problem description

as mentioned, it is invalid to modify Title in the onPostExecute of AsyncTask without any errors

related codes

onCreate:

toolbar=(Toolbar) findViewById(R.id.main_toolbar);
setSupportActionBar(toolbar);
Simple simple=new Simple();
simple.execute("");

AsyncTask:

private class Simple extends AsyncTask<String,String,String>
    {

        @Override
        protected void onPreExecute()
        {
            setTitle("...");
            super.onPreExecute();
        }


        @Override
        protected String doInBackground(String[] p1)
        {
            try
            {
                Thread.sleep(1000);
                
            }
            catch (InterruptedException e)
            {}
            return "";
        }

        @Override
        protected void onPostExecute(String result)
        {
            super.onPostExecute(result);
            setTitle(result);
            
        }

the environmental background of the problems and what methods you have tried

setTitle in onPostExecute has tried toolbar.setTitle and MainActivity.this.setTitle