setContentView unavailable from AsyncTask

Issue

I am writiing a java application on Android. I have an Activity which starts an AsyncTask in order to get data from server and the to present it.

I am trying to present the data in onPostExecute() method but some how setContentView & populateUI(getApplicationContext()) not resolved in its scope. Why?

If run a code like this, without adding setContentView I get an empty screen at the end of execution. No exception appears.

public class CurrencyRatesActivity extends Activity
{
   @Override
   protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    new ReadCurrencyRateTask(this).execute("http://currency.xml");
   }
}


public class ReadCurrencyRateTask extends AsyncTask<String, Integer, Integer>
{
   private Context mainActivityContext;

   public ReadCurrencyRateTask(Context mainActivityContext)
   {
       super();
       this.mainActivityContext = mainActivityContext;
   }

   public Integer doInBackground(String... url)
   {
       // do some culculations
       .......
       return status;
   }

   protected void onPostExecute(Integer result)
   {

       // In case connection succeeded
       TableLayout tbl = new TableLayout(mainActivityContext);
       tbl.setStretchAllColumns(true);
       tbl.bringToFront();

       for (int i=0; i<currencyList.size(); i++)
       {
           TableRow tr =  new TableRow(mainActivityContext);
           TextView country = new TextView(mainActivityContext);
           country.setText("...something...");
           tr.addView(country);
       }
   }
}

Thanks

Solution

Actually you only answered your question "not resolved in its scope" and really it is.
try this

public class CurrencyRatesActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        new ReadCurrencyRateTask(this).execute("http://currency.xml");
    }

    class ReadCurrencyRateTask extends AsyncTask<String, Integer, Integer> {

        //your network stuff goes here

        @Override
        protected void onPostExecute(Integer integer) {
            super.onPostExecute(integer);
            //your stuff
            setContentView(yourView);
        }

    }

}

1. Declare the AsyncTask inside activity so that you access all the activity methods.
2. Or If you have AsyncTask in separate class then use interface as callbacks and do Update UI stuff in activity.

Important : You can update UI only from UI thread and from Activity.

Answered By - Bharatesh