java中如何自定义消息？

发信人: TOMHZT (snail), 信区: JavaTutorial
标  题: Re: java中如何自定义消息？
发信站: BBS 水木清华站 (Mon Nov  8 19:18:46 2004), 站内

这是从书上找的一个例子：
import java.util.EventObject;
import java.awt.Image;
class SignatureEvent extends EventObject
{
        protected Image signatureImage;
        
        public SignatureEvent(Object source, Image signature)
        {
                super(source);
                signatureImage = signature;
        }
        
        public Image getImage()
        {
                return signatureImage;
        }
}public interface SignatureEventListener
{
        public void userSigned(SignatureEvent signature);
        
}
import java.awt.Canvas;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
class SigningSurface extends Canvas
{
        protected int width, height;
        protected int x, y, lastX, lastY;
        protected Image offscreenImage = null;
        protected Graphics offscreenG;
        
        public SigningSurface()
        {
                enableEvents(AWTEvent.MOUSE_EVENT_MASK |
                             AWTEvent.MOUSE_MOTION_EVENT_MASK);
        }
        
        public void update(Graphics g)
        {
                paint(g);
        }
        
        public void paint(Graphics g)
        {
                if (offscreenImage == null)
                {
                        width  = getSize().width;
                        height = getSize().height;
                        offscreenImage = createImage(width, height);
                        if (offscreenImage == null)
                        {
                                System.out.println("Error: Couldn't create offScreen.");
                        }
                        offscreenG = offscreenImage.getGraphics();
                }
                g.drawImage(offscreenImage, 0, 0, this);
        }
        
        public void processMouseEvent(MouseEvent mouseEvent)
        {
                x = mouseEvent.getX();
                y = mouseEvent.getY();
                
                switch (mouseEvent.getID())
                {
                        case MouseEvent.MOUSE_PRESSED :
                        {
                                lastX = x;
                                lastY = y;
                                repaint();
                                break;
                        }
                        default:
                            break;
                }
        }
        
        protected void processMouseMotionEvent(MouseEvent mouseMotionEvent)
        {
                x = mouseMotionEvent.getX();
                y = mouseMotionEvent.getY();
                
                switch (mouseMotionEvent.getID())
                {
                        case MouseEvent.MOUSE_DRAGGED:
                        {
                                offscreenG.drawLine(x, y, lastX, lastY);
                                lastX = x;
                                lastY = y;
                                repaint();
                                break;
                        }
                        default:
                            break;
                }
        }
        
        public Image getImage()
        {
                return offscreenImage;
        }
        
        public void wipeSignature()
        {
                wipeImage(offscreenImage, Color.white, this);
                offscreenG.setColor(Color.black);
                repaint();
        }
        
        public static void wipeImage(Image im, Color col, ImageObserver observer)
        {
                Graphics g;
                int width, height;
                
                g = im.getGraphics();
                width  = im.getWidth(observer);
                height = im.getHeight(observer);
                g.setColor(col);
                g.fillRect(0, 0, width, height);
        }
        
} //endof class SigningSurface

import java.awt.*;
import java.awt.event.*;
import java.util.*;
public class SignMe extends Panel implements ActionListener
{
        protected SigningSurface scribble;
        protected Button eraseButton, acceptButton;
        protected SignatureEventListener sigListener = null;
        
        public SignMe()
        {
                Panel buttonsPanel, but1Panel, but2Panel;
                setLayout(new BorderLayout());
                scribble = new SigningSurface();
                buttonsPanel = new Panel();
                but1Panel = new Panel();
                but2Panel = new Panel();
                
                eraseButton = new Button("擦除");
                acceptButton = new Button("确定");
                
                but1Panel.add(eraseButton);
                but2Panel.add(acceptButton);
                buttonsPanel.add(but1Panel);
                buttonsPanel.add(but2Panel);
                add(scribble, "Center");
                add(buttonsPanel, "South");
                
                eraseButton.addActionListener(this);
                acceptButton.addActionListener(this);
        }
        
        public void actionPerformed(ActionEvent buttonClick)
        {
                if (buttonClick.getSource() == eraseButton)
                {
                        scribble.wipeSignature();
                }
                if (buttonClick.getSource() == acceptButton)
                {
                        System.out.println("user accepted signature!");
                        fireSignedEvent();
                }
        }
        
        public void addSignatureListener(SignatureEventListener listener)
                    throws java.util.TooManyListenersException
        {
                if (sigListener != null)
                {
                        throw new TooManyListenersException("SignMe already has an event listener");
                }
                sigListener = listener;
        }
        
        public void removeSignatureListener(SignatureEventListener listener)
        {
                if (sigListener == null)
                {
                        throw new IllegalArgumentException("Can't remove SignMe event");
                }
                
                if (sigListener != listener)
                {
                        throw new IllegalArgumentException("different from currently set!");
                }
                sigListener = null;
        }
        
        protected void fireSignedEvent()
        {
                SignatureEvent event;
                
                if (sigListener != null)
                {
                        event = new SignatureEvent(this, scribble.getImage());
                        sigListener.userSigned(event);
                }
        }
} //end of class SignMe

import java.awt.Frame;
import utilities.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
class SignMeClient extends Frame implements SignatureEventListener
{
        protected SignMe sigWindow;
        
        public static void main(String[] args)
        {
                new SignMeClient();
        }
        
        public SignMeClient()
        {
                super("Sign Me Demo Window");
                sigWindow = new SignMe();
                
                try
                {
                        sigWindow.addSignatureListener(this);
                }
                catch (TooManyListenersException ex)
                {
                        System.out.println("Could not register " + ex);
                }
                
                add(sigWindow, "Center");
                setSize(new Dimension(350, 250));
                setVisible(true);
        }
        
        public void userSigned(SignatureEvent signed)
        {
                Frame receivedSignWindow;
                Graphics g;
                Image sigImage;
                int width, height;
                
                receivedSignWindow = new Frame("Received Signature");
                sigImage = signed.getImage();
                width = sigImage.getWidth(this);
                height = sigImage.getHeight(this);
                receivedSignWindow.setSize(new Dimension(width + 20, height + 20));
                receivedSignWindow.setVisible(true);
                MiscKit.delay(300);
                
                g = receivedSignWindow.getGraphics();
                int x = receivedSignWindow.getInsets().left;
                int y = receivedSignWindow.getInsets().top;
                g.drawImage(sigImage, x, y, receivedSignWindow);
                MiscKit.delay(1000);
                receivedSignWindow.setVisible(false);
        }
        
}


【 在 liyuexp (雁南飞) 的大作中提到: 】
: 如何在java中自定义消息 并且接受处理 请给个例子


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