Java Tutorials Code Sample – GlassPaneDemo.java

package components;
import javax.swing.*;
import java.awt.*;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.awt.event.MouseEvent;
import javax.swing.event.MouseInputAdapter;
/** An application that requires no other files. */
public class GlassPaneDemo {
    static private MyGlassPane myGlassPane;
    /**
     * 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("GlassPaneDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        //Start creating and adding components.
        JCheckBox changeButton =
                new JCheckBox("Glass pane \"visible\"");
        changeButton.setSelected(false);
        
        //Set up the content pane, where the "main GUI" lives.
        Container contentPane = frame.getContentPane();
        contentPane.setLayout(new FlowLayout());
        contentPane.add(changeButton);
        contentPane.add(new JButton("Button 1"));
        contentPane.add(new JButton("Button 2"));
        //Set up the menu bar, which appears above the content pane.
        JMenuBar menuBar = new JMenuBar();
        JMenu menu = new JMenu("Menu");
        menu.add(new JMenuItem("Do nothing"));
        menuBar.add(menu);
        frame.setJMenuBar(menuBar);
        //Set up the glass pane, which appears over both menu bar
        //and content pane and is an item listener on the change
        //button.
        myGlassPane = new MyGlassPane(changeButton, menuBar,
                                      frame.getContentPane());
        changeButton.addItemListener(myGlassPane);
        frame.setGlassPane(myGlassPane);
        //Show the window.
        frame.pack();
        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();
            }
        });
    }
}
/**
 * We have to provide our own glass pane so that it can paint.
 */
class MyGlassPane extends JComponent
                  implements ItemListener {
    Point point;
    //React to change button clicks.
    public void itemStateChanged(ItemEvent e) {
        setVisible(e.getStateChange() == ItemEvent.SELECTED);
    }
    protected void paintComponent(Graphics g) {
        if (point != null) {
            g.setColor(Color.red);
            g.fillOval(point.x - 10, point.y - 10, 20, 20);
        }
    }
    public void setPoint(Point p) {
        point = p;
    }
    public MyGlassPane(AbstractButton aButton,
                       JMenuBar menuBar,
                       Container contentPane) {
        CBListener listener = new CBListener(aButton, menuBar,
                                             this, contentPane);
        addMouseListener(listener);
        addMouseMotionListener(listener);
    }
}
/**
 * Listen for all events that our check box is likely to be
 * interested in.  Redispatch them to the check box.
 */
class CBListener extends MouseInputAdapter {
    Toolkit toolkit;
    Component liveButton;
    JMenuBar menuBar;
    MyGlassPane glassPane;
    Container contentPane;
    public CBListener(Component liveButton, JMenuBar menuBar,
                      MyGlassPane glassPane, Container contentPane) {
        toolkit = Toolkit.getDefaultToolkit();
        this.liveButton = liveButton;
        this.menuBar = menuBar;
        this.glassPane = glassPane;
        this.contentPane = contentPane;
    }
    public void mouseMoved(MouseEvent e) {
        redispatchMouseEvent(e, false);
    }
    public void mouseDragged(MouseEvent e) {
        redispatchMouseEvent(e, false);
    }
    public void mouseClicked(MouseEvent e) {
        redispatchMouseEvent(e, false);
    }
    public void mouseEntered(MouseEvent e) {
        redispatchMouseEvent(e, false);
    }
    public void mouseExited(MouseEvent e) {
        redispatchMouseEvent(e, false);
    }
    public void mousePressed(MouseEvent e) {
        redispatchMouseEvent(e, false);
    }
    public void mouseReleased(MouseEvent e) {
        redispatchMouseEvent(e, true);
    }
    //A basic implementation of redispatching events.
    private void redispatchMouseEvent(MouseEvent e,
                                      boolean repaint) {
        Point glassPanePoint = e.getPoint();
        Container container = contentPane;
        Point containerPoint = SwingUtilities.convertPoint(
                                        glassPane,
                                        glassPanePoint,
                                        contentPane);
        if (containerPoint.y < 0) { //we're not in the content pane
            if (containerPoint.y + menuBar.getHeight() >= 0) {
                //The mouse event is over the menu bar.
                //Could handle specially.
            } else {
                //The mouse event is over non-system window
                //decorations, such as the ones provided by
                //the Java look and feel.
                //Could handle specially.
            }
        } else {
            //The mouse event is probably over the content pane.
            //Find out exactly which component it's over. 
            Component component =
                SwingUtilities.getDeepestComponentAt(
                                        container,
                                        containerPoint.x,
                                        containerPoint.y);
                            
            if ((component != null)
                && (component.equals(liveButton))) {
                //Forward events over the check box.
                Point componentPoint = SwingUtilities.convertPoint(
                                            glassPane,
                                            glassPanePoint,
                                            component);
                component.dispatchEvent(new MouseEvent(component,
                                                     e.getID(),
                                                     e.getWhen(),
                                                     e.getModifiers(),
                                                     componentPoint.x,
                                                     componentPoint.y,
                                                     e.getClickCount(),
                                                     e.isPopupTrigger()));
            }
        }
        
        //Update the glass pane if requested.
        if (repaint) {
            glassPane.setPoint(glassPanePoint);
            glassPane.repaint();
        }
    }
}
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