imageproxy.java

来自「源码为科学出版社出版的英文<java设计模式>(影印版)所用的所有例」· Java 代码 · 共 70 行

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

import java.awt.*; 

public class ImageProxy extends JPanel
implements Runnable {
    private int height, width;
    private MediaTracker tracker;
    private Image img;
    private JFrame frame;
    private Thread imageCheck;  //to monitor loading
//----------------------------------
    public ImageProxy(String filename, int w, int h) {
        height = h;
        width = w;

        tracker = new MediaTracker(this);
        img = Toolkit.getDefaultToolkit().getImage(filename);
        tracker.addImage(img, 0);     //watch for image loading

        imageCheck = new Thread(this);
        imageCheck.start();           //start 2nd thread monitor

        //this begins actual image loading
        try {
            tracker.waitForID(0,1);
        } catch (InterruptedException e) {
        }
    }
//------------------------------------
    public void paint(Graphics g) {
        if (tracker.checkID(0)) {
            height = img.getHeight(frame);   //get height
            width = img.getWidth(frame);     //and width

            g.setColor(Color.lightGray);     //erase box
            g.fillRect(0,0, width, height);
            g.drawImage(img, 0, 0, this);   //draw loaded image
        } else {
            //draw box outlining image if not loaded yet
            g.setColor(Color.black);
            g.drawRect(1, 1, width-2, height-2);
        }
    }
    //------------------------------------
    public Dimension getPreferredSize() {
        return new Dimension(width, height);
    }
    //public int getWidth() {return width;}
    //public int getHeight(){return height;}
    //------------------------------------
    public void run() {
        /**this thread monitors image loading
        and repaints when done
        the 1000 msec is artifically long
        to allow demo to display with delay*/
        try {
            Thread.sleep(1000);
            while (! tracker.checkID(0))
                Thread.sleep(1000);
        } catch (Exception e) {
        }
        repaint();
    }
}