data not retrieving from online mysql server

Question

I am trying to get data from online database(MySql) through json and want to display it as a ListView. What I've done so far :

Downloader.java

public class Downloader extends AsyncTask<Void,Integer,String> { Context c; String address; ListView lv; ProgressDialog pd; public Downloader(Context c, String address, ListView lv) { this.c = c; this.address = address; this.lv = lv; } //B4 JOB STARTS @Override protected void onPreExecute() { super.onPreExecute(); pd=new ProgressDialog(c); pd.setTitle("Fetch Data"); pd.setMessage("Fetching Data...Please wait"); pd.show(); } @Override protected String doInBackground(Void... params) { String data=downloadData(); return data; } @Override protected void onPostExecute(String s) { super.onPostExecute(s); pd.dismiss();; if(s != null) { Parser p=new Parser(c,s,lv); p.execute(); }else { Toast.makeText(c,"Unable to download data",Toast.LENGTH_SHORT).show(); } } private String downloadData() { //connect and get a stream InputStream is=null; String line =null; try { URL url=new URL(address); HttpURLConnection con= (HttpURLConnection) url.openConnection(); is=new BufferedInputStream(con.getInputStream()); BufferedReader br=new BufferedReader(new InputStreamReader(is)); StringBuffer sb=new StringBuffer(); if(br != null) { while ((line=br.readLine()) != null) { sb.append(line+"n"); } }else { return null; } return sb.toString(); } catch (MalformedURLException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); }finally { if(is != null) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } } return null; }

}

MainActivity.java

public class MainActivity extends Activity { String url="http://bookvilla.esy.es/book.php"; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); final ListView lv= (ListView) findViewById(R.id.lv); final Downloader d=new Downloader(this,url,lv); d.execute(); } }

when i run the app the app.. i get a toast message saying "unable to download data" which is in the 35th line of Downloader.java class. So i am guessing that the data i am getting from the database is null ...but why is it so ....

$con = mysqli_connect($host,$u_name,$pwd,$db) or die('Unable to connect'); if(mysqli_connect_error($con)) { echo "Failed to connect to database".mysqli_connect_error();

}

$query = mysqli_query($con,"SELECT * FROM playerstb"); if($query) {

while($row=mysqli_fetch_array($query)) { $flag[] = $row;

} print(json_encode($flag)); } mysqli_close($con);

above is my php file

is private String downloadData() even called? i don't think so. i think you forgot to override the public void execute() Method — Japu_D_Cret
– Japu_D_Cret, Commented Mar 25, 2017 at 18:33

Dennis Str · Accepted Answer · 2017-03-27 13:38:36Z

Not sure how to fix your issue but I used a different method:

db_config.php:

<?php define('DB_USER',"root"); define('DB_PASSWORD',null); define('DB_DATABASE',"phoneshop"); define('DB_SERVER',"localhost"); ?>

db_connect.php:

<?php class DB_CONNECT { private $con = ''; function __construct() { $this->connect(); } function __destruct() { $this->close(); } function connect() { require_once __DIR__ . '/db_config.php'; $this->con = mysqli_connect(DB_SERVER , DB_USER , null , DB_DATABASE) or die(mysqli_error()); return $this->con; } function close() { mysqli_close($this->con); } function query($query){ return mysqli_query($this->con, $query); } } ?>

And then I made this file to receive data:

<?php $response = array(); require_once __DIR__ . '/db_connect.php'; $db = new DB_CONNECT(); $result = $db->query('SELECT * FROM products') or die('error'); if (mysqli_num_rows($result) > 0) { $response["products"] = array(); while ($row = mysqli_fetch_array($result)) { $product = array(); $product["pid"] = $row["pid"]; $product["name"] = $row["name"]; $product["price"] = $row["price"]; $product["description"] = $row["description"]; array_push($response["products"], $product); } $response["success"] = 1; echo json_encode($response); } else { $response["success"] = 0; $response["message"] = "No products found"; echo json_encode($response); } ?>

And then from Android studio:

The call:

private String url_all_products = "http://10.0.0.10:8012/onlineShop/get_all_products.php"; //ip of the server or 10.0.2.2 if in emulator ContentValues params = new ContentValues(); JSONObject json = jParser.makeHttpRequest(url_all_products, "GET", params);

And the Parser:

public class JSONParser { static JSONObject jObj; static String json; // constructor public JSONParser() { } // function get json from url // by making HTTP POST or GET mehtod public static JSONObject makeHttpRequest(String url, String method, ContentValues params) { // Making HTTP request try { final OkHttpClient client = new OkHttpClient(); Request request; // check for request method if (method.equals("POST")) { // request method is POST MediaType contentType = MediaType.parse("application/x-www-form-urlencoded; charset=UTF-8"); String content = ""; for (String key : params.keySet()) { if ( !content.isEmpty()) content += "&"; content += key + "=" + params.get(key); } RequestBody body = RequestBody.create(contentType, content); request = new Request.Builder().url(url).post(body).build(); } else { // request method is GET request = new Request.Builder().url(url).build(); } final Response response = client.newCall(request).execute(); json = response.body().string(); } catch (IOException e) { e.printStackTrace(); } // try parse the string to a JSON object try { jObj = new JSONObject(json); } catch (JSONException e ){ Log.e("JSON Parser", "Error parsing data " + e.toString()); } // return JSON String return jObj; } }

While adding this to the gradle:

compile 'com.squareup.okhttp3:okhttp:3.4.2'

Bro i solved my error ...that was a silly mistake ....i put the "http://" two times..lol.anyways thankyou for giving your time.
in the second line of MainActivity.java ...you won't see it because I've edited the question.

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