Java JFrame架构中RootPane--GlassPane的应用

Java JFrame中从里到外由frame-layeredPane-contentPane-menuBar(optional)-glassPane构成。layered pane用处很大就不必说了。现在是其中glass pane的应用。

package com.han;

import java.awt.Color;
import java.awt.Component;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.awt.event.MouseEvent;

import javax.swing.AbstractButton;
import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.SwingUtilities;
import javax.swing.event.MouseInputListener;

/**
 * It contains a check box that lets you set whether the glass pane is "visible"
 * — whether it can get events and paint itself onscreen. When the glass pane is
 * visible, it blocks all input events from reaching the components in the
 * content pane. It also paints a red dot in the place where it last detected a
 * mouse-pressed event.
 * 
 * @author HAN
 * 
 */
public class GlassPane_1 {

	/**
	 * Create and show GUI. 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("GlassPane Demo 1");
		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 both above the menu bar and the
		// content pane, and is an item listener on the changeButton.
		MyGlassPane myGlassPane = new MyGlassPane(contentPane, changeButton);
		changeButton.addItemListener(myGlassPane);
		frame.setGlassPane(myGlassPane);

		// Show the window.
		frame.pack();
		frame.setVisible(true);

	}

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		// Schedule a job for the event-dispatching thread:
		// creating and showing its application's GUI.
		SwingUtilities.invokeLater(new Runnable() {

			@Override
			public void run() {
				// TODO Auto-generated method stub
				createAndShowGUI();

			}

		});
	}
}

/**
 * We have to provide our own glass pane so that it can paint itself.
 * 
 * @author HAN
 * 
 */
@SuppressWarnings("serial")
class MyGlassPane extends JComponent implements ItemListener {
	private Point point;

	// React to changeButton click.
	@Override
	public void itemStateChanged(ItemEvent e) {
		// TODO Auto-generated method stub
		setVisible(e.getStateChange() == ItemEvent.SELECTED);
	}

	@Override
	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 point) {
		this.point = point;
	}

	MyGlassPane(Container contentPane, AbstractButton changeButton) {
		// Should forward the input events to check box.
		CBListener listener = new CBListener(contentPane, changeButton, this);
		addMouseListener(listener);
		addMouseMotionListener(listener);
	}
}

/**
 * Listen for all events that our check box is likely to be interested in.
 * Redispatch them to the check box.
 * 
 * @author HAN
 * 
 */
class CBListener implements MouseInputListener {
	private Container contentPane;
	private Component changeButton;
	private MyGlassPane glassPane;

	CBListener(Container contentPane, Component changeButton,
			MyGlassPane glassPane) {
		this.contentPane = contentPane;
		this.changeButton = changeButton;
		this.glassPane = glassPane;
	}

	@Override
	public void mouseClicked(MouseEvent e) {
		// TODO Auto-generated method stub
		redispatchMouseEvent(e, false);
	}

	@Override
	public void mousePressed(MouseEvent e) {
		// TODO Auto-generated method stub
		redispatchMouseEvent(e, true);
	}

	@Override
	public void mouseReleased(MouseEvent e) {
		// TODO Auto-generated method stub
		redispatchMouseEvent(e, false);
	}

	@Override
	public void mouseEntered(MouseEvent e) {
		// TODO Auto-generated method stub
		redispatchMouseEvent(e, false);
	}

	@Override
	public void mouseExited(MouseEvent e) {
		// TODO Auto-generated method stub
		redispatchMouseEvent(e, false);
	}

	@Override
	public void mouseDragged(MouseEvent e) {
		// TODO Auto-generated method stub
		redispatchMouseEvent(e, false);
	}

	@Override
	public void mouseMoved(MouseEvent e) {
		// TODO Auto-generated method stub
		redispatchMouseEvent(e, false);
	}

	// A basic implementation of redispatching events.
	private void redispatchMouseEvent(MouseEvent e, Boolean repaint) {
		Point glassPanePoint = e.getPoint();
		Point contentPanePoint = SwingUtilities.convertPoint(glassPane,
				glassPanePoint, contentPane);
		Component component = SwingUtilities.getDeepestComponentAt(contentPane,
				contentPanePoint.x, contentPanePoint.y);
		if (component != null && component.equals(changeButton)) {
			Point componentPoint = SwingUtilities.convertPoint(glassPane,
					glassPanePoint, component);
			changeButton.dispatchEvent(new MouseEvent(component, e.getID(), e
					.getWhen(), e.getModifiers(), componentPoint.x,
					componentPoint.y, e.getClickCount(), e.isPopupTrigger()));
		} else {
			if (repaint) {
				glassPane.setPoint(glassPanePoint);
				glassPane.repaint();
			}
		}
	}
}

It contains a check box that lets you set whether the glass pane is "visible" — whether it can get events and paint itself onscreen. When the glass pane is visible, it blocks all input events from reaching the components in the content pane. It also paints a red dot in the place where it last detected a mouse-pressed event.