fish.java

诺基亚经典小程序。。。j2me—fishtank...(动态)

package fishtank;

import javax.microedition.lcdui.*;
import com.nokia.mid.ui.*;
import java.util.Random;


public class Fish
{
    // These NUM values depend on the images actually included
    // in the MIDLET JAR file.
    private static final int TYPE_NUM = 3;
    private static final int FRAME_NUM = 2;

    private static final Image[][] fishImage;
    private static final int fishWidth, fishHeight;
    private static final Random random = new Random();

    private final int type;

    private int frame;
    private int x, y, z;
    private int vx, vy;
    private int ticksSinceLastChangeX = 0;
    private int ticksSinceLastChangeY = 0;
    private int ticksSinceLastChangeD = 0;

    static
    {
        fishImage = new Image[TYPE_NUM][FRAME_NUM];

        int i = 0;
        int k = 0;
        try
        {
            for (i = 0; i < TYPE_NUM; i ++)
            {
                for (k = 0; k < FRAME_NUM; k ++)
                {
                    fishImage[i][k] =
                        Image.createImage("/res/fish" + i + k + ".png");
                }
            }
        }
        catch (java.io.IOException e)
        {
            fishImage[i][k] = null;
        }

        // This MIDlet implicitly assumes that all the Images
        // are the same width and height.

        fishWidth  = fishImage[0][0].getWidth();
        fishHeight = fishImage[0][0].getHeight();
    }


    public Fish()
    {
        type = rand(TYPE_NUM);
        frame = rand(FRAME_NUM);

        x = rand(FishTankCanvas.waterWidth - fishWidth);
        y = rand(FishTankCanvas.waterHeight - fishHeight);

        vx = rand(2) * 2 - 1;    // -1 or 1
        vy = rand(3) - 1;        // -1, 0 or 1

        z = rand(FishTankCanvas.NUM_PLANES);
    }


    public void tick()
    {
        ticksSinceLastChangeX++;
        ticksSinceLastChangeY++;
        ticksSinceLastChangeD++;

        // mostly continue as we are, but sometimes randomly change
        if ((ticksSinceLastChangeX > 20) && (rand(20) == 0))
        {
            vx = rand(2) * 2 - 1; // -1 or 1
            ticksSinceLastChangeX = 0;
        }

        // if moving would take us off the left or right of the water,
        // reverse
        if (((vx < 0) && (x + vx < 0)) ||
            ((vx > 0) && (x + fishWidth + vx > FishTankCanvas.waterWidth)))
        {
            vx = -vx;
            ticksSinceLastChangeX = 0;
        }

        // mostly continue as we are, but sometimes randomly change
        if ((ticksSinceLastChangeY > 20) && (rand(20) == 0))
        {
            vy = rand(3) - 1;   //  -1, 0 or 1
            ticksSinceLastChangeY = 0;
        }

        // if moving would take us off the top or bottom of the water,
        // either reverse or go level
        if (((vy < 0) && (y + vy < 0)) ||
            ((vy > 0) && (y + fishHeight + vy > FishTankCanvas.waterHeight)))
        {
            if (rand(2) == 0)
            {
                vy = -vy;
            }
            else
            {
                vy = 0;
            }
            ticksSinceLastChangeY = 0;
        }

        // mostly continue as we are, but sometimes randomly change
        if ((ticksSinceLastChangeD > 10) && (rand(10) == 0))
        {
            z += rand(3) - 1;   //  -1, 0 or 1

            // If moving would take us out of the 'depth' of zs
            if ((z < 0) || (z == FishTankCanvas.NUM_PLANES))
            {
                if (rand(2) == 0)
                {
                    z = (z < 0) ? 0 : z - 1;
                }
                else
                {
                    z = (z < 0) ? 1 : z - 2;
                }
            }
            ticksSinceLastChangeD = 0;
        }

        x += vx;
        y += vy;
    }


    public void draw(Graphics g)
    {
        DirectGraphics dg = DirectUtils.getDirectGraphics(g);

        Image img = fishImage[type][frame];
        if (img != null)
        {
            if (vx < 0)
            {
                dg.drawImage(img, x, y, (Graphics.LEFT | Graphics.TOP),
                    DirectGraphics.FLIP_HORIZONTAL);
            }
            else
            {
                dg.drawImage(img, x, y, (Graphics.LEFT | Graphics.TOP), 0);
            }
        }

        frame = (frame + rand(2)) % FRAME_NUM;
    }


    int getZ()
    {
        return z;
    }


    static int rand(int scale)
    {
      return (random.nextInt() << 1 >>> 1) % scale;
    }
}