CODEWITHSUNDEEP
javaandroidandroid-asynctask
Jake
Jake

Reputation: 109

Cannot update UI from AsyncTask

I know that this is most likely going to be marked a duplicate, but this is extremely frustrating me. I cannot, for the life of me, figure out a way to modify a textview from an AsyncTask. This is my function that is in the MainActivity class:

public void updateTextView(String data){
    TextView textview = (TextView)findViewById(R.id.TextView1);
    textview.setText(data);
}

and then in my AsyncTask i have

@Override
protected void onPostExecute(String result) {
    MainActivity ma = new MainActivity();
    ma.updateTextView(result);
}

However, after running this code and any modifications that involve attempting to modify the TextView from the AsyncTask, I get:

java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.Window$Callback android.view.Window.getCallback()' on a null object reference

However when calling the same exact function from the main thread, it runs fine.

Any help would be greatly appreciated.

Upvotes: 0

Views: 1317

Answers (1)

Ali Gholami
Ali Gholami

Reputation: 36

you connot make a new object from an activity and work with it. try to get a reference to the activity

add this code to your AsyncTask class

MainActivity activity;

public void setContext(MainActivity activity){
    this.activity = activity;
  }

also edit this

@Override
protected void onPostExecute(String result) {
     activity.updateTextView(result);
   }

call this method when you create your AsyncTask object in your activity

//at is the object you created from your AsyncTask Class
at.setContext(this);

Upvotes: 2

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