test.java

swing 教程,与大家分享一下,哈哈,希望大家多多指教

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;

public class Test extends JApplet {
	public void init() {
		Container contentPane = getContentPane();
		JMenuBar menuBar = new JMenuBar();
		JMenu fileMenu = new JMenu("File");

		fileMenu.add(new UnderlineElement("item one"));
		fileMenu.add(new UnderlineElement("item two"));
		fileMenu.add(new UnderlineElement("item three"));

		menuBar.add(fileMenu);
		setJMenuBar(menuBar);
	}
}
class UnderlineElement extends JButton implements MenuElement {
	private boolean drawUnderline = false;

	public UnderlineElement(String s) {
		super(s);
		setBorder(BorderFactory.createEmptyBorder(2,2,2,2));
	}
	public Component getComponent() {
		return this;
	}
	public MenuElement[] getSubElements() {
		return new MenuElement[0];
	}
	public void menuSelectionChanged(boolean b) {
		drawUnderline = b;
		repaint();
	}
	public void paintComponent(Graphics g) {
		super.paintComponent(g);

		Insets insets = getInsets();

		if(drawUnderline) {
			FontMetrics fm = g.getFontMetrics();
			g.drawLine(insets.left, insets.top + fm.getHeight(),
					fm.stringWidth(getText()), 
					insets.top + fm.getHeight());
		}
	}
	public void processKeyEvent(KeyEvent me,
								MenuElement[] element, 
								MenuSelectionManager msm) {
	}
    public void processMouseEvent(MouseEvent me) {
		super.processMouseEvent(me);
		MenuSelectionManager.defaultManager().processMouseEvent(
															  me);
    }
	public void processMouseEvent(MouseEvent me, 
								MenuElement[] element, 
								MenuSelectionManager msm) {
		if(me.getID() == MouseEvent.MOUSE_CLICKED || 
		   me.getID() == MouseEvent.MOUSE_RELEASED) {

			msm.setSelectedPath(null);
			doClick();
		}
		else
			msm.setSelectedPath(getPath());
	}
    public MenuElement[] getPath() {
		MenuSelectionManager defaultManager = 
		MenuSelectionManager.defaultManager();
		MenuElement oldPath[] = defaultManager.getSelectedPath();
		MenuElement newPath[];
		int len = oldPath.length;

		if(len > 0) {
			MenuElement lastElement = oldPath[len-1];
			Component parent = getParent();

			if (lastElement == parent) {
				newPath = new MenuElement[len+1];

				System.arraycopy(oldPath, 0, newPath, 0, len);
				newPath[len] = this;
			}
			else {
				int j;

				for (j = len-1; j >= 0; j--) {
					if (oldPath[j].getComponent() == parent)
						break;
				}
				newPath = new MenuElement[j+2];
				System.arraycopy(oldPath, 0, newPath, 0, j+1);
				newPath[j+1] = this;
			}
		}
		else
			return new MenuElement[0];

		return newPath;
	}
}