下载时JFrame进度条不会更新

Question

我为我的游戏制作了一个小型启动器，我试图让它下载一些文件。一切都有效，除了进度条和它上面的JLabel。他们下载时不会更新。以下是我的一些代码：

static void checkForUpdates() {
    Gui.progressBar.setIndeterminate(true);
    Gui.status.setText("Status: Checking for cache updates...");
    try {

        double newest = getNewestVersion();
        double current = getCurrentVersion();
        if(newest > current) {
            downloadCache();
            unzipCache();
            setLatestCacheVersion(newest);
        }

    } catch(Exception e) {
        e.printStackTrace();
    }
}

private static void downloadCache() throws IOException {
    Gui.progressBar.setIndeterminate(false);
    URL url = new URL(Configuration.CACHE_URL);
    HttpURLConnection httpConn = (HttpURLConnection) url.openConnection();
    httpConn.addRequestProperty("User-Agent", "Mozilla/4.76");
    int responseCode = httpConn.getResponseCode();

    if (responseCode == HttpURLConnection.HTTP_OK) {
        String fileName = Configuration.CACHE_NAME;
        InputStream inputStream = httpConn.getInputStream();
        String saveFilePath = Configuration.SAVE_DIRECTORY + fileName;

        FileOutputStream outputStream = new FileOutputStream(saveFilePath);

        int bytesRead = -1;
        byte[] buffer = new byte[4096];
        long numWritten = 0;
        int length = httpConn.getContentLength();
        while ((bytesRead = inputStream.read(buffer)) != -1) {
            outputStream.write(buffer, 0, bytesRead);
            numWritten += bytesRead;
            int percentage = (int)(((double)numWritten / (double)length) * 100D);
            Gui.progressBar.setValue(percentage);
            Gui.progressBar.repaint();
        }

        outputStream.close();
        inputStream.close();

    } else {
        System.out.println("Cache host replied HTTP code: " + responseCode);
    }
    httpConn.disconnect();
}

它一直在说：检查更新，因为这是我在开始时设置的内容，但在此之后它不会更新。

static JLabel status = new JLabel("Checking for updates...", SwingConstants.CENTER);

我做了一些研究，我发现如果我没有弄错的话，我必须和swingworker做点什么。问题是我不知道在这种情况下我会怎么做。