对于一个项目，我们想要创建一个按钮，当它被点击时会产生一个小菜单（它的工作方式类似于Firefox中的后退按钮的下拉菜单，尽管激活的方法是简单的左键单击）。唯一真正的限制是它必须是Java（如果可能的话，最好是摆动）。那么，任何想法，例子，代码如何做到这一点？
使用JPopupMenu。例如。
import java.awt.event.*;
import javax.swing.*;
class PopUpMenuDemo {
public static void main(String[] args) {
Runnable r = new Runnable() {
public void run() {
final JButton b = new JButton("Pop Up");
final JPopupMenu menu = new JPopupMenu("Menu");
menu.add("A");
menu.add("B");
menu.add("C");
b.addActionListener( new ActionListener() {
public void actionPerformed(ActionEvent ae) {
menu.show(b, b.getWidth()/2, b.getHeight()/2);
}
} );
JOptionPane.showMessageDialog(null,b);
}
};
SwingUtilities.invokeLater(r);
}
}
我可能会这样做：
frame = new JFrame();
frame.setBounds(100, 100, 450, 300);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().setLayout(null);
JButton btnClickMe = new JButton("Click me");
btnClickMe.setBounds(10, 30, 89, 23);
frame.getContentPane().add(btnClickMe);
final JPopupMenu menu = new JPopupMenu();
JMenuItem item1 = new JMenuItem("Item1");
JMenuItem item2 = new JMenuItem("Item2");
JMenuItem item3 = new JMenuItem("Item3");
menu.add(item1);
menu.add(item2);
menu.add(item3);
btnClickMe.addMouseListener(new MouseAdapter() {
public void mouseReleased(MouseEvent e){
if ( e.getButton() == 1 ){ // 1-left, 2-middle, 3-right button
menu.show(e.getComponent(), e.getX(), e.getY());
}
}
});
这是menuButton的代码，它看起来像一个按钮，当你点击它时会出现一个菜单。您可以通过将图像图标添加到菜单并通过以下方法来自定义它：
setFocusable(false);
setBorderPainted(false);
setOpaque(false);
如果你想像FireFox那样设置它，然后设置菜单的图标并调用上面的方法，然后设置翻转图标，选择图标和翻转选择图标。
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
class menuButton extends JFrame
{
JMenuBar fileMenuBar,editMenuBar;
JMenu fileMenu,editMenu;
JMenuItem newFile,open,save,saveas,exit;
JMenuItem cut,copy,paste,undo,redo;
public menuButton()
{
setTitle("menu Button");
setSize(500,500);
setLayout(new FlowLayout());
setDefaultCloseOperation(EXIT_ON_CLOSE);
setVisible(true);
fileMenuBar=new JMenuBar();
editMenuBar=new JMenuBar();
fileMenu=new JMenu("File");
editMenu=new JMenu("Edit");
newFile=new JMenuItem("New");
newFile.setAccelerator(KeyStroke.getKeyStroke('N',InputEvent.CTRL_MASK));
open=new JMenuItem("Open");
open.setAccelerator(KeyStroke.getKeyStroke('O',InputEvent.CTRL_MASK));
save=new JMenuItem("Save");
save.setAccelerator(KeyStroke.getKeyStroke('S',InputEvent.CTRL_MASK));
saveas=new JMenuItem("Save As");
saveas.setAccelerator(KeyStroke.getKeyStroke('A',InputEvent.CTRL_MASK));
exit=new JMenuItem("Exit");
exit.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_F4,InputEvent.ALT_MASK));
cut=new JMenuItem("Cut");
cut.setAccelerator(KeyStroke.getKeyStroke('X',InputEvent.CTRL_MASK));
copy=new JMenuItem("Copy");
copy.setAccelerator(KeyStroke.getKeyStroke('C',InputEvent.CTRL_MASK));
paste=new JMenuItem("Paste");
paste.setAccelerator(KeyStroke.getKeyStroke('V',InputEvent.CTRL_MASK));
undo=new JMenuItem("Undo");
undo.setAccelerator(KeyStroke.getKeyStroke('Z',InputEvent.CTRL_MASK));
redo=new JMenuItem("Redo");
redo.setAccelerator(KeyStroke.getKeyStroke('R',InputEvent.CTRL_MASK));
editMenu.add(cut);
editMenu.add(copy);
editMenu.add(paste);
editMenu.addSeparator();
editMenu.add(undo);
editMenu.add(redo);
fileMenu.add(newFile);
fileMenu.add(open);
fileMenu.add(save);
fileMenu.add(saveas);
fileMenu.add(exit);
fileMenuBar.add(fileMenu);
editMenuBar.add(editMenu);
add(fileMenuBar);
add(editMenuBar);
}
public static void main(String args[])
{
new menuButton();
}
}
看到这个可能会对你有所帮助
import java.io.*;
import java.net.*;
import java.awt.*;
import java.awt.geom.*;
import java.awt.event.*;
import java.awt.image.*;
import javax.swing.*;
public class GUI implements ActionListener, MouseListener, MouseMotionListener, KeyListener {
private final BufferedImage offscreenImage; // double buffered image
private final BufferedImage onscreenImage; // double buffered image
private final Graphics2D offscreen;
private final Graphics2D onscreen;
private JFrame frame; // the top-level component
private JPanel center = new JPanel(); // center panel
// create a GUI with a menu, some buttons, and a drawing window of size width-by-height
public GUI(int width, int height) {
offscreenImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
onscreenImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
offscreen = (Graphics2D) offscreenImage.getGraphics();
onscreen = (Graphics2D) onscreenImage.getGraphics();
// the drawing panel
ImageIcon icon = new ImageIcon(onscreenImage);
JLabel draw = new JLabel(icon);
draw.addMouseListener(this);
draw.addMouseMotionListener(this);
// label cannot get keyboard focus
center.add(draw);
center.addKeyListener(this);
// west panel of buttons
JPanel west = new JPanel();
west.setLayout(new BoxLayout(west, BoxLayout.PAGE_AXIS));
JButton button1 = new JButton("button 1");
JButton button2 = new JButton("button 2");
JButton button3 = new JButton("button 3");
JButton button4 = new JButton("button 4");
button1.addActionListener(this);
button2.addActionListener(this);
button3.addActionListener(this);
button4.addActionListener(this);
button1.setToolTipText("Click me");
west.add(button1);
west.add(button2);
west.add(button3);
west.add(button4);
// menu
JMenuBar menuBar = new JMenuBar();
JMenu menu = new JMenu("File");
menuBar.add(menu);
JMenuItem menuSave = new JMenuItem(" Save... ");
menuSave.addActionListener(this);
menuSave.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_S, Toolkit.getDefaultToolkit().getMenuShortcutKeyMask()));
menu.add(menuSave);
// setup the frame and add components
frame = new JFrame();
frame.setJMenuBar(menuBar);
frame.add(west, BorderLayout.WEST);
frame.add(center, BorderLayout.CENTER);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setResizable(false);
frame.pack();
// give the focus to the center panel
center.requestFocusInWindow();
frame.setVisible(true);
}
// draw picture (gif, jpg, or png) centered on (x, y)
public void picture(int x, int y, String filename) {
ImageIcon icon = new ImageIcon(filename);
Image image = icon.getImage();
offscreen.drawImage(image, x, y, null);
show();
}
// display the drawing canvas on the screen
public void show() {
onscreen.drawImage(offscreenImage, 0, 0, null);
frame.repaint();
}
/*************************************************************************
* Event callbacks
*************************************************************************/
// for buttons and menus
public void actionPerformed(ActionEvent e) {
Object cmd = e.getActionCommand();
if (cmd.equals(" Save... ")) System.out.println("File -> Save");
else if (cmd.equals("button 1")) System.out.println("Button 1 pressed");
else if (cmd.equals("button 2")) System.out.println("Button 2 pressed");
else if (cmd.equals("button 3")) System.out.println("Button 3 pressed");
else if (cmd.equals("button 4")) System.out.println("Button 4 pressed");
else System.out.println("Unknown action");
// don't hog the keyboard focus
center.requestFocusInWindow();
}
// for the mouse
public void mousePressed(MouseEvent e) {
int x = e.getX();
int y = e.getY();
System.out.println("Mouse pressed at " + x + ", " + y);
offscreen.setColor(Color.BLUE);
offscreen.fillOval(x-3, y-3, 6, 6);
show();
}
public void mouseClicked (MouseEvent e) { }
public void mouseReleased(MouseEvent e) { }
public void mouseEntered (MouseEvent e) { }
public void mouseExited (MouseEvent e) { }
public void mouseDragged (MouseEvent e) { }
public void mouseMoved (MouseEvent e) { }
// for the keyboard
public void keyPressed (KeyEvent e) { }
public void keyReleased(KeyEvent e) { }
public void keyTyped(KeyEvent e) {
System.out.println("Key = '" + e.getKeyChar() + "'");
}
// test client
public static void main(String[] args) {
GUI gui = new GUI(800, 471);
gui.picture(0, 0, "map.png");
gui.show();
}
}
如果您喜欢代码中的较小代码行，请尝试以下代码：
在您的按钮内部actionPerformed：
private void yourButtonActionPerformed(java.awt.event.ActionEvent evt) {
final JPopupMenu yourMenu = new JPopupMenu("Settings");
menu.add("Name");
menu.add("Id");
menu.add(new Button()); // can even add buttons and other components as well.
menu.show(yourButton, yourButton.getWidth()/2, yourButton.getHeight()/2);
}