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*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
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*
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* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
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*/
package components;
import java.awt.*;
import java.awt.event.*;
import javax.swing.JMenu;
import javax.swing.JMenuItem;
import javax.swing.JCheckBoxMenuItem;
import javax.swing.JRadioButtonMenuItem;
import javax.swing.ButtonGroup;
import javax.swing.JMenuBar;
import javax.swing.KeyStroke;
import javax.swing.ImageIcon;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.JScrollPane;
import javax.swing.JFrame;
/* MenuLookDemo.java requires images/middle.gif. */
/*
* This class exists solely to show you what menus look like.
* It has no menu-related event handling.
*/
public class MenuLookDemo {
JTextArea output;
JScrollPane scrollPane;
public JMenuBar createMenuBar() {
BackgroundMenuBar menuBar;
BackgroundMenu menu, submenu;
JMenuItem menuItem;
JRadioButtonMenuItem rbMenuItem;
JCheckBoxMenuItem cbMenuItem;
//Create the menu bar.
menuBar = new BackgroundMenuBar();
//Build the first menu.
menu = new BackgroundMenu("A Menu");
menu.setMnemonic(KeyEvent.VK_A);
menu.getAccessibleContext().setAccessibleDescription(
"The only menu in this program that has menu items");
menuBar.add(menu);
//a group of JMenuItems
menuItem = new JMenuItem("A text-only menu item",
KeyEvent.VK_T);
//menuItem.setMnemonic(KeyEvent.VK_T); //used constructor instead
menuItem.setAccelerator(KeyStroke.getKeyStroke(
KeyEvent.VK_1, ActionEvent.ALT_MASK));
menuItem.getAccessibleContext().setAccessibleDescription(
"This doesn't really do anything");
menu.add(menuItem);
ImageIcon icon = createImageIcon("images/middle.gif");
menuItem = new JMenuItem("Both text and icon", icon);
menuItem.setMnemonic(KeyEvent.VK_B);
menu.add(menuItem);
menuItem = new JMenuItem(icon);
menuItem.setMnemonic(KeyEvent.VK_D);
menu.add(menuItem);
//a group of radio button menu items
menu.addSeparator();
ButtonGroup group = new ButtonGroup();
rbMenuItem = new JRadioButtonMenuItem("A radio button menu item");
rbMenuItem.setSelected(true);
rbMenuItem.setMnemonic(KeyEvent.VK_R);
group.add(rbMenuItem);
menu.add(rbMenuItem);
rbMenuItem = new JRadioButtonMenuItem("Another one");
rbMenuItem.setMnemonic(KeyEvent.VK_O);
group.add(rbMenuItem);
menu.add(rbMenuItem);
//a group of check box menu items
menu.addSeparator();
cbMenuItem = new JCheckBoxMenuItem("A check box menu item");
cbMenuItem.setMnemonic(KeyEvent.VK_C);
menu.add(cbMenuItem);
cbMenuItem = new JCheckBoxMenuItem("Another one");
cbMenuItem.setMnemonic(KeyEvent.VK_H);
menu.add(cbMenuItem);
//a submenu
menu.addSeparator();
submenu = new BackgroundMenu("A submenu");
submenu.setMnemonic(KeyEvent.VK_S);
menuItem = new JMenuItem("An item in the submenu");
menuItem.setAccelerator(KeyStroke.getKeyStroke(
KeyEvent.VK_2, ActionEvent.ALT_MASK));
submenu.add(menuItem);
menuItem = new JMenuItem("Another item");
submenu.add(menuItem);
menu.add(submenu);
//Build second menu in the menu bar.
menu = new BackgroundMenu("Another Menu");
menu.setMnemonic(KeyEvent.VK_N);
menu.getAccessibleContext().setAccessibleDescription(
"This menu does nothing");
menuBar.add(menu);
return menuBar;
}
public Container createContentPane() {
//Create the content-pane-to-be.
JPanel contentPane = new JPanel(new BorderLayout());
contentPane.setOpaque(true);
//Create a scrolled text area.
output = new JTextArea(5, 30);
output.setEditable(false);
scrollPane = new JScrollPane(output);
//Add the text area to the content pane.
contentPane.add(scrollPane, BorderLayout.CENTER);
return contentPane;
}
/** Returns an ImageIcon, or null if the path was invalid. */
protected static ImageIcon createImageIcon(String path) {
java.net.URL imgURL = MenuLookDemo.class.getResource(path);
if (imgURL != null) {
return new ImageIcon(imgURL);
} else {
System.err.println("Couldn't find file: " + path);
return null;
}
}
/**
* Create the GUI and show it. For thread safety,
* this method should be invoked from the
* event-dispatching thread.
*/
private static void createAndShowGUI() {
//Create and set up the window.
JFrame frame = new JFrame("MenuLookDemo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//Create and set up the content pane.
MenuLookDemo demo = new MenuLookDemo();
frame.setJMenuBar(demo.createMenuBar());
frame.setContentPane(demo.createContentPane());
//Display the window.
frame.setSize(450, 260);
frame.setVisible(true);
}
public static void main(String[] args) {
//Schedule a job for the event-dispatching thread:
//creating and showing this application's GUI.
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}
class BackgroundMenuBar extends JMenuBar
{
Color bgColor=Color.BLUE;
public void setColor(Color color)
{
bgColor=color;
}
@Override
protected void paintComponent(Graphics g)
{
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setColor(bgColor);
g2d.fillRect(0, 0, getWidth() - 1, getHeight() - 1);
}
}
class BackgroundMenu extends JMenu
{
Color bgColor=Color.BLUE;
public BackgroundMenu(String s){
super(s);
}
public void setColor(Color color)
{
bgColor=color;
}
@Override
protected void paintComponent(Graphics g)
{
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setColor(bgColor);
g2d.fillRect(0, 0, getWidth() - 1, getHeight() - 1);
}
}
关键代码：
class BackgroundMenuBar extends JMenuBar
{
Color bgColor=Color.BLUE;
public void setColor(Color color)
{
bgColor=color;
}
@Override
protected void paintComponent(Graphics g)
{
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setColor(bgColor);
g2d.fillRect(0, 0, getWidth() - 1, getHeight() - 1);
}
}
class BackgroundMenu extends JMenu
{
Color bgColor=Color.BLUE;
public BackgroundMenu(String s){
super(s);
}
public void setColor(Color color)
{
bgColor=color;
}
@Override
protected void paintComponent(Graphics g)
{
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setColor(bgColor);
g2d.fillRect(0, 0, getWidth() - 1, getHeight() - 1);
}
}
追问一点注释都没有，太难懂了
追答class BackgroundMenuBar extends JMenuBar
{
Color bgColor=Color.BLUE;
public void setColor(Color color)
{
bgColor=color;
}
@Override
protected void paintComponent(Graphics g)
{
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setColor(bgColor);
g2d.fillRect(0, 0, getWidth() - 1, getHeight() - 1);
}
}
你要继承JMenuBar，实例化BackgroundMenuBar，而不是JMenuBar
bgColor=color;
设置颜色