如上所述，您将使用 JDialog，这是一个易于制作（类似于制作 JFrame）且易于放置的组件。只需将其“相对于”JFrame，例如，
myDialog.setLocationRelativeTo(myJFrame);
... 它会自动以 JFrame 为中心。棘手的部分是使底层 JFrame 变暗，为此，您需要使用添加到 JFrame 根窗格的 JGlassPane，一组具有使用 alpha 复合值的背景颜色。棘手的部分是在不引起副作用的情况下绘制较暗的背景，为此，请阅读 Rob Camick（StackOverflow 用户camickr）关于使用 alpha 复合材料在 Swing 中绘制的优秀教程，您可以在此处找到：Java Tips Weblog: Backgrounds with Transparency
此处显示了此类程序的示例：
import java.awt.Color;
import java.awt.Component;
import java.awt.Dialog.ModalityType;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.awt.Window;
import java.awt.event.ActionEvent;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.swing.*;
public class DialogEg {
// path to example image used as "game" background
private static final String IMG_PATH = "https://upload.wikimedia.org/"
+ "wikipedia/commons/7/76/Jump_%27n_Bump.png";
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> createAndShowGui());
}
private static void createAndShowGui() {
// get the "game" background image, or exit if fail
BufferedImage img = null;
try {
URL imgUrl = new URL(IMG_PATH);
img = ImageIO.read(imgUrl);
} catch (IOException e) {
e.printStackTrace();
System.exit(-1);
}
// pass "game" image into main JPanel so that it will be drawn
DeMainPanel mainPanel = new DeMainPanel(img);
JFrame frame = new JFrame("Dialog Example");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.add(mainPanel); // add main JPanel to JFrame
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
}
// main JPanel
@SuppressWarnings("serial")
class DeMainPanel extends JPanel {
private BufferedImage img; // background image
// JButton action that shows the JDialog and darkens the glasspane
private PauseAction pauseAction = new PauseAction("Pause");
public DeMainPanel(BufferedImage img) {
super();
this.img = img;
add(new JButton(pauseAction));
}
// draw the "game" background image within the JPanel if not null
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (img != null) {
g.drawImage(img, 0, 0, this);
}
}
// size this JPanel to match the image's size
@Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet() || img == null) {
return super.getPreferredSize();
}
int width = img.getWidth();
int height = img.getHeight();
return new Dimension(width, height);
}
}
// Action / ActionListener for JButton -- shows JDialog and darkens glasspane
@SuppressWarnings("serial")
class PauseAction extends AbstractAction {
private static final int ALPHA = 175; // how much see-thru. 0 to 255
private static final Color GP_BG = new Color(0, 0, 0, ALPHA);
private DeDialogPanel deDialogPanel = new DeDialogPanel(); // jpanel shown in JDialog
public PauseAction(String name) {
super(name);
}
@Override
public void actionPerformed(ActionEvent e) {
// comp is our JButton
Component comp = (Component) e.getSource();
if (comp == null) {
return;
}
// create our glass pane
JPanel glassPane = new JPanel() {
@Override
protected void paintComponent(Graphics g) {
// magic to make it dark without side-effects
g.setColor(getBackground());
g.fillRect(0, 0, getWidth(), getHeight());
super.paintComponent(g);
}
};
// more magic below
glassPane.setOpaque(false);
glassPane.setBackground(GP_BG);
// get the rootpane container, here the JFrame, that holds the JButton
RootPaneContainer win = (RootPaneContainer) SwingUtilities.getWindowAncestor(comp);
win.setGlassPane(glassPane); // set the glass pane
glassPane.setVisible(true); // and show the glass pane
// create a *modal* JDialog
JDialog dialog = new JDialog((Window)win, "", ModalityType.APPLICATION_MODAL);
dialog.getContentPane().add(deDialogPanel); // add its JPanel to it
dialog.setUndecorated(true); // give it no borders (if desired)
dialog.pack(); // size it
dialog.setLocationRelativeTo((Window) win); // ** Center it over the JFrame **
dialog.setVisible(true); // display it, pausing the GUI below it
// at this point the dialog is no longer visible, so get rid of glass pane
glassPane.setVisible(false);
}
}
// JPanel shown in the modal JDialog above
@SuppressWarnings("serial")
class DeDialogPanel extends JPanel {
private static final Color BG = new Color(123, 63, 0);
public DeDialogPanel() {
JLabel pausedLabel = new JLabel("PAUSED");
pausedLabel.setForeground(Color.ORANGE);
JPanel pausedPanel = new JPanel();
pausedPanel.setOpaque(false);
pausedPanel.add(pausedLabel);
setBackground(BG);
int eb = 15;
setBorder(BorderFactory.createEmptyBorder(eb, eb, eb, eb));
setLayout(new GridLayout(0, 1, 10, 10));
add(pausedPanel);
add(new JButton(new FooAction("RESUME")));
add(new JButton(new FooAction("RESTART")));
add(new JButton(new FooAction("EXIT TO MAP")));
}
// simple action -- all it does is to make the dialog no longer visible
private class FooAction extends AbstractAction {
public FooAction(String name) {
super(name);
}
@Override
public void actionPerformed(ActionEvent e) {
Component comp = (Component) e.getSource();
Window win = SwingUtilities.getWindowAncestor(comp);
win.dispose(); // here -- dispose of the JDialog
}
}
}
GUI 最初看起来像这样：
但是当对话框显示并且玻璃窗格变暗时，它看起来像这样：