Question

I have the following code:

public class TestSynch extends Activity {

public static ArrayList<HashMap<String,String>> list;

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.splash);
    Context ctx = this.getApplicationContext();


    new ProcessFileTask().execute(ctx);

    Intent i = new Intent(TestSynch.this, ListSchools.class);
    i.setAction(Intent.ACTION_VIEW);
    i.putExtra("arraylist", list);
    startActivity(i);

}

private class ProcessFileTask extends AsyncTask<Context, Void, ArrayList<HashMap<String,String>>> {
    @Override
    protected ArrayList<HashMap<String,String>> doInBackground(Context... ctx) {

        ArrayList<HashMap<String,String>> threadList = FileOperations.getListAsMaps(ctx[0]);
        return threadList;
    }
    @Override
    protected void onPostExecute(ArrayList<HashMap<String,String>> result) {
         list = result;
        return;
    }
}

I can debug to the return threadList; line in doInBackground, and the ArrayList variable threadList is perfectly correct.

However, onPostExecute doesn’t seem to get called and the Activity crashes on return from doInBackground, with LogCat suggesting a nullPointerException attempting to fire the Intent (which I have previously tested and worked ok before I started messing with AsynchTask)

Any idea why this is happening? The code seems simple enough…

Thanks

Answer 1

I think Waqas is correct. You are performing an AsyncTask that after it has executed sets a public static variable list. This list is used to pass into the Intent that you create in onCreate. However there is no guarantee that the AsyncTask has actually completed at the point when you create the Intent. As such the value of list at this point is null.

So, as Waqas suggests, you need to create the Intent after you have set a value for list, i.e. within onPostExecute.