Java/Swing+NetBeans 6.1。键盘事件不起作用

Question

我需要在窗体上移动标签控件。

我在 NetBeans 6.1 中创建了一个“Java 桌面应用程序”。

我添加了以下代码：

但标签没有移动。

为什么？

/*
 * DesktopApplication1View.java
 */

package desktopapplication1;

import org.jdesktop.application.Action;
import org.jdesktop.application.ResourceMap;
import org.jdesktop.application.SingleFrameApplication;
import org.jdesktop.application.FrameView;
import org.jdesktop.application.TaskMonitor;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import javax.swing.Timer;
import javax.swing.Icon;
import javax.swing.JDialog;
import javax.swing.JFrame;

/**
 * The application's main frame.
 */
public class DesktopApplication1View extends FrameView {

    public DesktopApplication1View(SingleFrameApplication app) 
    {
        super(app);

        initComponents();

        // status bar initialization - message timeout, idle icon and busy animation, etc
        ResourceMap resourceMap = getResourceMap();
        int messageTimeout = resourceMap.getInteger("StatusBar.messageTimeout");
        messageTimer = new Timer(messageTimeout, new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                statusMessageLabel.setText("");
            }
        });
        messageTimer.setRepeats(false);
        int busyAnimationRate = resourceMap.getInteger("StatusBar.busyAnimationRate");
        for (int i = 0; i < busyIcons.length; i++) {
            busyIcons[i] = resourceMap.getIcon("StatusBar.busyIcons[" + i + "]");
        }
        busyIconTimer = new Timer(busyAnimationRate, new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                busyIconIndex = (busyIconIndex + 1) % busyIcons.length;
                statusAnimationLabel.setIcon(busyIcons[busyIconIndex]);
            }
        });
        idleIcon = resourceMap.getIcon("StatusBar.idleIcon");
        statusAnimationLabel.setIcon(idleIcon);
        progressBar.setVisible(false);

        // connecting action tasks to status bar via TaskMonitor
        TaskMonitor taskMonitor = new TaskMonitor(getApplication().getContext());
        taskMonitor.addPropertyChangeListener(new java.beans.PropertyChangeListener() {
            public void propertyChange(java.beans.PropertyChangeEvent evt) {
                String propertyName = evt.getPropertyName();
                if ("started".equals(propertyName)) {
                    if (!busyIconTimer.isRunning()) {
                        statusAnimationLabel.setIcon(busyIcons[0]);
                        busyIconIndex = 0;
                        busyIconTimer.start();
                    }
                    progressBar.setVisible(true);
                    progressBar.setIndeterminate(true);
                } else if ("done".equals(propertyName)) {
                    busyIconTimer.stop();
                    statusAnimationLabel.setIcon(idleIcon);
                    progressBar.setVisible(false);
                    progressBar.setValue(0);
                } else if ("message".equals(propertyName)) {
                    String text = (String)(evt.getNewValue());
                    statusMessageLabel.setText((text == null) ? "" : text);
                    messageTimer.restart();
                } else if ("progress".equals(propertyName)) {
                    int value = (Integer)(evt.getNewValue());
                    progressBar.setVisible(true);
                    progressBar.setIndeterminate(false);
                    progressBar.setValue(value);
                }
            }
        });

        jLabel1.isOptimizedDrawingEnabled();
        jLabel1.requestFocusInWindow();
    }

    @Action
    public void showAboutBox() {
        if (aboutBox == null) {
            JFrame mainFrame = DesktopApplication1.getApplication().getMainFrame();
            aboutBox = new DesktopApplication1AboutBox(mainFrame);
            aboutBox.setLocationRelativeTo(mainFrame);
        }
        DesktopApplication1.getApplication().show(aboutBox);
    }

    /** This method is called from within the constructor to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">
    private void initComponents() {

        mainPanel = new javax.swing.JPanel();
        jLabel1 = new javax.swing.JLabel();
        menuBar = new javax.swing.JMenuBar();
        javax.swing.JMenu fileMenu = new javax.swing.JMenu();
        javax.swing.JMenuItem exitMenuItem = new javax.swing.JMenuItem();
        javax.swing.JMenu helpMenu = new javax.swing.JMenu();
        javax.swing.JMenuItem aboutMenuItem = new javax.swing.JMenuItem();
        statusPanel = new javax.swing.JPanel();
        javax.swing.JSeparator statusPanelSeparator = new javax.swing.JSeparator();
        statusMessageLabel = new javax.swing.JLabel();
        statusAnimationLabel = new javax.swing.JLabel();
        progressBar = new javax.swing.JProgressBar();

        mainPanel.setName("mainPanel"); // NOI18N

        org.jdesktop.application.ResourceMap resourceMap = org.jdesktop.application.Application.getInstance(desktopapplication1.DesktopApplication1.class).getContext().getResourceMap(DesktopApplication1View.class);
        jLabel1.setText(resourceMap.getString("jLabel1.text")); // NOI18N
        jLabel1.setName("jLabel1"); // NOI18N
        jLabel1.addKeyListener(new java.awt.event.KeyAdapter() {
            public void keyPressed(java.awt.event.KeyEvent evt) {
                jLabel1KeyPressed(evt);
            }
        });

        javax.swing.GroupLayout mainPanelLayout = new javax.swing.GroupLayout(mainPanel);
        mainPanel.setLayout(mainPanelLayout);
        mainPanelLayout.setHorizontalGroup(
            mainPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(mainPanelLayout.createSequentialGroup()
                .addGap(151, 151, 151)
                .addComponent(jLabel1)
                .addContainerGap(215, Short.MAX_VALUE))
        );
        mainPanelLayout.setVerticalGroup(
            mainPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(mainPanelLayout.createSequentialGroup()
                .addGap(83, 83, 83)
                .addComponent(jLabel1)
                .addContainerGap(155, Short.MAX_VALUE))
        );

        menuBar.setName("menuBar"); // NOI18N

        fileMenu.setText(resourceMap.getString("fileMenu.text")); // NOI18N
        fileMenu.setName("fileMenu"); // NOI18N

        javax.swing.ActionMap actionMap = org.jdesktop.application.Application.getInstance(desktopapplication1.DesktopApplication1.class).getContext().getActionMap(DesktopApplication1View.class, this);
        exitMenuItem.setAction(actionMap.get("quit")); // NOI18N
        exitMenuItem.setName("exitMenuItem"); // NOI18N
        fileMenu.add(exitMenuItem);

        menuBar.add(fileMenu);

        helpMenu.setText(resourceMap.getString("helpMenu.text")); // NOI18N
        helpMenu.setName("helpMenu"); // NOI18N

        aboutMenuItem.setAction(actionMap.get("showAboutBox")); // NOI18N
        aboutMenuItem.setName("aboutMenuItem"); // NOI18N
        helpMenu.add(aboutMenuItem);

        menuBar.add(helpMenu);

        statusPanel.setName("statusPanel"); // NOI18N

        statusPanelSeparator.setName("statusPanelSeparator"); // NOI18N

        statusMessageLabel.setName("statusMessageLabel"); // NOI18N

        statusAnimationLabel.setHorizontalAlignment(javax.swing.SwingConstants.LEFT);
        statusAnimationLabel.setName("statusAnimationLabel"); // NOI18N

        progressBar.setName("progressBar"); // NOI18N

        javax.swing.GroupLayout statusPanelLayout = new javax.swing.GroupLayout(statusPanel);
        statusPanel.setLayout(statusPanelLayout);
        statusPanelLayout.setHorizontalGroup(
            statusPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(statusPanelSeparator, javax.swing.GroupLayout.DEFAULT_SIZE, 400, Short.MAX_VALUE)
            .addGroup(statusPanelLayout.createSequentialGroup()
                .addContainerGap()
                .addComponent(statusMessageLabel)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 226, Short.MAX_VALUE)
                .addComponent(progressBar, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(statusAnimationLabel)
                .addContainerGap())
        );
        statusPanelLayout.setVerticalGroup(
            statusPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(statusPanelLayout.createSequentialGroup()
                .addComponent(statusPanelSeparator, javax.swing.GroupLayout.PREFERRED_SIZE, 2, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addGroup(statusPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(statusMessageLabel)
                    .addComponent(statusAnimationLabel)
                    .addComponent(progressBar, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(3, 3, 3))
        );

        setComponent(mainPanel);
        setMenuBar(menuBar);
        setStatusBar(statusPanel);
    }// </editor-fold>

private void jLabel1KeyPressed(java.awt.event.KeyEvent evt) {                                   
// TODO add your handling code here:
    int keyCode = evt.getKeyCode();
    int xPos = jLabel1.getX();
    int yPos = jLabel1.getY();    

    switch(keyCode)
    {
        case  KeyEvent.VK_UP:
            jLabel1.setLocation(xPos, --yPos);
            break;

        case  KeyEvent.VK_DOWN:
            jLabel1.setLocation(xPos, ++yPos);
            break;

        case  KeyEvent.VK_LEFT:
            jLabel1.setLocation(--xPos, yPos);
            break;

        case  KeyEvent.VK_RIGHT:
            jLabel1.setLocation(++xPos, yPos);
            break;
    }
}                                  

    // Variables declaration - do not modify
    private javax.swing.JLabel jLabel1;
    private javax.swing.JPanel mainPanel;
    private javax.swing.JMenuBar menuBar;
    private javax.swing.JProgressBar progressBar;
    private javax.swing.JLabel statusAnimationLabel;
    private javax.swing.JLabel statusMessageLabel;
    private javax.swing.JPanel statusPanel;
    // End of variables declaration

    private final Timer messageTimer;
    private final Timer busyIconTimer;
    private final Icon idleIcon;
    private final Icon[] busyIcons = new Icon[15];
    private int busyIconIndex = 0;

    private JDialog aboutBox;
}

Answer 1

查看 Swing 教程。

1) 只有获得焦点的组件才能接收KeyEvents。默认情况下，JLabel 不可聚焦，因此它永远不会接收 KeyEvent。更好的方法是使用键绑定。请参阅 Swing 教程中有关键绑定的部分。

2) 如果修复 1，则标签可能会移动，但如果调整框架大小，标签不会停留在新位置，因为将调用布局管理器并根据其规则重新定位标签。

阅读 Swing 教程中有关使用布局管理器的部分。如果您确实需要将标签置于随机位置，那么您将需要使用绝对定位，本教程中也对此进行了讨论。