Question

I’ve used AsyncTask quite a bit – but I have come across a seemingly simple question that confused me. The question is this:

Is publishProgress(Progress... values) supposed to return
immediately? In other words, is this method asynchronous?

Some Context:

I’m trying to determine whether the following code

• Fires an HTTP request every three seconds, regardless of the response OR
• Fires an HTTP request, waits for the response, and then sleeps for three seconds before firing the next request.

public class MyAsyncTask {

@Override
protected void doInBackground(String... params) {
    while (mRunning) {
        // Call publishProgress
        this.publishProgress(makeHttpRequest());

        // Sleep for 3 seconds
        synchronized (lock) {
            try {
                lock.wait(3 * 1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    return null;
}

private HttpResponse makeHttpRequest() {
    HttpResponse ajaxResponse = null;
    Throwable throwable = null;
    try {
        ajaxResponse = mHttpClient.execute(mHttpGet);
    } catch (ClientProtocolException e) {
        // Handle exception
    } catch (IOException e) {
        // Handle exception
    } catch (Exception e) {
        // Handle exception
    }

    return ajaxResponse;

}

@Override
protected void onProgressUpdate(HttpResponse... values) {
    // Do something with the response
}

}

Answer 1

this.publishProgress(makeHttpRequest());

is equals to (Java can’t pass methods. Just the results)

HttpResponse resp = makeHttpRequest();
this.publishProgess(resp);

so makeHttpReqest is done in the background.

You than pass the HttpResponse Object to publishProgress which returns immediately. The progress Object is then asynchronously send to onProgressUpdate() in the UI thread.

-> it’s the then sleeps way.