如何遍历对象的 ArrayList 以创建条件？

Question

我试图让我的最后一个 IF 循环遍历其中的三个对象 PinballTypeOne 列表中，只有 ArrayList 中的这三个对象在撞到左墙后才应将其原来的颜色更改为橙​​色。碰撞确实有效，但对象会不断反弹而不会变为橙色，所以我认为我可能对 ArrayList 的制作方式或我如何尝试遍历 ArrayList 有问题。没有编译错误。

   public class PinballObject
{
    private int currentXLocation;
    private int currentYLocation;
    private int speedXTravel;
    private int speedYTravel;
    private Color colour;
    private int radius;
    private Machine machine;
    private final int leftWallPosition;
    private final int bottomWallPosition;
    private final int topWallPosition;
    private final int rightWallPosition;
    private ArrayList<PinballObject> PinballTypeOneList = new ArrayList<PinballObject>();




    /**
     * Constructor for objects of class Pinball_Obj
     * 
     * @param xPos  the horizontal coordinate of the object
     * @param yPos  the vertical coordinate of the object
     * @param xVel  the horizontal speed of the object
     * @param yVel  the vertical speed of the object
     * @param objectRadius  the radius (in pixels) of the object
     * @param objectColor  the color of the object
     * @param theMachine  the machine this object is in
     */
    public PinballObject(int xPos, int yPos, int xVel, int yVel, Color objectColor, int objectRadius, Machine theMachine)
    {
        currentXLocation = xPos;
        currentYLocation = yPos;
        speedXTravel = xVel;
        speedYTravel = yVel;
        colour = objectColor;
        radius = objectRadius;
        machine = theMachine;
        leftWallPosition = machine.getLeftWall();
        bottomWallPosition = machine.getBottomWall();
        topWallPosition = machine.getTopWall();
        rightWallPosition = machine.getRightWall();
    }

    public void makeType1()
    {
        PinballObject firstTypeOne = new PinballObject(50, 200, -5, 3, Color.RED, 10, machine);
        PinballTypeOneList.add(firstTypeOne);

        PinballObject secondTypeOne = new PinballObject(100, 300, 1, 2, Color.BLUE, 55, machine);
        PinballTypeOneList.add(secondTypeOne);

        PinballObject thirdTypeOne = new PinballObject(450, 125, -1, -1, Color.YELLOW, 40, machine);
        PinballTypeOneList.add(thirdTypeOne);
    }


    /**
     * Move this object according to its position and speed and redraw.
     **/
    public void move()
    {
         // remove from universe at the current position
        machine.erase(this);

        // compute new position
        currentYLocation += speedYTravel;
        currentXLocation += speedXTravel;

        // check if it has hit the leftwall + change color to orange only for the objects IN the arraylist
        if(currentXLocation <= (leftWallPosition + radius)) 
        {
            currentXLocation = leftWallPosition + radius;
            speedXTravel = -speedXTravel;

            if(this.equals(PinballTypeOneList)){
                colour = Color.ORANGE;
            }

            // draw again at new position
         machine.draw(this);

        }
    }

Answer 1

对于您的功能移动，您应该这样做：

public void move()
{
    machine.erase(this);

    currentYLocation += speedYTravel;
    currentXLocation += speedXTravel;

    if(currentXLocation <= (leftWallPosition + radius)) 
    {
        currentXLocation = leftWallPosition + radius;
        speedXTravel = -speedXTravel;
        for(PinballObject po : PinballTypeOneList) { //Iterating through list of PinballObject's
            if(this.equals(po)) { // If this PinballObject is in list
                colour = Color.ORANGE; // Or use po.colour
            }
        }
        machine.draw(this);
    }
}

并且您需要覆盖 equals 和 hashCode 方法，因为您使用自己定义的类（PinballObject），请参阅this question。

我对您的 PinballTypeOneList 有疑问，为什么它在 PinballObject 类中？这意味着每个PinballObject 都有它，这听起来很糟糕...您需要将 PinballTypeOneList 设为全局，然后将您的PinballObjects 存储在其中，或者您有特殊的理由这样做？

在此之后，我相信您的代码应该可以工作。（虽然我没有看到大多数代码）。