Question

So I have a little app I am working on that scrapes comics from the web and displays them on my phone. Nothing fancy, just using it to learn the ropes. The function called comicReload(); does most of the work and it is called many times in the application (on first run, and when the user clicks certain buttons. Here is the function:

public void comicReload () throws IOException {
    //clears some Vectors that have things in them from the last run
    imagetitles.clear();
    imagetext.clear();
    imagelinks.clear();

    //forms the link it will connect to, and connects
    connector = siteBase + Integer.toString(comicNumber);
    doc = Jsoup.connect(connector).get();
    media = doc.select("[src]");

    //gets the required media from the site
    for (Element src : media) {
        if (src.tagName().equals("img"));
            imagetitles.add(src.attr("alt"));
            imagetext.add(src.attr("title"));
            imagelinks.add(src.attr("src"));
    }

    //some variables I could probably get rid of, but it's easy to read
    Integer titlesize = imagetitles.size();
    Integer textsize = imagetext.size();
    Integer linkssize = imagelinks.size();

    comicTitle = (imagetitles.get(titlesize-4));
    hoverText = (imagetext.get(textsize-4));
    comicLink = (imagelinks.get(linkssize-4));

    //gets the picture I am looking for along with the associated text
    URL url = new URL(comicLink);
    InputStream is = (InputStream) url.getContent();
    image = Drawable.createFromStream(is, "src name");

    //finally puts the scraped information into the layout
    comicView.setImageDrawable(image);
    title.setText(comicTitle);
    htext.setText(hoverText);
}

It works 100% fine when it is called, but it’s a little slow over 3G so I tried to add a ProgressDialog to show while it loads. This is my attempt (this is the code that runs where I used to just have comicReload();)

pd = ProgressDialog.show(this, "Getting Comic", "Loading", true, false);
    new Thread(new Runnable() {  
           public void run() {
               try {
                   comicReload();
               } catch (IOException e) {
                   Log.i("ComicReloadFail","Sam");
               }
               pd.dismiss();
               return;
           }
    }).start();

The Thread itself runs fine, and when I put some random code to execute in place of the try-catch block with the comicReload(); in it everything goes dandy. The second I put the comicReload() back in there, however, running the app causes the ProgressDialog spinner to spin for a few seconds before the app force closes. What is causing this? And why does comicReload() stop working when it’s in a thread. I just want a way to execute that method with a spinner going while it works.

Thanks in advance guys, I know that was a lot to read.

Answer 1

you can not do UI related updates in a different thread than the one that created the UI.

try using Handler

public static final Handler handlerVisibility = new Handler() {
    public void handleMessage(Message msg) {
        int visibility = msg.getData().getInt("visibility");
        view.setVisibility(visibility);
    }
};