将Android连接到MySQL

Question

So I'm really new to this. I was following a tutorial on web that showed how to connect these two. But everything I do it just jumps to catch part and it says "No connection". What am I missing? I also connect to a http server to use a PHP script which queries username and password from the database.

try
    {
        nameValuePairs = new ArrayList<NameValuePair>();

        nameValuePairs.add(new BasicNameValuePair("username", username));
        nameValuePairs.add(new BasicNameValuePair("password", password));

        httpPost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
        response = httpClient.execute(httpPost);

        if(response.getStatusLine().getStatusCode()==200)
        {
            entity = response.getEntity();

            if(entity != null)
            {
                InputStream instream = entity.getContent();

                JSONObject jsonResponse = new JSONObject(instream.toString());

                String retUser = jsonResponse.getString("upime");
                String retPass = jsonResponse.getString("geslo");

                if(username.equals(retUser) && password.equals(retPass))
                {
                    SharedPreferences sp = getSharedPreferences("logindetails", 0);

                    SharedPreferences.Editor spedit = sp.edit();

                    spedit.putString("upime", username);
                    spedit.putString("geslo", password);

                    spedit.commit();

                    Toast.makeText(getBaseContext(), "Login successful", Toast.LENGTH_SHORT).show();
                }
                else
                {
                    Toast.makeText(getBaseContext(), "Failed to login", Toast.LENGTH_SHORT).show();
                }
            }
        }
    } catch (Exception e) {
        e.printStackTrace();
        Toast.makeText(getBaseContext(), "No connection", Toast.LENGTH_LONG).show();
    }

Answer 1

 <?php 
 header('Content-Type: application/json'); 
 $dbhost ="localhost"; 
 $dbuser = "username"; 
 $dbpass = "password"; 
 $dbdb = "db"; 
 $connect = mysql_connect($db_host, $dbuser, $dbpass) or die("connection error"); 

 mysql_select_db($dbdb);
 $username =$_POST['username'];
 $password=$_POST['password'];
 $query = mysql_query("SELECT * FROM users WHERE user='$username' AND pass='$password'");

  $num = mysql_num_rows($query);
 if($num == 1) 
{ 
 while($list=mysql_fetch_assoc($query))
 { $output = $list; 
 }
  mysql_close(); 


 echo json_encode($output);


?>

edit the final "echou" to echo and add

    header('Content-Type: application/json');