如何在Android中的AsyncTask中执行AsyncTask

Question

I want to start an AsyncTask inside another AsyncTask. I'm trying to do this by starting the second AsyncTask in 'onPostExecute' of the first AsyncTask. The result is that the second AsyncTask starts after the first has finished. How can I solve this?

Thank you

here's the code

private class Parse extends AsyncTask<Void, Void, Void>{
    Document doc = null;
    Element son = null;

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }

    @Override
    protected Void doInBackground(Void... params) {
        try {
            doc = Jsoup.connect("MY_URL").get();
            son= doc.body();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    @Override
    protected void onPostExecute(Void result) {
        super.onPostExecute(result);

        for(CONDITION){
            //MY_CODE

            new DownloadImageTask().execute();

        }
    }
}

This is the second AsyncTask

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

    Bitmap bitmap;
    ImageView image = new ImageView(Events.this);

    @Override
    protected void onPreExecute() {
    };

    protected String doInBackground(String... urls) {
    try {
        URL url = new URL("MY_URL");
        bitmap = BitmapFactory.decodeStream(url.openConnection().getInputStream());
    } catch (MalformedURLException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
        return null;
}

Answer 1

First, please refer to the oficial documentation to have a best understanding about AsyncTask: http://developer.android.com/reference/android/os/AsyncTask.html

The onPostExecute runs in the main thread, after the background task finishes. This method is designed this way to be used to comunicate with the UI thread to handle the execution.

If you want to run the second AsyncTask with your background code, or just after it started, you have to do this on the doInBackground method.