imagemidlet.java

<j2me 开发精解> 詹建光著 里所有的源码。对J2me的开发相当有帮助

package com.j2medev.chapter3.image;

import java.io.IOException;
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

public class ImageMidlet extends MIDlet implements CommandListener{
    
    private Image img = null;
    private Display display = null;
    private List main = new List("Image",List.IMPLICIT);
    private Command exitCommand = new Command("Exit",Command.EXIT,1);
    private Command backCommand = new Command("back",Command.BACK, 2);
    
    public ImageMidlet(){
        if(display == null){
            display = Display.getDisplay(this);
            try{
                img = Image.createImage("/baby.png");
            }catch(IOException ex){
                ex.printStackTrace();
            }
            //创建缩略图
            main.append("Lovely Baby",createThumbnail(img, 40));
            main.addCommand(exitCommand);
            main.setCommandListener(this);
        }
    }
    public void startApp() {
        display.setCurrent(main);
    }
    
    public void pauseApp() {
    }
    
    public void destroyApp(boolean unconditional) {
    }
    //借助Clipping的概念实现图片缩放，精度有限
    private Image createThumbnail(Image image,int width) {
        int sourceWidth = image.getWidth();
        int sourceHeight = image.getHeight();
        
        int thumbWidth = width;
        int thumbHeight = -1;
        
        if (thumbHeight == -1)
            //计算小图片高度
            thumbHeight = thumbWidth * sourceHeight / sourceWidth;
        //创建缩略图
        Image thumb = Image.createImage(thumbWidth, thumbHeight);
        Graphics g = thumb.getGraphics();
        
        for (int y = 0; y < thumbHeight; y++) {
            for (int x = 0; x < thumbWidth; x++) {
                g.setClip(x, y, 1, 1);
                int dx = x * sourceWidth / thumbWidth;
                int dy = y * sourceHeight / thumbHeight;
                g.drawImage(image, x - dx, y - dy, Graphics.LEFT | Graphics.TOP);
            }
        }
        Image immutableThumb = Image.createImage(thumb);
        return immutableThumb;
    }
    
    public void commandAction(Command cmd,Displayable displayable){
        if(cmd == List.SELECT_COMMAND){
            //显示图片
            ImageCanvas canvas = new ImageCanvas(img);
            canvas.addCommand(backCommand);
            canvas.setCommandListener(this);
            display.setCurrent(canvas);
        }else if(cmd == backCommand){
            display.setCurrent(main);
        }else if(cmd == exitCommand){
            destroyApp(false);
            notifyDestroyed();
        }
    }
}