manbullets.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.game.*;
import javax.microedition.lcdui.*;
import java.util.Random;

/**
 * 子弹操作类
 */

public class ManBullets {

  private ManGameCanvas manGC;

  // 存储子弹信息
  private int[][] Locus;
  private Sprite Bullets; // 子弹图象
  private Random rnd; // 随机种子
  private int SWidth, SHeight; // 设备屏幕的宽度与高度

  //--- 构造函数 ----------------------------------------------------------------
  public ManBullets(ManGameCanvas manGC, Image img, int SWidth, int SHeight) {
    this.manGC = manGC;
    Bullets = new Sprite(img, img.getWidth(), img.getHeight());
    Bullets.setFrame(0);

    Locus = new int[20][5];
    rnd = new Random();
    this.SWidth = SWidth;
    this.SHeight = SHeight;
  }

  //--- 初始化运行轨迹 -----------------------------------------------------------
  public void InitBulletsLocus() {
    for (int i = 0; i < Locus.length; i++) {
      InitBulletLocus(i);
    }
  }

  //--- 初始化运行轨迹随机数组 ----------------------------------------------------
  private void InitBulletLocus(int i) {
    // 子弹的类型，0:上 1:下 2:左 3:右
    Locus[i][0] = (rnd.nextInt() & 0x7fffffff) % 4; //子弹类型
    switch (Locus[i][0]) {
      case 0:
        Locus[i][1] = -5; //子弹初始X坐标值
        Locus[i][2] = (rnd.nextInt() & 0x7fffffff) % SHeight; //子弹初始的Y坐标值
        Locus[i][3] = (rnd.nextInt() & 0x7fffffff) % 3 + 1; //vx子弹X坐标增量
        Locus[i][4] = (rnd.nextInt()) % 3; //vy子弹Y坐标增量
        break;
      case 1:
        Locus[i][1] = SWidth + 5;
        Locus[i][2] = (rnd.nextInt() & 0x7fffffff) % SHeight;
        Locus[i][3] = ( (rnd.nextInt() & 0x7fffffff) % 3 + 1) * -1;
        Locus[i][4] = (rnd.nextInt()) % 3;
        break;
      case 2:
        Locus[i][1] = (rnd.nextInt() & 0x7fffffff) % SWidth;
        Locus[i][2] = -5;
        Locus[i][3] = (rnd.nextInt()) % 3;
        Locus[i][4] = (rnd.nextInt() & 0x7fffffff) % 3 + 1;
        break;
      case 3:
        Locus[i][1] = (rnd.nextInt() & 0x7fffffff) % SWidth;
        Locus[i][2] = SHeight + 5;
        Locus[i][3] = (rnd.nextInt()) % 3;
        Locus[i][4] = ( (rnd.nextInt() & 0x7fffffff) % 3 + 1) * -1;
        break;
    }
  }

  //--- 显示子弹 ----------------------------------------------------------------
  public void paint(Graphics g, int planeX, int planeY) {
    for (int i = 0; i < Locus.length; i++) {
      if (isCollision(planeX, planeY, i, 10)) { // 碰撞判断
        if (!manGC.gameover) {
          manGC.gameover = true;
        }
        manGC.SpExplosion.setPosition(Locus[i][1] - 16, Locus[i][2] - 16);
        continue;
      }
      Bullets.setPosition(Locus[i][1], Locus[i][2]);
      Bullets.paint(g);
      UpdataBulletLocus(i); // 更新运行轨迹数组
    }
  }

  //--- 更新运行轨迹数组 ---------------------------------------------------------
  private void UpdataBulletLocus(int i) {
    Locus[i][1] += Locus[i][3];
    Locus[i][2] += Locus[i][4];
    //超出边界的处理
    if (Locus[i][1] < -5 || Locus[i][1] > SWidth + 5) {
      Locus[i][3] *= -1;
    }
    if (Locus[i][2] < -5 || Locus[i][2] > SHeight + 5) {
      Locus[i][4] *= -1;
    }
  }

  //--- 碰撞判断 ----------------------------------------------------------------
  private boolean isCollision(int planeX, int planeY, int i, int range) {
    boolean result = false;
    // 将飞机近似的看成圆，取得其圆心坐标
    int planeXCenter = planeX + 12;
    int planeYCenter = planeY + 12;
    // 同理，取得子弹的圆心坐标
    int bulletXCenter = Locus[i][1] + 3;
    int bulletYCenter = Locus[i][2] + 3;
    // 理由半径检测，小于10即已碰撞
    if (Math.abs(planeXCenter - bulletXCenter) < range) {
      if (Math.abs(planeYCenter - bulletYCenter) < range) {
        result = true;
      }
    }
    return result;
  }

  //--- 炸弹爆炸操作 ------------------------------------------------------------
  public void BombBullets(int planeX, int planeY) {
    for (int i = 0; i < Locus.length; i++) {
      if (isCollision(planeX, planeY, i, 32)) {
        InitBulletLocus(i);
      }
    }
  }

}