我如何遍历对象的ArrayList以创建条件？

Question

我想要让我的最后一个IF循环遍历PinballTypeOne列表中的三个对象，只有在ArrayList中的这三个对象在它们碰到左墙后才能将它们以前的颜色更改为橙​​色。碰撞确实有效，但对象不会变为橙色，因此我认为我可能对ArrayList的创建方式或者我试图通过ArrayList进行迭代时存在问题。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

为了您的功能打动你应该这样做：

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); 
    } 
} 

，你需要覆盖，因为你使用自己定义的类（PinballObject）等于和的hashCode方法，请参阅this question。

我对你的问题PinballTypeOneList为什么它在PinballObject类？这意味着每一个PinballObject都有它，这听起来很糟糕...您需要制作PinballTypeOneList global然后在其中存储您的PinballObject s，或者您有特殊的理由这样做？

在此之后，我相信你的代码应该工作（虽然我没看到大部分代码）。