microtanksprite.java

本光盘是《J2ME无线移动游戏开发》一书的配套光盘

package ch08;

import javax.microedition.lcdui.*;
import javax.microedition.lcdui.game.*;

public class MicroTankSprite
    extends Sprite {
  private int mDirection;
  private int mKX, mKY;

  private int mLastDelta;
  private boolean mLastWasTurn;

  private static final int[] kTransformLookup = {
      Sprite.TRANS_NONE, Sprite.TRANS_NONE, Sprite.TRANS_NONE,
      Sprite.TRANS_MIRROR_ROT90,
      Sprite.TRANS_ROT90, Sprite.TRANS_ROT90, Sprite.TRANS_ROT90,
      Sprite.TRANS_MIRROR_ROT180,
      Sprite.TRANS_ROT180, Sprite.TRANS_ROT180, Sprite.TRANS_ROT180,
      Sprite.TRANS_MIRROR_ROT270,
      Sprite.TRANS_ROT270, Sprite.TRANS_ROT270, Sprite.TRANS_ROT270,
      Sprite.TRANS_MIRROR
  };

  private static final int[] kFrameLookup = {
      0, 1, 2, 1,
      0, 1, 2, 1,
      0, 1, 2, 1,
      0, 1, 2, 1
  };

  private static final int[] kCosLookup = {
      0, 383, 707, 924,
      1000, 924, 707, 383,
      0, -383, -707, -924,
      -1000, -924, -707, -383
  };

  private static final int[] kSinLookup = {
      1000, 924, 707, 383,
      0, -383, -707, -924,
      -1000, -924, -707, -383,
      0, 383, 707, 924
  };

  public MicroTankSprite(Image image, int frameWidth, int frameHeight) {
    super(image, frameWidth, frameHeight);
    defineReferencePixel(frameWidth / 2, frameHeight / 2);
    mDirection = 0;
  }

  public void turn(int delta) {
    mDirection += delta;
    if (mDirection < 0) {
      mDirection += 16;
    }
    if (mDirection > 15) {
      mDirection %= 16;

    }
    setFrame(kFrameLookup[mDirection]);
    setTransform(kTransformLookup[mDirection]);

    mLastDelta = delta;
    mLastWasTurn = true;
  }

  public void forward(int delta) {
    fineMove(kCosLookup[mDirection] * delta,
             -kSinLookup[mDirection] * delta);
    mLastDelta = delta;
    mLastWasTurn = false;
  }

  public void undo() {
    if (mLastWasTurn) {
      turn( -mLastDelta);
    }
    else {
      forward( -mLastDelta);
    }
  }

  private void fineMove(int kx, int ky) {
    // First initialize mKX and mKY if they're
    // not close enough to the actual x and y.
    int x = getX();
    int y = getY();
    int errorX = Math.abs(mKX - x * 1000);
    int errorY = Math.abs(mKY - y * 1000);
    if (errorX > 1000 || errorY > 1000) {
      mKX = x * 1000;
      mKY = y * 1000;
    }
    // Now add the deltas.
    mKX += kx;
    mKY += ky;
    // Set the actual position.
    setPosition(mKX / 1000, mKY / 1000);
  }
}