Question

我正在创建一个具有多个更新功能的Swing GUI。如果用户未正确更新，则会显示“下载并安装”按钮。这很好，但按下按钮什么都不做。它不冻结，只是坐在那里。尽管如此，“setup.exe”是一个相当大的文件（~600MB），但它没有显示任何内容，也没有文件甚至开始出现在C：\目录中。我在这做错了什么？

protected static JButton aroundTheLake; 

private static JButton aroundTheRiver() {
    aroundTheLake = new JButton("DOWNLOAD & INSTALL!");
    aroundTheLake.setVerticalTextPosition(AbstractButton.CENTER);
    aroundTheLake.setHorizontalTextPosition(AbstractButton.LEADING); //aka LEFT, for left-to-right locales
    aroundTheLake.setMnemonic(KeyEvent.VK_D);
    aroundTheLake.setActionCommand("aroundthelake");
    return aroundTheLake;
}

private static String readURL(String targetURL) {
    String returnish = "";
    try {
        URL tempURL = new URL(targetURL); 
        Scanner s = new Scanner(tempURL.openStream()); 
        while (s.hasNextLine()) {
            returnish = returnish+s.nextLine(); 
        }
    } catch (IOException e) {
        System.out.println(e); 
    }
    return returnish;
}

private static String readFile(String targetFile) { 
    String returnString = "";
    try {
        File tempFile = new File(targetFile);
        Scanner s = new Scanner(tempFile);
        while (s.hasNextLine()) {
            returnString = returnString + s.nextLine(); 
        }
    } catch(IOException e) { 
        // !
        System.out.println(e);
    }
    return returnString;
}

public void actionPerformed(ActionEvent e) {
    if ("aroundthelake".equals(e.getActionCommand())) {
        try { 
                System.out.println("initiated");
                URL website = new URL("http://theneverhood.sourceforge.net/setup.exe");
                ReadableByteChannel rbc = Channels.newChannel(website.openStream());
                FileOutputStream fos = new FileOutputStream("setup.exe");
                fos.getChannel().transferFrom(rbc, 0, 1 << 24);
        } catch (IOException exc) { 
            System.out.println(exc);
        }
    } else {
        // man
    }
}

private static void showGUI() {
    JFrame frame = new JFrame("The Neverhood Restoration Project");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setSize(new Dimension(1024, 600));
    frame.setExtendedState(frame.MAXIMIZED_BOTH);
    frame.getContentPane().setBackground(new Color(0xA64343));

    File fileCheck = new File("C:/Program Files (x86)");
    String returnString = null;
    String rootDirectory = null;
    if (fileCheck.exists()) {
        rootDirectory = "C:/Program Files (x86)/DreamWorks Interactive"; 
        String checkFile = rootDirectory+"/Neverhood/version.txt"; 
        File tempFile = new File(checkFile);
        if (tempFile.exists()) {
            returnString = readFile(checkFile);
        } else {
            returnString = "It appears you do not have the Neverhood Restoration Project installed, or you are using an earlier version."; 
        }
    } else {
        rootDirectory = "C:/Program Files/DreamWorks Interactive";
        String checkFile = rootDirectory+"/Neverhood/version.txt"; 
        File tempFile = new File(checkFile);
        if (tempFile.exists()) {
            returnString = readFile(checkFile);
        } else {
            returnString = "It appears you do not have the Neverhood Restoration Project installed, or you are using an earlier version.";
        }
    }
    if (returnString.equals(readURL("http://theneverhood.sourceforge.net/version.txt"))) {
        returnString = "You are updated to the recent version!"; 
    } else { 
        returnString = "It appears you're not updated.";
    }

    JLabel headerLabel = new JLabel("The Neverhood Restoration Project");
    headerLabel.setHorizontalAlignment(JLabel.CENTER);
    JPanel heapPanel = new JPanel();
    heapPanel.setLayout(new BoxLayout(heapPanel, BoxLayout.PAGE_AXIS));
    heapPanel.setPreferredSize(new Dimension(500, heapPanel.getPreferredSize().height));
    JTextArea heapLabel = new JTextArea(50, 50);        
    heapLabel.setLineWrap(true);
    heapLabel.setWrapStyleWord(true);
    heapLabel.setEditable(false);
    heapLabel.setBorder(BorderFactory.createEmptyBorder(10, 20, 10, 20));
    heapLabel.setFont(new Font("Serif", Font.PLAIN, 14));
    heapLabel.append("Current version: "+readURL("http://theneverhood.sourceforge.net/prettyversion.txt")+".\nInstalled version: "+readFile(rootDirectory+"/Neverhood/prettyversion.txt")+".\n"+returnString+"\n" + 
        "You can read the full version of the document to the left at http://theneverhood.sourceforge.net."
        + "\nHaven't installed yet? Below is the download button. Just click to save setup.exe in and enjoy!");
    heapPanel.add(heapLabel);
    if (returnString == "It appears you're not updated.") { 
        heapPanel.add(aroundTheRiver());
    }

    try {
        Font sFont = Font.createFont(Font.TRUETYPE_FONT, new File("DUGFB___.TTF"));
        sFont = sFont.deriveFont(Font.PLAIN, 48);
        GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
        ge.registerFont(sFont);
        headerLabel.setFont(sFont);
    } catch (FontFormatException | IOException e) {
        System.out.println(e);
    }

    BufferedImage icoImage = null;
    try {
        icoImage = ImageIO.read(
            frame.getClass().getResource("/nhood.bmp"));
    } catch (IOException e) {
        System.out.println(e);
    }
    frame.setIconImage(icoImage);

    JEditorPane updateLog = new JEditorPane();
    JScrollPane scrollPane = new JScrollPane(updateLog);
    updateLog.setEditable(false);

    try {
        updateLog.setPage("http://theneverhood.sourceforge.net/");
    } catch (IOException e) {
        updateLog.setContentType("text/html");
        updateLog.setText("<html>The application could not load the webpage.</html>");
    }

    frame.add(headerLabel, BorderLayout.NORTH);
    frame.add(scrollPane);
    frame.add(heapPanel, BorderLayout.EAST);
    frame.pack();
    frame.setVisible(true);
}


public static void main(String[] args) {
    javax.swing.SwingUtilities.invokeLater(new Runnable() {
        @Override
        public void run() {
            showGUI();
        }
    });
}

Answer 1

您的代码中有两个主要问题：

您尚未将动作侦听器注册到按钮。这样做：

button.addActionListener(this);

actionPerformed()在GUI线程（EDT）上执行，因此请避免对其执行密集操作。而是使用SwingWorker。见How SwingWorker works。

Answer 2

有几件事：

1）从不从Swing线程进行网络调用！使用SwingWorker。当Swing EDT被阻止时，所有UI操作都将停止。有关详细信息，请参阅here。

2）你真的不需要覆盖JButton。只需添加一个ActionListener即可。你这样使你的代码变得不那么灵活。

3）确保您实际拨打addActionListener()。

Answer 3

用户界面冻结，因为您要保持事件调度线程忙于下载。

事件派发线程是维持UI“活着”的相同线程 - 你应该永远做任何在事件处理程序中直接感知很长时间的事情。

您应该做的是启动一个单独的线程来下载文件。为了使用户友好，您可以使用progress monitor，以便用户可以看到您的程序正在执行的操作，理想情况下可以使用多长时间。我建议您浏览一下tutorial，看看是如何完成的。

快速解决方案就是启动一个新线程。这不是非常用户友好，因为绝对没有用户反馈。

public void actionPerformed(ActionEvent e) {
    if ("aroundthelake".equals(e.getActionCommand())) {
        new Thread() {
            public void run() {
                try { 
                    System.out.println("initiated");
                    URL website = new URL("http://theneverhood.sourceforge.net/setup.exe"); 
                    ReadableByteChannel rbc = Channels.newChannel(website.openStream());
                    FileOutputStream fos = new FileOutputStream("setup.exe");
                    fos.getChannel().transferFrom(rbc, 0, 1 << 24);
                } catch (IOException exc) { 
                    System.out.println(exc);
                }   
            }   
        }.start();

    } else {
        // man
    }   
}

Java不喜欢下载文件。

3 个答案: