java 游戏编程 (四)

通过前面的总结，动画已经可以很好的运行了，现在要让动画动起来，这里说的动起来就是能让它运动，不是原地的动画，而是坐标发生的变化。也就是可以再屏幕上独立运动的图形。我们用Fly命名它。
Fly有两个特性，就是位置和速度。位置就是它当前在屏幕中的坐标，速度就是它的速率和运动方向。现在定义Fly这个类

/**
 * 
 */
package com.jsheng.game.util;

import java.awt.Image;

/** 
 * company: jsheng
 * @author wanghn      [e-mail]
 */
public class Fly {
	private Animation animation;  //原来的动画
	
	//位置
	private float x;
	private float y;
	
	//速度
	private float dx;
	private float dy;
	
	public Fly(Animation anmi){
		this.animation = anmi;
	}
	
	//根据速度更新位置
	public void update(long passedTime){
		x+=dx*passedTime;
		y+=dy*passedTime;
		animation.update(passedTime);
	}

	public float getX() {
		return x;
	}

	public void setX(float x) {
		this.x = x;
	}

	public float getY() {
		return y;
	}

	public void setY(float y) {
		this.y = y;
	}

	public float getDx() {
		return dx;
	}

	public void setDx(float dx) {
		this.dx = dx;
	}

	public float getDy() {
		return dy;
	}

	public void setDy(float dy) {
		this.dy = dy;
	}
	
	public Image getImage(){
		return animation.getImage();
	}
	
	public int getWidth(){
		return animation.getImage().getWidth(null);
	}
	
	public int getHeight(){
		return animation.getImage().getHeight(null);
	}
}

下面让Fly在屏幕中动起来

package com.jsheng.game.test1;

import java.awt.DisplayMode;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import javax.swing.ImageIcon;
import com.jsheng.game.util.Animation;
import com.jsheng.game.util.Fly;
import com.jsheng.game.util.ScreenManager;


public class SpriteTest1 {

    public static void main(String args[]) {
        SpriteTest1 test = new SpriteTest1();
        test.run();
    }

    	//上节说到提供一个可选择的现实数组，让这个类自动选择合适的DisplayMode
    private static final DisplayMode POSSIBLE_MODES[] = {
        new DisplayMode(800, 600, 32, 0),
        new DisplayMode(800, 600, 24, 0),
        new DisplayMode(800, 600, 16, 0),
        new DisplayMode(640, 480, 32, 0),
        new DisplayMode(640, 480, 24, 0),
        new DisplayMode(640, 480, 16, 0)
    };

    private ScreenManager screen;
    private Image bgImage;
    private Fly fly;

    public void loadImages() {
        // 读取所有图片
        bgImage = loadImage("images/bg.jpg");
        Image player1 = loadImage("images/1.jpg");
        Image player2 = loadImage("images/2.jpg");
        Image player3 = loadImage("images/3.jpg");

        // 构造出动画
        Animation anim = new Animation();
        anim.addFrame(player1, 250);
        anim.addFrame(player2, 150);
        anim.addFrame(player1, 150);
        anim.addFrame(player2, 150);
        anim.addFrame(player3, 200);
        anim.addFrame(player2, 150);
        fly = new Fly(anim);

        // 设置起初Fly的速度
        fly.setDx(0.2f);
        fly.setDy(0.2f);  //这里设置了x和y,所以一开始是向右下飞.
    }

    private Image loadImage(String fileName) {
        return new ImageIcon(fileName).getImage();
    }

    public void run() {
        screen = new ScreenManager();
        try {
            DisplayMode displayMode =
                screen.findFirstCompatibleMode(POSSIBLE_MODES);
            screen.setFullScreen(displayMode);
            loadImages();
            animationLoop();
        }
        finally {
            screen.restoreScreen();
        }
    }

    public void animationLoop() {
        long startTime = System.currentTimeMillis();
        long currTime = startTime;

        while (currTime - startTime < 100000) {
            long elapsedTime =
                System.currentTimeMillis() - currTime;
            currTime += elapsedTime;
            update(elapsedTime);
            Graphics2D g = screen.getGraphics();
            draw(g);
            g.dispose();
            screen.update();

                try {
					Thread.sleep(20);
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}

        }
    }


    public void update(long elapsedTime) {
        // 判断是否飞到了屏幕边缘
        if (fly.getX() < 0) {
            fly.setDx(Math.abs(fly.getDx()));
        }
        else if (fly.getX() + fly.getWidth() >=
            screen.getWidth())
        {
            fly.setDx(-Math.abs(fly.getDx()));
        }
        if (fly.getY() < 0) {
            fly.setDy(Math.abs(fly.getDy()));
        }
        else if (fly.getY() + fly.getHeight() >=
            screen.getHeight())
        {
            fly.setDy(-Math.abs(fly.getDy()));
        }
        fly.update(elapsedTime);
    }

    //不停的去画，通过改变 Fly的xy值，也就是Fly的位置，来使Fly动起来
    public void draw(Graphics g) {
        g.drawImage(bgImage, 0, 0, null);
        g.drawImage(fly.getImage(),
            Math.round(fly.getX()),
            Math.round(fly.getY()),
            null);
    }

}