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Slam
Asked:2020-02-19 02:18:11 +0000 UTC2020-02-19 02:18:11 +0000 UTC

paintComponent 不绘制并且应用程序冻结

  • 772

我正在制作一个 Progressbar，paintComponent 应该填充一点。写了以下方法：

GetLastVersionButton.addActionListener(new ActionListener() {
   public void actionPerformed(ActionEvent event) {
       Preferences user = Preferences.userRoot().node("Node");
       Updater updater = new Updater(user.get("FolderDirectory", null) + File.separator + "client.zip");
       updater.downloadClient();
   }
});

这是下载文件：

public void downloadClient() {
        try {
            url = new URL(Utils.getClientUrl());
            url.openConnection();
            inputStream = url.openStream();

            Preferences user = Preferences.userRoot().node("Node");
            folder = new File(user.get("FolderDirectory", null));
            if(!folder.exists()) folder.mkdirs();

            fileOutputStream = new FileOutputStream(outputFile);

            byte[] buf = new byte[1024];

            urlconnection = new URL(url.toString()).openConnection();
            urlconnection.setDefaultUseCaches(false);
            allB += urlconnection.getContentLength();

            logMsg("Скачивание клиента...");

            while ((b = inputStream.read(buf)) > 0) {
                fileOutputStream.write(buf, 0, b);
                buf = new byte[1024];
                downloadB += b;
                System.out.println(downloadB);
                Main.downloadProgressbar.setValue(downloadB, allB);
            }

            fileOutputStream.close();
            inputStream.close();

        } catch (Exception e){}
    }

我故意这样做System.out.println(downloadB);是为了看到paintComponent 的参数总是更新，是的，数字正在运行，一切都应该如此。

如果你while直接删除并发送Main.downloadProgressbar.setValue(downloadB, allB);，那么进度条会分别更新1次，用while，一切都掉下来了。

然后我接受这些值，这里也接受并更新了所有数字：

public void setValue(int bytesDownload, int bytesTotal) {
        allB = bytesTotal;
        downloadB = bytesDownload;
        repaint();
    }

这是paintComponent本身：

protected void paintComponent(Graphics graphics) {
        try {
            Graphics2D g = (Graphics2D) graphics.create();
            Font font = new Font("Arial",Font.TRUETYPE_FONT ,16);
            String done = "Done!";

            double wProgressBarOnline = 434.0 / allB * downloadB;
            double allMB = new BigDecimal(allB * 0.000001).setScale(2, RoundingMode.UP).doubleValue();
            double downloadMB = new BigDecimal(downloadB * 0.000001).setScale(2, RoundingMode.UP).doubleValue();
            double centerXDone = (441.0 / 2) - g.getFontMetrics(font).stringWidth(done) / 2;
            double centerXProgress = (441.0 / 2) - g.getFontMetrics(font).stringWidth((float)downloadMB + "/" + (float)allMB + " MB") / 2;

            String progress = (float)downloadMB + "/" + (float)allMB + " MB";

            g.setFont(font);
            g.setColor(Color.black);

            progressBarBackground = progressBarOnline = check = ImageIO.read(ADownloadProgressbar.class.getResource("/My/Images/progressbar.png"));

            progressBarBackground = progressBarBackground.getSubimage(41, 29, 441,36);
            progressBarOnline = progressBarOnline.getSubimage(45, 0, (int)wProgressBarOnline + 1, 29);
            check = check.getSubimage(0, 29, 41, 36);

            g.drawImage(progressBarBackground, 0, 0, progressBarBackground.getWidth(), progressBarBackground.getHeight(), null);

            g.drawImage(progressBarOnline, 2, 3, progressBarOnline.getWidth(), progressBarOnline.getHeight(), null);
            g.drawString(progress, (int)centerXProgress, 25);


            g.dispose();
            super.paintComponent(graphics);
        } catch(Exception e){e.printStackTrace();}
    }

结果，这样的图片，当你点击按钮时，文件实际上是下载的，所有的东西都下载到了电脑上，但是进度条是死的+应用程序本身冻结了。按钮不起作用，窗口无法移动等，虽然我再说一遍，下载没有中断，调试过程中没有错误。

如果您能提供帮助，我将不胜感激！

java

1 个回答

  1. Best Answer

    事实是您在一个线程中完成所有这些，并且在完成整个过程之前，您的面板不会重绘。像这样试试

    public void downloadClient() {
        new Thread(new Runnable(){

            @Override
            public void run() {

                try {
                    url = new URL(Utils.getClientUrl());
                    url.openConnection();
                    inputStream = url.openStream();

                    Preferences user = Preferences.userRoot().node("Node");
                    folder = new File(user.get("FolderDirectory", null));
                    if (!folder.exists()) folder.mkdirs();

                    fileOutputStream = new FileOutputStream(outputFile);

                    byte[] buf = new byte[1024];

                    urlconnection = new URL(url.toString()).openConnection();
                    urlconnection.setDefaultUseCaches(false);
                    allB += urlconnection.getContentLength();

                    logMsg("Скачивание клиента...");

                    while ((b = inputStream.read(buf)) > 0) {
                        fileOutputStream.write(buf, 0, b);
                        buf = new byte[1024];
                        downloadB += b;
                        System.out.println(downloadB);

                        SwingUtilities.invokeLater(new Runnable() {
                            @Override
                            public void run() {
                                Main.downloadProgressbar.setValue(downloadB, allB);
                            }
                        });
                    }

                    fileOutputStream.close();
                    inputStream.close();

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

    您可以以不同的方式处理它并在SwingWorker中启动下载过程- 这是一个更正确的选择。

    • 2

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