java – JProgressBar不会更新

public void downloadImages(List<String> images) {
    if (errorCode == 0) {
        for (int i = 0; i < images.size(); i++) {
            if (errorCode == 0) {
                main.progressLabel.setText("Downloading image " + Integer.toString(i + 1) + " of " + Integer.toString(images.size()));
                String imageStr = images.get(i);
                String imageName = imageStr.substring(imageStr.lastIndexOf("/") + 1);
                try {
                    URL url = new URL(imageStr);
                    InputStream in = url.openStream();
                    OutputStream out = new FileOutputStream(saveDirectory + imageName);

                    byte[] b = new byte[2048];
                    int length;
                    while ((length = in.read(b)) != -1) {
                        out.write(b, 0, length);
                    }

                    in.close();
                    out.close();
                } catch (MalformedURLException e) {
                    errorCode = BAD_URL;
                } catch (IOException e) {
                    errorCode = INVALID_PATH;
                }
                main.progressBar.setValue(((i+1)/images.size())*100);
            }

        }
    }
}

更改进度条值位于上述方法的底部.

以下是我称之为该方法的方法.

public void download() {
    final Downloader downloader = new Downloader(this, albumUrl.getText(), downloadPath.getText());
    progressBar.setValue(0);
    downloadButton.setEnabled(false);

    new Thread(new Runnable() {
        public void run() {
            List<String> images = downloader.getImages(downloader.getPageSource());
            downloader.downloadImages(images);
            if (downloader.getErrorCode() == 0) {
                progressLabel.setText("All images have been downloaded!");
            } else {
                String error = "";
                switch (downloader.getErrorCode()) {
                case Downloader.BAD_URL:
                case Downloader.NOT_IMGUR_ALBUM:
                    error = "The URL entered is either invalid or does not link to an Imgur album.";
                    break;
                case Downloader.BLANK_URL:
                    error = "The album URL field cannot be blank.";
                    break;
                case Downloader.INVALID_PATH:
                    error = "The system cannot find the download directory path specified.";
                    break;
                case Downloader.BLANK_PATH:
                    error = "The download directory cannot be blank.";
                    break;
                case Downloader.CANNOT_READ_URL:
                    error = "An error occoured while reading the URL.";
                    break;
                case Downloader.PARSING_ERROR:
                    error = "An error occoured while parsing the URL.";
                    break;
                }
                JOptionPane.showMessageDialog(Main.this, error, "Error", 0);
            }
            downloadButton.setEnabled(true);
        }
    }).start();
}

编辑：上面的问题根本不是问题,程序使用整数除法而不是小数.

main.progressBar.setValue((int)((i 1)/(double)images.size())/ 100))

这样做是为了确保i 1被一个支持十进制的数据类型划分,它将返回更具包容性的数据类型(在这种情况下为double),然后它将一个double除以int这将没有问题,因为它仍然会返回一个双倍,因为它更具包容性.然后我们将它转​​换为int,因为这是setValue()想要的数据类型.