tumbleweed.java

用Java/C#开发手机程序及移动应用光盘代码。J2ME核心类及MIDlet类；基于Java开发MIDlet程序；图形处理及低级事件处理；多线程编程；即时消息传送；I/O及网络编程；数据库编程；多媒体

import java.util.Random;
import javax.microedition.lcdui.*;
import javax.microedition.lcdui.game.*;

public class Tumbleweed extends Sprite {

	static int WIDTH = 16;
	Random myRandom = new Random();

	boolean myJumpedOver; // 是否被跳过
	boolean myLeft; // 是否是从左边而来

	int myY; // 纵向位置

	/**
	 * 构造方法
	 */
	public Tumbleweed(boolean left) throws Exception {
		super(Image.createImage("/icons/tumbleweed.png"), 
		WIDTH, WIDTH);
		myY = JumpManager.DISP_HEIGHT - WIDTH - 2;
		myLeft = left;
		if(!myLeft) {
			setTransform(TRANS_MIRROR);
		}
		myJumpedOver = false;
		setVisible(false);
	}

	/**
	 * 重置
	 */
	void reset() {
		setVisible(false);
		myJumpedOver = false;
	}

	/**
	 * 步进，改变其图片，并计算得分
	 */
	int advance(Cowboy cowboy, int tickCount, boolean left,
				int currentLeftBound, int currentRightBound) {
		int retVal = 0;
		// 已出界，被重置，以便重新使用
		if((getRefPixelX() + WIDTH <= currentLeftBound) || 
			 (getRefPixelX() - WIDTH >= currentRightBound)) {
			setVisible(false);
		} 
		if(!isVisible()) {
			int rand = getRandomInt(100);
			if(rand == 3) { // 以3％的机会被利用
				myJumpedOver = false;
				setVisible(true);
				if(myLeft) {
					setRefPixelPosition(currentRightBound, myY);
					move(-1, 0);
				} else {
					setRefPixelPosition(currentLeftBound, myY);
					move(1, 0);
				}
			}
		} else {
			if(tickCount % 2 == 0) { // slow the animation down a little
				nextFrame();
			}
			if(myLeft) {
				move(-3, 0);
				if((! myJumpedOver) && 
					 (getRefPixelX() < cowboy.getRefPixelX())) {
					myJumpedOver = true;
					retVal = cowboy.increaseScoreThisJump();
				}
			} else {
				move(3, 0);
				if((! myJumpedOver) && 
					 (getRefPixelX() > 
						cowboy.getRefPixelX() + Cowboy.WIDTH)) {
					myJumpedOver = true;
					retVal = cowboy.increaseScoreThisJump();
				}
			}
		}
		return(retVal);
	}

	/**
	 * 随机数 
	 */
	public int getRandomInt(int upper) {
		int retVal = myRandom.nextInt() % upper;
		if(retVal < 0) {
			retVal += upper;
		}
		return(retVal);
	}

}