我想知道为什么不向MySQL发送数据？

I want to send data to the database.My PHP Files are OK,because I had tested that with postman and it send data to the database.But when I used Android app for that it shouldn't send data to the database.Here is my java method for the sending data.Reply me with the solution please.

 public void insertData(String name,String category,int quantity){
        String url = "http://192.168.172.2/foods/insert.php";
    try {
        String data = URLEncoder.encode("name", "UTF-8")
                + "=" + URLEncoder.encode(name, "UTF-8");

        data += "&" + URLEncoder.encode("category", "UTF-8") + "="
                + URLEncoder.encode(category, "UTF-8");

        data += "&" + URLEncoder.encode("quantity", "UTF-8")
                + "=" + URLEncoder.encode(String.valueOf(quantity), "UTF-8");


        URL url1 = new URL(url);
        HttpURLConnection connection = (HttpURLConnection) url1.openConnection();
        connection.setRequestMethod("POST");
        connection.setDoOutput(true);
        OutputStreamWriter writer = new OutputStreamWriter(connection.getOutputStream());
        writer.write(data);
        writer.flush();

        Log.d("datainsert","success"+data);

    } catch (MalformedURLException e) {
        Log.d("datainsert","Error"+e.getMessage());

    } catch (IOException e) {
        Log.d("datainsert","Error"+e.getMessage());
   }

<?PHP
require "config.php";

global $connect;

if (isset($_POST['name']) and isset($_POST['category']) and isset($_POST['quantity'])) {
$name = $_POST['name'];
$category = $_POST['category'];
$quantity = $_POST['quantity'];
$intq = (int)$quantity;


if ($_SERVER['REQUEST_METHOD']== "POST") {

$query = "INSERT INTO food_details(food_name,category,quantity) VALUES('$name','$category',$intq);";

  if($q = mysqli_query($connect,$query)){
    echo "successfully inserted";
  }else{
  //echo  mysqli_error(mysqli_query($connect,$query));
    echo "not success";
    echo "Error: " . $query . "<br>" . $connect->error;
  }
}
}

mysqli_close($connect);
?>

Sending Data to server using POST method Uri.Builder class for creating query String.As follows

Uri.Builder builder = new Uri.Builder()
        .appendQueryParameter("firstParam", paramValue1)
        .appendQueryParameter("secondParam", paramValue2)
String query = builder.build().getEncodedQuery();

For your question specific your post method will be as follows

try {
        URL url = new URL("http://192.168.172.2/foods/insert.php");
        HttpsURLConnection conn = (HttpsURLConnection) url.openConnection();
        conn.setReadTimeout(10000);     //change according to need 
        conn.setConnectTimeout(15000);  //change according to need 
        conn.setRequestMethod("POST");
        conn.setDoInput(true);
        conn.setDoOutput(true);

        Uri.Builder builder = new Uri.Builder()
                .appendQueryParameter("name", name)
                .appendQueryParameter("category", category)
                .appendQueryParameter("quantity", quantity);
        String query = builder.build().getEncodedQuery();

        OutputStream os = conn.getOutputStream();
        BufferedWriter writer = new BufferedWriter(
                new OutputStreamWriter(os, "UTF-8"));
        writer.write(query);
        writer.flush();
        writer.close();
        os.close();

        conn.connect();

        //get response from server
        String response = conn.getResponseMessage();
        Log.d("URl->", response);

    } catch (IOException e) {
        e.printStackTrace();
    }

I hope its work for you