class="MsoNormal">弹球游戏分步解析（三）——滑块动起来
看过弹球游戏分步解析（一）、弹球游戏分步解析（二）的朋友应该知道，弹球游戏做到这一步可以实现小球在界面上“飞”了，不过既然是游戏，就要让玩家跟程序互动，没有互动就不能称之为游戏。
接下来我们就给我们的一个游戏添加一个滑块，用鼠标控制滑块横向移动，让滑块碰撞小球使其弹回。
做到控制滑块横向移动就需要使用鼠标监听器——MouseMotionListener来记录鼠标坐标，根据鼠标坐标位置来绘出滑块，移动时，部分朋友使用repant()的方法来删除原位置的滑块，可是这样做的结果是，滑块一直在闪，接下来我会介绍另一种方法来绘制滑块，这样滑块在移动的过程中就不会闪了；
和小球一样，先要建一个滑块类：
文件名：BandThread
package jumpingBall;
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import java.awt.Graphics;
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import javax.swing.JPanel;
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publicclass BandThread extends Thread {
??? privateint? length;
??? privateint? width;
??? privateintx;
??? privateinty;
??? privateintxlast;
??? privateintylast;
???
??? private JPanel jp;
??? private Graphics g;
??? public BandThread(JPanel jp,int x,int y){
??? ??? this.jp = jp;
??? ??? g =jp.getGraphics();
??? ??? this.x = x;
??? ??? this.y = y;
??? }
??? publicvoid run(){
??? ??? this.drawBand();
??? ??? this.clearBand();
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??? }
??? publicvoid drawBand(){
??? ???
??? ??? g.fillRect(x, 500, 100, 10);
??? }
??? publicvoid clearBand(){
??? ??? if(xlast!= x){
??? ??? g.setColor(jp.getBackground());
??? ??? g.fillRect(0, 500, x, 10);
??? ??? g.fillRect(x+100, 500,jp.getWidth()-x-100,10 );
??? ??? }
??? }
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}
加监听器：
文件名：bandListener
package jumpingBall;
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import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
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import javax.swing.JPanel;
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public class banLlistener implements MouseMotionListener {
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????????
???????? private? int x;
???????? private? int y;
???????? private JPanel jp;
???????? private Graphics g;
???????? public banLlistener(JPanel jp){
?????????????????? this.jp = jp;
?????????????????? this.g = jp.getGraphics();
???????? }
???????? @Override
???????? public void mouseDragged(MouseEvent e) {
?????????????????? // TODO Auto-generated method stub
??????????????????
???????? }
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???????? @Override
???????? public void mouseMoved(MouseEvent e) {
?????????????????? // TODO Auto-generated method stub
?????????????????? x = e.getX();
?????????????????? y = e.getY();
?????????????????? Date.xband = x;
?????????????????? Date.yband = y;
?????????????????? BandThread band = new BandThread(jp,x,y);
??????? band.start();
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??????????????????
??????????????????
???????? }
}
监听器所加位置：
文件名：BallThread
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package jumpingBall;
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import java.awt.Color;
import java.awt.Graphics;
import java.util.List;
import java.util.Random;
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import javax.swing.JPanel;
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public class BallThread extends Thread {
private static final int North = 1;//用四个整形的数据代表四个方向
private static final int West = 2;
private static final int South = 3;
private static final int East = 4;
private int Xdirection = West;//记录小球在X轴上的方向
private int Ydirection = North;//记录小球在y轴上的方向
private int radios;//半径
private Color color;//颜色
private int Xspeed;//x方向速度
private int Yspeed;//y方向速度
private int X;//当前位置x
private int Y;//当前位置y
private int LastX;//最后位置x
private int LastY;//最后位置y
private int xband;
private int yband;
private JPanel jp;//面板
private Graphics g;//画布
private boolean pauseFlag = false;//暂停标志（默认值否）
private boolean stopFlag = false;//停止标志（false——表示存在）
private boolean beread = false;//是否被储存在文件里过（默认值否）
?????? public BallThread(JPanel jp){
??? ??? ???this.jp = jp;
??? ??? ???this.g = jp.getGraphics();
?????? }
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?????? public void run(){
??? ??? ???banLlistener band =new banLlistener(jp);//定义滑块
??? ??? ???jp.addMouseMotionListener(band);//给滑块加入鼠标监听器
??? ??? ???if(beread==false){//如果没有被储存在文件里过
??? ??? ???this.setprivate();//方法作用：随机生成它的部分属性
??? ??? ???}
??? ??? ???while(true){//永真表示球会一直运动
??????? ??? ???
??? ?????? ???try{
??? ?????????? ???sleep(30);
??? ?????? ???}catch(InterruptedException e){
??? ?????????? ???e.printStackTrace();
??? ?????? ???}
??? ?????? ???if(stopFlag==true){//如果停止标示为true，停止该线程
??? ?????????? ???clearBall();
??? ?????????? ???return;
??? ?????? ???}
??? ?????? ???if(pauseFlag==true){//如果暂停标示为真，跳过之后的步骤进入下次循环
??? ?????????? ???continue;
??? ?????? ???}
??? ?????? ???
??? ?????? ???this.clearBall();//清除原来位置的小球
??? ?????? ???this.move();//小球运动
??? ?????? ???this.drawBall();//在新的位置画出小球
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??? ?????? ???
??? ??? ???}
??? ??? ?????? ???
}
?????? public void clearBall(){//清除小球
??? ??? ???Color color = jp.getBackground();//
??? ??? ???g.setColor(color);//
??? ??? ???g.fillOval(X, Y, radios*2, radios*2);//用背景色,填充之前小球的印记
?????? }
?????? public void drawBall(){
??? ??? ???g.setColor(color);//
??? ??? ???g.fillOval(X, Y, radios*2, radios*2);
?????? }
?????? public void setprivate(){//设置小球属性
??? ??? ???Random random = new Random();//随机
??? ??? ????radios = 10+random.nextInt(10);//半径
??? ??? ????color =new Color(random.nextInt(255),random.nextInt(255),random.nextInt(255));//颜色
??? ??? ????Xspeed = 2 + random.nextInt(10);//x方向速度
??? ??? ????Yspeed = 2+random.nextInt(10);//y方向速度
?????? }
?????? public void exit(boolean flag){//设置停止标示
??? ??? ???stopFlag = flag;
?????? }
?????? public void setpause(boolean flag){//设置暂停标示
??? ??? ???pauseFlag = flag;
?????? }
?????? public void move(){
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??? ??? ???switch(Xdirection){//对于x方向
??? ??? ???case 2:X = X - Xspeed;break;//如果小球的运动方向向西，X值减小
??? ??? ???case 4:X = X + Xspeed;break;//如果小球的运动方向向东，X值增大
??? ??? ???}
??? ??? ???switch(Ydirection){//对于y方向
??? ??? ???case 1:Y = Y - Yspeed;break;//如果小球的运动方向向北，Y值减小
??? ??? ???case 3:Y = Y + Yspeed;break;//如果小球的运动方向向难，Y值增大
??? ??? ???}
??? ??? ???//如果碰到边界，方向改变
??? ??? ???if(X<0+radios*2){
??? ?????? ???Xdirection = 4;
??? ??? ???}
??? ??? ???if(X>jp.getWidth()-radios*2){
??? ?????? ???Xdirection = 2;
??? ??? ???}
??? ??? ???if(Y<0+radios*2){
??? ?????? ???Ydirection = 3;
??? ??? ???}
??? ??? ???//如果掉到下面，该小球线程结束
??? ??? ???if(Y>jp.getHeight()-radios*2){
??? ?????? ???//Ydirection = 1;
??? ?????? ???BallThread ball = new BallThread(jp);
??? ?????? ???this.exit(true);
??? ?????? ???for(int i = 0;i<Date.allBall.size();i++){
??? ?????????? ??ball=Date.allBall.get(i);
??? ?????????? ??if(X == ball.X&&Y == ball.Y){
??? ????????????? ??Date.allBall.remove(i);
??? ?????????? ??}
??? ?????? ???}
??? ??? ???}
?? ???? ???//如果碰到滑块，弹回
??? ??? ???if(Y<500+radios/2&&Y>490-radios*2&&X>=Date.xband&&X<=(Date.xband+100)){
??? ?????? ???Ydirection = 1;
??? ??? ???}
?????? }
……………………………………
??? （之后的代码见弹球游戏分步解析（二））
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