gistfile1.java

public class MyAsyncTask extends AsyncTask {
    WeakReference<MyActivityInterface> mCaller;
    
    public MyAsyncTask(MyActivityInterface caller) {
        mCaller = caller;
    }
    
    // here comes code
    
    public void onPostExecute(Object result) {
        if(mCaller.get() != null) {
            mCaller.doSomething();
        }
    }
}