scrollimagecanvas.java

《精通JAVA手机游戏与应用程序设计》随书光盘

package ScrollImage;

import java.io.IOException;

import javax.microedition.lcdui.Canvas;
import javax.microedition.lcdui.Graphics;
import javax.microedition.lcdui.Image;

class ScrollImageCanvas extends Canvas implements Runnable {
	Image pic;

	int drawX, drawY; //原点座标

	int scrollleft;//左右移动最大距离

	boolean isleft = true; //是否往左移动

	ScrollImageCanvas() {
		try {
			//装入png图片文件
			pic = Image.createImage("/ScrollPic.png");
		} catch (IOException e) {
			//需要import java.io.*;
			System.out.println("load png resource error " + e.getMessage());
			pic = null;
		}

		scrollleft = this.getWidth() - pic.getWidth();
		

		drawX = 0;//getWidth();
		drawY = getHeight();
	}

	protected void paint(Graphics g) {

		g.translate(drawX, 0);
		g.drawImage(pic, 0, drawY, Graphics.BOTTOM | Graphics.LEFT);

	}

	public void run() {

		while (true) {
			this.scroll();
			repaint();
			try {
				Thread.sleep(50);
			} catch (InterruptedException e) {
				System.out.println("sleep error : " + e.getMessage());
			}
		}

	}

	public void start() {
		Thread t = new Thread(this);
		t.start();
	}
	//滚动屏幕
	protected void scroll() {
		if (isleft) {
			//如果往左滚动完整个图片则往右滚动
			if (drawX >= scrollleft)
				drawX = drawX - 1;
			else {
				isleft = false;
			}
		} else {
			if (drawX <= 0)
				drawX = drawX + 1;
			else {
				isleft = true;
			}
		}
	}
}