bouncingball.java

来自「Bounce ball on mobile phone J2ME Happy」· Java 代码 · 共 55 行

/*
 * BouncingBall.java
 * Andreas Jakl
 */

package Bounce;

import javax.microedition.lcdui.Graphics;

public class BouncingBall
{
    private int maxWidth;
    private int maxHeight;
    private int xPos;
    private int yPos;
    private int xDir;
    private int yDir;
    private int radius;
    
    /** Creates a new instance of BouncingBall */
    public BouncingBall ()
    {
    }
    
    public void init (final int aMaxWidth, final int aMaxHeight)
    {
	maxWidth = aMaxWidth;
	maxHeight = aMaxHeight;
	xPos = maxWidth / 2;
	yPos = maxHeight / 2;
	radius = 20;
	xDir = 3;
	yDir = 3;
    }
    
    public void paint (Graphics g)
    {
	g.setColor (255, 0, 0);
	g.fillArc (xPos, yPos, radius, radius, 0, 360);
    }
    
    public void updatePosition()
    {
	xPos += xDir;
	yPos += yDir;
	
	if (xPos + radius >= maxWidth || xPos <= 0)
	    xDir = -xDir;
	    
	if (yPos + radius >= maxHeight || yPos <= 0)
	    yDir = -yDir;
    }
    
}