class Tasks {
 
    static TaskExport taskExport;
 
    static class TaskExport extends AsyncTask<String, String, Boolean> {
 
            @Override
            protected void onPreExecute() {
                super.onPreExecute();
    
                progressDialog = new ProgressDialog(mainActivity);
                progressDialog.setIndeterminate(true);
                progressDialog.setCancelable(false);
    
                progressDialog.setButton(BUTTON_NEGATIVE, mainActivity.getString(R.string.Cancel),
                        new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialogInterface, int i) {
                                if (taskExport != null) {
                                    taskExport.cancel(true);
                                }
                                progressDialog.dismiss();
                            }
                        });
    
                progressDialog.show();
            }
        }
    
    
        @Override
        protected Boolean doInBackground(String... urls) {
            //....................................
            //....................................
            return true;
        }
    
    
        @Override
        protected void onPostExecute(Boolean result) {
            //....................................
            //....................................
        }
    
    
        @Override
        protected void onCancelled() {
            super.onCancelled();
            //....................................
            //....................................
        }
    
    
        @Override
        protected void onProgressUpdate(String... value) {
            super.onProgressUpdate(value);
            //....................................
            //....................................
        }
    }
}