J2ME中定点库MathFP使用入门

import javax.microedition.lcdui.Canvas;

import javax.microedition.lcdui.Graphics;

import net.jscience.util.MathFP;

/**

 * 小数运算演示Canvas

 * @author Jagie

 *

 */

public class FloatCanvas

extends Canvas implements Runnable

{

    //用于统计屏幕刷新次数

    int paintCount;

    //屏幕宽度，高度。定点数

    int w_FP, h_FP;

    //当前点坐标，前一点坐标,定点数

    int curX_FP, curY_FP,

lastX_FP, lastY_FP;

    //速率

    public static final int RATE = 5;

    public FloatCanvas()

{

        w_FP = MathFP.toFP(this.getWidth());

        h_FP = MathFP.toFP(this.getHeight());

        //开始点处于屏幕的左下角

        lastX_FP = MathFP.toFP(0);

        lastY_FP = h_FP;

        new Thread(this).start();

    }

    protected void paint(Graphics g)

{

        //第一次只是清屏

        if (paintCount == 0)

{

            g.setColor(0);

            g.fillRect(0, 0, w_FP, h_FP);

        }

else

{

            //画线

            g.setColor(0x00ff00);

            //把定点数转换成整数

            g.drawLine(MathFP.toInt(lastX_FP),

MathFP.toInt(lastY_FP), MathFP

   .toInt(curX_FP), MathFP.toInt(curY_FP));

        }

            

            paintCount++;

        

    }

    public void run()

{

        //当前点没有超出屏幕时循环

        while (curX_FP <= w_FP &&

curY_FP <= h_FP

&& MathFP.toInt(curX_FP) >= 0

                && MathFP.toInt(curY_FP)

>= 0) {

            //60度角度转换成弧度

            int radians =

MathFP.div(MathFP.mul(MathFP.toFP(60),

MathFP.PI),

                    MathFP.toFP(180));

            //x方向增量

            int deltaX = MathFP.mul(MathFP.toFP(RATE),

MathFP.cos(radians));

            //y方向增量

            int deltaY = MathFP.mul(MathFP.toFP(RATE),

MathFP.sin(radians));

            //新坐标，定点数

            curX_FP = lastX_FP + deltaX;

            curY_FP = lastY_FP - deltaY;

            System.out.println(curX_FP + "," + curY_FP);

            repaint();

            try {

                Thread.sleep(100);

            } catch (InterruptedException e) {

                // TODO Auto-generated catch block

                e.printStackTrace();

            }

            //新坐标成为旧坐标

            lastX_FP = curX_FP;

            lastY_FP = curY_FP;

        }

    }

}