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java - JDialog 和 Thread 的 ClassCastException

转载 作者：塔克拉玛干 更新时间：2023-11-02 07:58:19 24 4
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我有一个带有线程的 JDialog。它偶尔会在创建对话框时给我一个 ClassCastException(这意味着我可以无一异常(exception)地成功)，而且我不知道它应该在哪里发生。

这是我的 JDialog 类的一个片段

public class ConfirmExitDialog extends JDialog implements Runnable,
    ActionListener {
private static final long serialVersionUID = -8762051370686039110L;
private Thread dialogThread;
private boolean running;
private int result, count = 60;
private HandleExit  handleExit = null;

// GUI
private JOptionPane optionPane;
private JLabel msgLabel = new JLabel();
private JButton btnYes;
private JButton btnNo;

private void updateLabelText() {
    msgLabel.setText("<html>Ønsker du at afslutte dagens salg?<br>Programmet afslutter automatisk om " + count + " sekunder.</html>");
}

public int getResult() {
    return result;
}

public ConfirmExitDialog(Frame frame, HandleExit handleExit) {
    super(frame, false);
    this.handleExit = handleExit;

    setTitle("Afslut dagens salg?");
    display();

    running = true;
    if (dialogThread == null) {
        dialogThread = new Thread(this, "ConfirmExitDialog");
        dialogThread.start();
    }
    this.setModal(true);
}

public void close() {
    if (dialogThread != null)
        running = false;
}

private void display() {
    setLayout(new BorderLayout());

    // Buttons
    btnYes = new JButton("Ja");
    btnYes.addActionListener(this);
    btnYes.setMnemonic('J');
    add(btnYes, BorderLayout.WEST);
    btnNo = new JButton("Nej");
    btnNo.addActionListener(this);
    btnNo.setMnemonic('N');
    add(btnNo, BorderLayout.EAST);
    JButton[] buttons = { btnYes, btnNo };

    updateLabelText();
    optionPane = new JOptionPane(msgLabel, JOptionPane.QUESTION_MESSAGE,
            JOptionPane.YES_NO_OPTION, null, buttons, buttons[0]);
    setContentPane(optionPane);

    setDefaultCloseOperation(DISPOSE_ON_CLOSE);

    // Handle window closing correctly.
    setDefaultCloseOperation(DO_NOTHING_ON_CLOSE);
    addWindowListener(new WindowAdapter() {
      public void windowClosing(WindowEvent we) {
        /*
         * Instead of directly closing the window, we're going to change the
         * JOptionPane's value property.
         */
        optionPane.setValue(new Integer(JOptionPane.CLOSED_OPTION));
      }
    });

    pack();
    setVisible(true);   
}

private void countDown() {
    updateLabelText();
    count--;
}

@Override
public void run() {
    // TODO Auto-generated method stub

    try {
        display();
        while (running && count > 0) {
            System.out.println("Countdown " + count);
            pack();
            countDown();
            Thread.sleep(1000);
        }

        setVisible(false);
        if (count == 0)
            handleExit.closeApplication(true, true);


    } catch (InterruptedException ie) {
        // Thread stopped
    }
}

@Override
public void actionPerformed(ActionEvent event) {
    Object src = event.getSource();

    if (src == btnYes) {
        setVisible(false);
        result = JOptionPane.YES_OPTION;
        running = false;
        handleExit.closeApplication(true, false);
    }
    if (src == btnNo) {
        setVisible(false);
        result = JOptionPane.NO_OPTION;
        running = false;

    }
}

这是异常转换:

Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException at javax.swing.LayoutComparator.compare(LayoutComparator.java:61) at java.util.Arrays.mergeSort(Arrays.java:1293) at java.util.Arrays.mergeSort(Arrays.java:1282) at java.util.Arrays.sort(Arrays.java:1210) at java.util.Collections.sort(Collections.java:159) at javax.swing.SortingFocusTraversalPolicy.enumerateAndSortCycle(SortingFocusTraversalPolicy.java:119) at javax.swing.SortingFocusTraversalPolicy.getFirstComponent(SortingFocusTraversalPolicy.java:434) at javax.swing.LayoutFocusTraversalPolicy.getFirstComponent(LayoutFocusTraversalPolicy.java:148) at javax.swing.SortingFocusTraversalPolicy.getDefaultComponent(SortingFocusTraversalPolicy.java:511) at java.awt.FocusTraversalPolicy.getInitialComponent(FocusTraversalPolicy.java:152) at java.awt.Window.getMostRecentFocusOwner(Window.java:2131) at java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFocusManager.java:629) at java.awt.Component.dispatchEventImpl(Component.java:4502) at java.awt.Container.dispatchEventImpl(Container.java:2099) at java.awt.Window.dispatchEventImpl(Window.java:2478) at java.awt.Component.dispatchEvent(Component.java:4460) at java.awt.EventQueue.dispatchEvent(EventQueue.java:599) at java.awt.SequencedEvent.dispatch(SequencedEvent.java:101) at java.awt.EventQueue.dispatchEvent(EventQueue.java:597) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161) at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

谢谢。丹尼尔

最佳答案

强烈建议不要在 Swing 的 EventDispatchThread 以外的线程中修改 UI，因为它可能而且会导致奇怪的副作用(就像您遇到的那样)。

想象一下 UI 即将重新绘制自身(和布局内容)，而您只是通过使用另一个线程同时更改 UI 的某些部分来进行干预。在这种情况下，很可能会发生困惑。

有关详细信息，请参阅 Java 教程类(class) Concurrency in Swing

处理此问题的正确方法是让后台线程执行任何与 UI 无关的工作，并在 EventDispatchThread 中安排一个 UI 更新作业(它将在处理事件之间执行该作业)。

例子:

    Thread t = new Thread() {

        public void run () {

            // do background work

            SwingUtilities.invokeLater(new Runnable() {

                public void run () {
                    // update UI parts
                }
            });
        }
    };
    t.start();

SwingUtilities.invokeLater(Runnnable) 将安排一个 Runnable 供稍后执行，而SwingUtilities.invokeAndWait(Runnnable) 将安排一个 Runnable 并等待它执行。

关于java - JDialog 和 Thread 的 ClassCastException，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/2966552/

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