imagescrolltest.java

java手机程序开发随书光盘源代码

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import java.util.*;

public class ImageScrollTest extends MIDlet{

	Display display;
	MyCanvas myCanvas;

	public ImageScrollTest(){
		display = Display.getDisplay(this);
		myCanvas = new MyCanvas();
	}

	public void startApp(){
		display.setCurrent(myCanvas);
	}

	public void pauseApp(){
	}

	public void destroyApp(boolean unconditional){
	}

	class MyCanvas extends Canvas implements CommandListener{

		Command exitCmd;
		Image offScreen;
		Image spriteImage;
		Image background;
		int x, y;
		int imageX, imageY;
		int imageWidth, imageHeight;

		public MyCanvas(){

			if(!isDoubleBuffered()){
				offScreen = Image.createImage(getWidth(), getHeight());
			}

			try{
				spriteImage = Image.createImage("/sprite.png");
				background = Image.createImage("/background.png");
			}
			catch(Exception ex){}

			imageWidth = background.getWidth();
			imageHeight = background.getHeight();

			exitCmd = new Command("退出", Command.EXIT, 1);
			addCommand(exitCmd);
			setCommandListener(this);
		}

		public void paint(Graphics g){

			Graphics old = g;

			if(offScreen != null){
				g = offScreen.getGraphics();
			}

			g.setColor(0xFFFFFF);
			g.fillRect(0, 0, getWidth(), getHeight());


			g.drawImage(background, imageX, imageY, Graphics.LEFT|Graphics.TOP);
			g.drawImage(background, imageX, imageY-imageHeight, Graphics.LEFT|Graphics.TOP);

			g.drawImage(background, imageX-imageWidth, imageY, Graphics.LEFT|Graphics.TOP);
			g.drawImage(background, imageX-imageWidth, imageY-imageHeight, Graphics.LEFT|Graphics.TOP);


			g.drawImage(spriteImage,
						(getWidth()-spriteImage.getWidth())/2,
						(getHeight()-spriteImage.getHeight())/2,
						Graphics.LEFT|Graphics.TOP);

			g.setColor(0);
			g.drawString("当前位置："+x+","+y,
						 10,
						 getHeight() - 20,
						 Graphics.LEFT|Graphics.TOP);

			if(g != old){
				old.drawImage(offScreen, 0, 0, Graphics.LEFT|Graphics.TOP);
			}
		}

		public void keyPressed(int keyCode){
			int gameAction = getGameAction(keyCode);
			switch(gameAction){
			case Canvas.UP:
				y-=5;
				imageY+=5;
				if(imageY>=getHeight()) imageY -= getHeight();
				repaint();
			break;
			case Canvas.DOWN:
				y+=5;
				imageY-=5;
				if(imageY<=0) imageY += getHeight();
				repaint();
			break;
			case Canvas.LEFT:
				x-=5;
				imageX+=5;
				if(imageX>=getWidth()) imageX -= getWidth();
				repaint();
			break;
			case Canvas.RIGHT:
				x+=5;
				imageX-=5;
				if(imageX<=0) imageX += getWidth();
				repaint();
			break;
			}
		}

		public void keyReleased(int keyCode){
		}

		public void keyRepeated(int keyCode){
		}

		public void commandAction(Command c, Displayable d){

			if(c == exitCmd){
				destroyApp(true);
				notifyDestroyed();
			}
		}
	}
}