J2ME 2D - 碰撞检测

Question

我正在创建自己的手机游戏：2D图形，由士兵移动和射击。我遇到了问题。我有两个TiledLayer。首先是地面，第二个包含墙壁，树木等。如何检测放置在2nd TiledLayer上的这些物体的碰撞？我试过了：如果发生碰撞继续向后移动。这是不对的。我正在前进，这里是墙：按UP - 好吧，士兵走了。但是当按下LEFT士兵时，尽管它应该左转（我知道因此已经编写了代码）。

然而，它是如何写的？

 public void run() {
   while(true) {
    int keyState = getKeyStates();
       if ((keyState & LEFT_PRESSED) != 0) {
           soldier.setTransform(Sprite.TRANS_ROT270);
            if(!(soldier.collidesWith(traps, false))) {
             soldier.move(-10, 0);
           } else {
        if((keyState & LEFT_PRESSED) != 0) soldier.move(10, 0);
    }
  }  else if ((keyState & UP_PRESSED) != 0) {
      soldier.setTransform(Sprite.TRANS_NONE);
       if(!(soldier.collidesWith(traps, false))) {
        soldier.move(0, -10);
       } else {
        if((keyState & UP_PRESSED) != 0) soldier.move(0, 10);
    }
  }  else if ((keyState & DOWN_PRESSED) != 0) {
      soldier.setTransform(Sprite.TRANS_ROT180);
       if(!(soldier.collidesWith(traps, false))) {
        soldier.move(0, 10);
       } else {
        if((keyState & DOWN_PRESSED) != 0) soldier.move(0, -10);
    }
  }  else if ((keyState & RIGHT_PRESSED) != 0) {
      soldier.setTransform(Sprite.TRANS_ROT90);
       if(!(soldier.collidesWith(traps, false))) {
        soldier.move(10, 0);
       } else {
        if((keyState & RIGHT_PRESSED) != 0) soldier.move(-10, 0);
    }
  } else if((keyState & FIRE_PRESSED) != 0) {
    createBullet();
  }

Answer 1

考虑simplifying your code并添加日志记录语句，以便更轻松地调试您描述的问题。

  

......怎么写？

以下是关于我如何......

rewrite "it" before even attempting to drill...

...在the code snippet provided in question的特定角落出现了什么问题：

public void run() {
    while (true) {
        // extract method:
        handle(getKeyStates(), soldier.collidesWith(traps, false));
    }
}

private void log(String msg) { System.out.println(msg); } // simplify logging

private void moveSoldier(int dx, int dy) {
    // extract method to simplify logging
    System.out.println("move soldier, dx = [" + dx + "], dy = [" + dy + "]");
    soldier.move(dx, dy);
}

private void handle(int keyState, boolean soldierCollidesWithTraps) {
    // IMPL NOTE below code could (should) be refactored further
    if ((keyState & LEFT_PRESSED) != 0) {
        // IMPL NOTE consider extracting this block into dedicated method
        log("left pressed"); // log useful information
        soldier.setTransform(Sprite.TRANS_ROT270);
        if (!soldierCollidesWithTraps) {
            log("no collision");
            moveSoldier(-10, 0);
            return; // return as soon as we think we're done
        }
        // because of 'return' above, 'else' here is not needed anymore
        if ((keyState & LEFT_PRESSED) != 0) {
            log("left pressed - why re-check it here?");
            moveSoldier(10, 0);
            return;
        }
        log("no move"); // IMPL NOTE seems to be bug in your code logic above
        return;
    }
    if ((keyState & UP_PRESSED) != 0) {
        log("up pressed");
        soldier.setTransform(Sprite.TRANS_NONE);
        if (!soldierCollidesWithTraps) {
            log("no collision");
            moveSoldier(0, -10);
            return;
        }
        if ((keyState & UP_PRESSED) != 0) {
            log("up pressed - why re-check it here?");
            moveSoldier(0, 10);
            return;
        }
        log("no move"); // IMPL NOTE seems to be bug in your code logic above
        return;
    }
    if ((keyState & DOWN_PRESSED) != 0) {
        log("down pressed");
        soldier.setTransform(Sprite.TRANS_ROT180);
        if (!soldierCollidesWithTraps) {
            log("no collision");
            moveSoldier(0, 10);
            return;
        }
        if ((keyState & DOWN_PRESSED) != 0) {
            log("down pressed - why re-check it here?");
            moveSoldier(0, -10);
            return;
        }
        log("no move"); // IMPL NOTE seems to be bug in your code logic above
        return;
    }
    if ((keyState & RIGHT_PRESSED) != 0) {
        log("right pressed");
        soldier.setTransform(Sprite.TRANS_ROT90);
        if (!soldierCollidesWithTraps) {
            log("no collision");
            moveSoldier(10, 0);
            return;
        }
        if ((keyState & RIGHT_PRESSED) != 0) {
            log("right pressed - why re-check it here?");
            moveSoldier(-10, 0);
            return;
        }
        log("no move"); // IMPL NOTE seems to be bug in your code logic above
        return;
    }
    if ((keyState & FIRE_PRESSED) != 0) {
        log("fire pressed");
        createBullet();
        return;
    }
    log("no action");
}