imager.java

《java设计模式》一书的源码

import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.text.*;
import javax.swing.border.*;
import javax.accessibility.*;

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.io.*;

public class Imager extends JPanel implements Chain {
    private Chain nextChain;
    private Image img;
    private boolean loaded;

    public Imager() {
        super();            
        loaded = false;
        setBorder(new BevelBorder(BevelBorder.RAISED));
    }
//------------------------------------------
    public void addChain(Chain c) {
        nextChain = c;    //next in chain of resp
    }
//------------------------------------------
    public void sendToChain(String mesg) {
        //if there is a JPEG file with this root name
        //load it and display it.
        if (findImage(mesg))
            loadImage(mesg+".jpg");
        else
            //Otherwise, pass request along chain
            nextChain.sendToChain(mesg);
    }
//------------------------------------------
    public Chain getChain() {
        return nextChain;
    }          
//------------------------------------------
    public void paint(Graphics g) {
        if (loaded) {
            g.drawImage(img, 0, 0, this);
        }
    }
//------------------------------------------
    private void loadImage(String file) {
        loaded = false;
        MediaTracker tracker = new MediaTracker(this);
        img = Toolkit.getDefaultToolkit().getImage(file);
        tracker.addImage(img, 0);     //watch for image loading

        //this begins actual image loading
        try {
            tracker.waitForID(0,1);
        } catch (InterruptedException e) {
        }
        loaded = true;
        validate();
        repaint();
    }
//------------------------------------------
    private boolean findImage(String file) {
        XFile xfile = null;

        File dir = new File(System.getProperty("user.dir"));
        boolean found = false;
        String files[] = dir.list();
        int i = 0; 
        while ((! found) && (i < files.length)) {
            xfile = new XFile(files[i]);
            found = xfile.matchRoot(file);
            if (!found)
                i++;
        }
        if (found) {
            return xfile.matchName(file+".jpg");
        } else
            return found;     //false
    }
}