Кнопка не работает внутри класса адаптера

    public class WishlistAdapter extends BaseAdapter  {
private ProgressDialog progressDialog;
private LayoutInflater inflater;
private Context mContext;
private List<Response.UserinfoEntity> userinfo;
private static final String SERVER_ADDRESS = "http://www.bruhnancel.xyz/" ;

public interface OnItemClickListener {

public void onItemClicked(int position);

}
private OnItemClickListener listener;

public void setOnItemClickListener(OnItemClickListener listener) {
this.listener = listener;
}
public WishlistAdapter(Context mContext, List<Response.UserinfoEntity> userinfo) {
this.mContext = mContext;
this.userinfo = userinfo;
}

@Override
public int getCount() {
return userinfo.size();
}

@Override
public Object getItem(int position) {
return userinfo.get(position);
}

@Override
public long getItemId(int position) {
return 0;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View rowView = inflater.inflate(R.layout.wishlist_row_item, parent, false);
Response.UserinfoEntity item = (Response.UserinfoEntity) getItem(position);
TextView feedback_name_voted = (TextView)rowView.findViewById(R.id.feedback_name_voted);

// TextView title = (TextView)rowView.findViewById(R.id.title);

TextView comment_posted= (TextView)rowView.findViewById(R.id.comment_posted);
//TextView id = (TextView)rowView.findViewById(R.id.id);
final TextView like_total_number= (TextView)rowView.findViewById(R.id.like_total_number);
ImageView pic = (ImageView)rowView.findViewById(R.id.latest_promotion_pic);

Button delete_wishlist = (Button)rowView.findViewById(R.id.delete_wishlist);
delete_wishlist.setTag(position);
feedback_name_voted.setText("Name = " +item.getAd_title());
comment_posted.setText(item.getCom_name());
like_total_number.setText(item.getAd_id());
Picasso.with(mContext)
.load(item.getImg_link())
.into(pic);delete_wishlist.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
new DeleteWishlist(like_total_number.getText().toString()).execute();
// for the better performance remove auto-boxing
listener.onItemClicked((Integer)v.getTag());
}
});
return rowView;
}private class DeleteWishlist extends AsyncTask<Void, Void, Void> {String  delete;public DeleteWishlist( String delete )
{

this.delete = delete;
}

@Override
protected void onPreExecute() {
super.onPreExecute();
//showProgressDialog("Please wait...", "Your message");

}

@Override
protected Void doInBackground(Void... params) {ArrayList<NameValuePair> dataToSend = new ArrayList<>();dataToSend.add(new BasicNameValuePair("ad_id", delete));try{
HttpParams httpRequestParams = getHttpRequestParams();
HttpClient client = new DefaultHttpClient(httpRequestParams);
HttpPost post = new HttpPost(SERVER_ADDRESS + "delete_wishlst.php");post.setEntity(new UrlEncodedFormEntity(dataToSend));
client.execute(post);

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

return null;
}

@Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);

if(progressDialog != null && progressDialog.isShowing())
{

//progressDialog.dismiss();
Toast.makeText(mContext, "Ads successfully deleted", Toast.LENGTH_SHORT).show();

Intent intent = new Intent(mContext, MainActivity.class);

mContext.startActivity(intent);
}
}
}

private HttpParams getHttpRequestParams(){

HttpParams httpRequestParams = new BasicHttpParams();
HttpConnectionParams.setConnectionTimeout(httpRequestParams, 1000 * 30);
HttpConnectionParams.setSoTimeout(httpRequestParams, 1000*30);
return httpRequestParams;
}

private void showProgressDialog(String title, String message)
{
progressDialog = new ProgressDialog(mContext);

progressDialog.setTitle("Please wait"); //title

progressDialog.setMessage("Uploading"); // message

progressDialog.setCancelable(false);

progressDialog.show();
}
}

а это мой php код

<?php
$con=mysqli_connect("localhost","xx","xx","xx");$ad_id = $_POST["ad_id"];$statement = mysqli_prepare($con, "DELETE  FROM wish_list WHERE ad_id= ?");

mysqli_stmt_bind_param($statement, "s", $ad_id);

mysqli_stmt_execute($statement);

mysqli_stmt_close($statement);

mysqli_close($con);
?>

ошибка

01-22 16:23:46.435 18618-18618/com.example.user.mfpv2 E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.user.mfpv2, PID: 18618
java.lang.NullPointerException
at com.example.user.mfpv2.WishlistAdapter$1.onClick(WishlistAdapter.java:105)
at android.view.View.performClick(View.java:4438)
at android.view.View$PerformClick.run(View.java:18439)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5034)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:611)
at dalvik.system.NativeStart.main(Native Method)

Итак, что я делаю теперь, я пытаюсь отправить запрос в мою базу данных, отправив строку с помощью файла php.

Но это не похоже на работу. Это первый раз, когда я реализую это внутри класса адаптера.