Question

您在下面的PHP和JAVA文件中看到的是一个完整的（虽然简单）注册功能。一切正常。

现在的问题是，

如何检测是否已经使用了用户名字段，以及如何让java方知道这一点，以便我可以给用户一个正确的消息。

ORIGINAL register.php：

<?php

define('HOST','X');
define('USER','X');
define('PASS','X');
define('DB','X');

$con = mysqli_connect(HOST,USER,PASS,DB);

 $name = $_POST['name'];
 $pass = $_POST['pass'];

  $sql = "insert into tbl_user (username,password) values ('$name','$pass')";
  if(mysqli_query($con,$sql)){
    echo 'success';
  }
  else{
    echo 'failure';
  }
  mysqli_close($con);
?>

register.java的一部分：

private void insertToDatabase(String name, String pass) {
    class SendPostReqAsyncTask extends AsyncTask<String, Void, String> {
        @Override
        protected String doInBackground(String... params) {
            String name = params[0];
            String pass = params[1];

        List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
        nameValuePairs.add(new BasicNameValuePair("name", name));
        nameValuePairs.add(new BasicNameValuePair("pass", pass));

        boolean exists = false;


        try {
            HttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(
                    "http://calisapp.esy.es/register.php");
            httpPost.setEntity(new UrlEncodedFormEntity(nameValuePairs));

            HttpResponse response = httpClient.execute(httpPost);

            HttpEntity entity = response.getEntity();


        } catch (ClientProtocolException e) {

        } catch (IOException e) {

        }
        return "";
    }

    @Override
    protected void onPostExecute(String result) {
        super.onPostExecute(result);

        Intent intent = new Intent(Register.this, MainActivity.class);

        startActivity(intent);
        Toast.makeText(Register.this, "Registered successfully", Toast.LENGTH_LONG).show();
        finish();
    }
}
SendPostReqAsyncTask sendPostReqAsyncTask = new SendPostReqAsyncTask();
sendPostReqAsyncTask.execute(name, pass);

}

Answer 1

private void insertToDatabase(String name, String pass) {
class SendPostReqAsyncTask extends AsyncTask<String, Void, String> {
@Override
protected String doInBackground(String... params) {
   String name = params[0];
   String pass = params[1];
   List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
   nameValuePairs.add(new BasicNameValuePair("name", name));
   nameValuePairs.add(new BasicNameValuePair("pass", pass));
   try {
    HttpClient httpClient = new DefaultHttpClient();
    HttpPost httpPost = new HttpPost(                   "http://calisapp.esy.es/register.php");
    httpPost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
    HttpResponse response = httpClient.execute(httpPost);
    InputStream entity = response.getEntity().getContent();
    InputStreamReader inputStream = new InputStreamReader(entity);
    BufferedReader bufferedReader = new BufferedReader(inputStream);
    StringBuilder stringBuilder = new StringBuilder();
    String bufferedStrChunk = null;
    while ((bufferedStrChunk = bufferedReader.readLine()) != null) {
        stringBuilder.append(bufferedStrChunk);
    }
    return stringBuilder.toString();
  } catch (ClientProtocolException e) {
  } catch (IOException e) {
  }
    return "";
}

    @Override
    protected void onPostExecute(String result) {
      super.onPostExecute(result);
      try {
       JSONObject jo = new JSONObject(result);
       String status = jo.getString("status");
       if (status.equals("0")) {
         editTextName.requestFocus();
         editTextName.setError("Username already exists.");
       } else if (status.equals("1")) {
         Intent intent = new Intent(Register.this, MainActivity.class);
         startActivity(intent);
         Toast.makeText(Register.this, "Registered successfully", Toast.LENGTH_LONG).show();
         finish();
       }else if (status.equals("2")) {
         // failed to register
       }
     } catch (JSONException e) {
       e.printStackTrace();
     }
 }
}
 SendPostReqAsyncTask sendPostReqAsyncTask = new SendPostReqAsyncTask();
 sendPostReqAsyncTask.execute(name, pass);

}

Answer 2

try {
    JSONObject jo = new JSONObject(result);
    String status = jo.getString("status");
    if (status.equals("0")) {
      // show the error, username already exists
    } else if (status.equals("1")) {
      // registration successfull
    }else if (status.equals("2")) {
      // failed to register
    }
} catch (JSONException e) {
    e.printStackTrace();
}

在java端，onpostexecute方法中的result参数

sudo apt-get install libcairo2-dev
sudo apt-get install libpango1.0-dev

检测用户名是否已被占用并向该人显示错误消息？

2 个答案: