AsyncTask控件UI线程

Question

Code i have use

public class DemoAsynTask extends AsyncTask{
@Override
 protected void onPreExecute(){      
     try{           

         MainActivity myActivity = new MainActivity();
         myActivity.super.onCreate(savedInstanceState);
         myActivity.setContentView(R.layout.activity_main);

         EditText txtInformation = (EditText) myActivity.findViewById(R.id.txtInformation);
     txtInformation.setText("TESTING");
     }catch(Exception ex){
        ex.printStackTrace(); 
     }
}
    @Override
    protected Object doInBackground(Object... params) {
        // TODO Auto-generated method stub
        return null;
    }
}

The DemoAsynTask class is not inside, i have seen an example is work but class inside MainActivity

public class MainActivity extends activity{
   public class DemoAsynTask extends AsyncTask{
   }
}

The DemoAsynTask class is seperate files and i want call it seperately but it have null pointer exception.

public class MainActivity extends activity{
}
public class DemoAsynTask extends AsyncTask{
}

Error Log java.lang.NullPointerException

Answer 1

Hey you create the MainActivity (no need instantiating of MainActivity let it be instantiated as per activity life cycle) and take DemoAsyncTask as another class or as internal class of MainActivity. In onPreExecute() you set the status "TESTING" and in the onPostExecute() change the status as per the result you get in doInBackground().