如何从内部AsyncTask类的onPostExecute方法修改外部字段？

Question

In the following snippet:

public class ExternalClass {
    private int num = 1;

    public void backgroundTask() {
        new HttpTask().execute();
    }

    public int getNum() {
        return num;
    }

    private class HttpTask extends AsyncTask<String, Void, String> {

        @Override
        protected String doInBackground(String... params) {
            //Do stuff...
        }

        @Override
        protected void onPostExecute(String result) {
            //Do stuff...
            ExternalClass.this.num = 2;
    }
}

In an Activity:

...
ExternalClass ec = new ExternalClass();
ec.backgroundTask();
int myNum = ec.getNum(); //NUM IS 1, NOT 2!!

What am I doing wrong? Everything works fine, my doInBackground() and onPostExecute() complete successfully but the field "num" don't change. I tried "num = 2" or even "this.num = 2" (I know is no correct, but...).

Answer 1

you will need to use AsyncTask.get() method to get result back in Main UI Thread from AsyncTask when doInBackground() execution complete

public void backgroundTask() {
        new HttpTask().execute().get();
    }

NOTE: when u call get() method of AsyncTask in Main UI thread this will stop exection of Main Thread . you will need to call backgroundTask() method from background Thread