you could return 0 if there was no error, 1 if the username was already taken, 2 if .. etc.

Answer 2

I think you want help to get and read the JSON data provided by your service, right? In your SignUp Activity create an AsyncTask because you can not perform this on the main thread.

private class DownloadOperation extends AsyncTask<Void, Void, String> {
    String uname = "";
    String email   = "";
    String password   = "";
    String confirmpass   = "";
    String phone = "";

     @Override
protected void onPreExecute() {
    super.onPreExecute();
    // Get user defined values
    uname = username.getText().toString();
    email   = mail.getText().toString();
    password   = pass.getText().toString();
    confirmpass   = cpass.getText().toString();
    phone = phn.getText().toString();
}

@Override
protected String doInBackground(Void... params) {
        String response = "";
        HttpClient httpclient = new DefaultHttpClient();
        HttpPost httppost = new HttpPost("http://www.rgbpallete.in/led/api/signup");
        HttpEntity httpEntity = null;
        HttpResponse httpResponse = null;
        try {
            List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(4);
            nameValuePairs.add(new BasicNameValuePair("uname", uname));
            nameValuePairs.add(new BasicNameValuePair("pass", password));
            nameValuePairs.add(new BasicNameValuePair("email", email));
            nameValuePairs.add(new BasicNameValuePair("phone", phone));
            httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
            httpclient.execute(httppost);
            httpResponse = httpClient.execute(httpPost);
        } catch (ClientProtocolException e) {
            e.printStackTrace();
            } catch (IOException e) {
            e.printStackTrace();
        }
        httpEntity = httpResponse.getEntity();
        response = EntityUtils.toString(httpEntity);
        return response;
}

@Override
protected void onPostExecute(String result) {
    super.onPostExecute(result);
    Log.d("tag", "Result:\n" + result);
}}

And then call

// Calling async task to get json
new DownloadOperation().execute();

And you will see the json string printed on your Console :)

To get an JSONObject using the response String:

JSONObject jsonObj = new JSONObject(STRING);

Hope that helps.

Answer 3

BEFORE registering the user and inserting into database ,check the query for username in database..and if user name found then encode json value as error

$query=mysql_query("select id from yourtable where username ='$username'"); If(mysql_numnum_rows($query)>0)

 // example for response //responses from server for success response["success"]=1; response["message"]='No error code' //responses from server for duplicate username response["success"]==0 response["message"]='Username exists'; // java code // after getting string from server parse in into json object JSONObject jsonObj = new JSONObject(STRING); int success = jsonObj.getInt("success"); message = jsonObj.getString("message"); if (success == 1) { // register successfully } else { // username already exist }