如何在翻转时更改JmenuItem的图标

Question

我想在我的JMenu中放置一个翻转效果，这是我的代码：

Icon firstPicAcc= new ImageIcon(Welcome.class.getResource("/app/resources/user1.jpg"));
    Icon secPicAcc= new  ImageIcon(Welcome.class.getResource("/app/resources/user2.jpg"));
    JMenu mnAccountSettings = new JMenu("Account Settings");
    mnAccountSettings.addMouseWheelListener(new MouseWheelListener() {
        public void mouseWheelMoved(MouseWheelEvent arg0) {
        }
    });

    mnAccountSettings.setFont(new Font("Dialog", Font.PLAIN, 20));
    mnAccountSettings.setForeground(new Color(0, 153, 0));
    mnAccountSettings.setBackground(new Color(255, 204, 255));
    mnAccountSettings.setRolloverEnabled(true);
    mnAccountSettings.setIcon(firstPicAcc);
    mnAccountSettings.setRolloverIcon(secPicAcc);

    mnAccount.add(mnAccountSettings);

我该怎么做？谢谢！ 应该发生的是当我将鼠标滚过JMenu栏时，原始图标应该变成另一个图标。

Answer 1

您要做的是向JMenuItem添加ChangeListener并检查它是selected还是armed并相应地更改icon。 ChangeListener适用于键盘和鼠标。

请参阅this good read by @kleopatra

private JMenuItem createMenuItem(final ImageIcon icon, String title) {
    JMenuItem item = new JMenuItem(title);
    item.setIcon(icon);

    ChangeListener cl = new ChangeListener() {

        @Override
        public void stateChanged(ChangeEvent e) {
            if (e.getSource() instanceof JMenuItem) {
                JMenuItem item = (JMenuItem) e.getSource();
                if (item.isSelected() || item.isArmed()) {
                    item.setIcon(stackIcon);
                } else {
                    item.setIcon(icon);
                }
            }
        }
    };
    item.addChangeListener(cl);

    return item;
}

这是运行示例。只需用你的图像替换图像

import java.awt.event.KeyEvent;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.SwingUtilities;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

public class RolloverMenuItem {
    ImageIcon stackIcon = new ImageIcon(getClass().getResource("/resources/stackoverflow2.png"));

    public RolloverMenuItem() {
        ImageIcon newIcon = new ImageIcon(getClass().getResource("/resources/image/new.gif"));
        ImageIcon saveIcon = new ImageIcon(getClass().getResource("/resources/image/open.gif"));
        ImageIcon openIcon = new ImageIcon(getClass().getResource("/resources/image/save.gif"));

        JMenu menu = new JMenu("File");
        menu.setMnemonic(KeyEvent.VK_F);
        JMenuItem item1 = createMenuItem(newIcon, "New");
        JMenuItem item2 = createMenuItem(openIcon, "Open");
        JMenuItem item3 = createMenuItem(saveIcon, "Save");
        menu.add(item1);
        menu.add(item2);
        menu.add(item3);

        JMenuBar menuBar = new JMenuBar();
        menuBar.add(menu);

        JFrame frame = new JFrame("Rollover MenuItem");
        frame.setJMenuBar(menuBar);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(400, 250);
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    private JMenuItem createMenuItem(final ImageIcon icon, String title) {
        JMenuItem item = new JMenuItem(title);
        item.setIcon(icon);

        ChangeListener cl = new ChangeListener() {

            @Override
            public void stateChanged(ChangeEvent e) {
                if (e.getSource() instanceof JMenuItem) {
                    JMenuItem item = (JMenuItem) e.getSource();
                    if (item.isSelected() || item.isArmed()) {
                        item.setIcon(stackIcon);
                    } else {
                        item.setIcon(icon);
                    }
                }
            }
        };
        item.addChangeListener(cl);

        return item;
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new RolloverMenuItem();
            }
        });
    }
}