bulletsprite.java

来自「是一本开发J2ME程序的50个例题的源代码」· Java 代码 · 共 46 行

package demo;

import javax.microedition.lcdui.Image;
import javax.microedition.lcdui.game.Sprite;

public class BulletSprite extends  Sprite{
	private int m_nSpeed		= 0;		//子弹速率
	private boolean m_bRight	= true;		//子弹方向（true向右、false向右）
	
	public BulletSprite(Image image, int frameWidth, int frameHeight){
		super(image, frameWidth, frameHeight);
		defineReferencePixel( frameWidth / 2, frameHeight / 2 );
		setVisible(false);
	}
	//产生子弹
	//参数nX、nY分别是子弹位置的横纵坐标
	//参数bLeft指定子弹方向，参数nSpeed指定子弹速率
	public void Start( int nX, int nY, boolean bRight, int nSpeed ) {
		m_nSpeed 	= nSpeed;
		m_bRight	= bRight;
		setRefPixelPosition( nX, nY );
		setVisible(true);
	}
	public void Stop() {
		setVisible(false);
	}
	//逻辑操作控制子弹运动
	public void Logic(int scrWidth, int scrHeight) {
		if( !isVisible() )
			return;
		int nX = getRefPixelX();
		int nY = getRefPixelY();
		if( m_bRight ){
			nX += m_nSpeed;
			if( nX > scrWidth )
				setVisible(false);
		}
		else{
			nX -= m_nSpeed;
			if( nX < 0 )
				setVisible(false);
		}
		setRefPixelPosition( nX, nY );		
	}
}