You can pass to the AsynkTast the instance of the TextView as a parameter, and call setText in onPostExecute.

in your case, simply following will come here:

((TextView)findViewById(R.id.xyz)).setText("abc");

I picked the solution from

How do I return a boolean from AsyncTask?

new Task(getActivity()).execute(query);

In the Constructor of AsyncTask

TheInterface listener;
public Task(Context context)
{
  listener = (TheInterface) context; 
}

Interface

public interface TheInterface {

public void theMethod(String result); // your result type

 }

Then

In your doInbackground return the result.

In your onPostExecute

if (listener != null) 
{
  listener.theMethod(result); // result is the String
  // result returned in doInbackground 
  // result of doInbackground computation is a parameter to onPostExecute 
}

In your activity class or fragment implement the interface

public class ActivityName implements Task.TheInterface

Then

@Override
 public void theMethodString result) { 
    tv.setText(result); 
    // set the text to textview here with the result of background computation
    // remember to declare textview as a class member.
 }

Edit:

You are also missing @Override annotation for your onPostExecute