在重绘中动画化多个球对象(一次一个)

Question

我有一个程序，我需要动画的球物体。我有一个Ball()类，它处理球向下下降时的移动，然后是动画()类，它绘制球和背景，然后使用定时器重新绘制球的移动时间。

我需要每个球的动画，然后球停止在屏幕底部，启动另一个球在屏幕顶部。我假设我需要一个Ball对象数组，这样当实例化一个新Ball时，球就不会消失。我的问题是，我不知道如何在代码中实例化另一个Ball对象。我尝试过多种方法，但都失败了。我终于得到了我的代码回到正常状态与一个工作球，并希望得到一些帮助！

最后注意:用户将从另一个菜单类中指定球的数量，然后将整数值传递给动画()类构造函数。我想使用这个整数值创建一个球数组。这是正确的思维方式吗？paintComponent()方法看不到构造函数中的数组，所以我必须创建一个方法将数组传递给paintComponent()？

动画类：

public class Animation extends JPanel implements ActionListener{

// Global Variables
private Timer timer;
Random rand = new Random();
private int delay = 0;
ActionListener updateAnim;
Ball myBall = new Ball();

// Animation Constructor
public Animation()
{
    timer = new Timer(delay,this);
    timer.setInitialDelay(500);
    timer.start();
}

// Ball will roll down/left/right
public void actionPerformed(ActionEvent e)
{       
    int x = rand.nextInt(2);
    myBall.rollDown();

    if (x == 0)
        myBall.rollRight();
    else
        myBall.rollLeft();

    myBall.finalDescent();
    repaint();
}

// Draws Ball object, and Background
public void paintComponent(Graphics g)
{
    super.paintComponent(g);
    myBall.drawBall(g);

    this.setBackground(Color.WHITE); // Background

    int counter = 0; // count what number peg we are painting
    int row = 1;     // calculate what row we are creating
    int rowSpacer = 55;
    boolean evenRow = false;
    int columnSpacer = 60;

    // DRAW PEGS TO SCREEN (4 rows of 8, 4 rows of 7)
    for (int x = 0; x < 60; x++)
    {
        // For odd rows
        if (row % 2 == 1)
        {
            g.setColor(Color.BLACK);
            g.fillOval(rowSpacer - 40, columnSpacer, 10, 10);
            rowSpacer += 40;
            counter++;
        }
        // For Even rows
        else 
        {
            g.setColor(Color.BLACK);
            g.fillOval(rowSpacer - 20, columnSpacer, 10, 10);
            rowSpacer += 40;
            counter++;
        }

        // Check to see if we are finished with odd row
        if (counter % 8 == 0 && evenRow == false)
        {
            row++;
            rowSpacer = 55;
            columnSpacer += 60;
            evenRow = true;
            counter = 0;
        }
        else if(counter % 7 == 0 && evenRow == true) 
        {
            row++;
            rowSpacer = 55;
            columnSpacer += 60;
            evenRow = false;
            counter = 0;
        }
    } // END DRAWING PEGS TO SCREEN

    // DRAW RECTANGULAR WALLS TO SCREEN
    g.setColor(Color.BLACK);    // Wall Color
    g.fillRect(0, 0, 5, 760);   // LEFT Wall
    g.fillRect(315, 0, 5, 760); // RIGHT Wall
    //g.fillRect(0, 0, 315, 5);   // TOP Wall
    g.fillRect(0, 755, 320, 5); // BOTTOM Wall

    // DRAW BOTTOM GATES
    int gateSeperator = 35;
    for (int x = 0; x < 7; x++)
    {
        g.setColor(Color.BLACK);
        g.fillRect(gateSeperator, 500, 10, 255);
        gateSeperator += 40;
    }   

    } // END paintComponent()
} // END Animation Class

球类：

public class Ball{

private int x = 85, y = -30;
private int velx = 0, vely = 0;
private boolean downInMotion = false;
private boolean rightInMotion = false;
private boolean leftInMotion = false;
private boolean ballStopped = false;
private boolean finalDescent = false;
private boolean horizontalLast = true;
private int hCounter = 0, vCounter = 0;
private int traveled = 0;

public void moveBall(int xPos, int yPos)
{
    x = xPos;
    y = yPos;
}

public int getX()
{
    return x;
}

public int getY()
{
    return y;
}

public void rollDown()
{
    if(leftInMotion == false && rightInMotion == false && ballStopped == false
            && finalDescent == false && horizontalLast == true)
    {
        downInMotion = true;
        vely = 1;
        velx = 0;

        if (traveled == ((vCounter + 60) + hCounter))
        {
            vely = 0;
            downInMotion = false;
            horizontalLast = false;
            vCounter += 60;
            System.out.println("Turning Right");
        }
        else
        {
            moveBall(x, y + vely);
            traveled += 1;
            System.out.println("Traveled: " + traveled);
        }
    }
} // END rollDown()

// The Ball will roll to the right
public void rollRight()
{
    if (leftInMotion == false && downInMotion == false && ballStopped == false 
            && finalDescent == false && horizontalLast == false)
    {
        rightInMotion = true;
        vely = 0;
        velx = 1;

        if (traveled == (vCounter + (hCounter + 20)))
        {
            velx = 0;
            rightInMotion = false;
            horizontalLast = true;
            hCounter += 20;
            System.out.println("Going Down");
        }
        else
        {
            moveBall(x + velx, y);
            traveled += 1;
            System.out.println("Traveled: " + traveled);
        }
    }
} // END rollRight()

public void rollLeft()
{
    if (rightInMotion == false && downInMotion == false && ballStopped == false
            && finalDescent == false && horizontalLast == false)
    {
        leftInMotion = true;
        vely = 0;
        velx = -1;

        if (traveled == (vCounter + (hCounter + 20)))
        {
            velx = 0;
            leftInMotion = false;
            horizontalLast = true;
            hCounter += 20;
            System.out.println("Turning Right");
        }
        else
        {
            moveBall(x + velx, y);
            traveled += 1;
            System.out.println("Traveled: " + traveled);
        }
    }
} // END rollLeft()

public void finalDescent()
{
    if (traveled >= 640 && ballStopped == false)
    {           
        finalDescent = true;

        vely = 1;
        velx = 0;

        System.out.println("FINAL DESCENT");

        if (traveled == 915)
        {
            vely = 0;
            System.out.println("Ball Stopped");
            stopBall();
        }
        else
        {
            moveBall(x, y + vely);
            traveled += 1;
            System.out.println("Traveled: " + traveled);
        }
    }
} // END finalDescent()

public void stopBall()
{
    ballStopped = true;
}

public void drawBall(Graphics g)
{
    g.setColor(Color.GREEN);
    g.fillOval(x, y, 30, 30);

}
}

Answer 1

你可能忘了把每个球都实例化了.

//declare a field
private List<Ball> balls;

Animation(int count) {
  balls = new ArrayList<Ball>();
  for (int i = 0; i < count; ++i) {
    //this is probably what you've missed...
    balls.add(new Ball());
  }
}


...
public void paintComponent(Graphics g)
  ...
  //paint as usual
  for (int i = 0; i < balls.length; ++i) {
    //this is probably what you've missed...
    balls[i].drawBall(g);
  }
}

...
public void someMethod() {
    if (youWantToAddBall) {
        balls.add(new Ball());
    }
    if (youWantToRemoveBall) {
        Ball ballToRemove = ...; //
        balls.remove(ballToRemove);
    }
}

编辑:我更仔细地阅读了你的问题，下面是一些更多的想法。我认为把流动球和其他球分开比较好。所以你可以把它们分开移动，但仍然可以完全画出来。此外，您还需要向Ball类添加check方法，以确定是否删除了球。

List<Ball> movingBalls = new ArrayList<Ball>();
List<Ball> allBalls = new ArrayList<Ball>();

Animation(int count) {
  balls = new ArrayList<Ball>();
  for (int i = 0; i < count; ++i) {
    Ball newBall = new Ball();

    allBalls.add(newBall);
    //all new balls are initially moving
    movingBalls.add(newBall);
  }
}

// Ball will roll down/left/right
public void actionPerformed(ActionEvent e) {       
    // we need to use new list here, because we can't add to movingBalls list, while iterating
    List<Ball> newBalls = new ArrayList<Ball>();

    //using iterators here, so we can remove balls, while iterating
    Iterator it = movingBalls.iterator()
    while (it.hasNext()) {
      Ball ball = it.next();

      int x = rand.nextInt(2);
      ball.rollDown();

      if (x == 0)
          ball.rollRight();
      else
          ball.rollLeft();

      ball.finalDescent();

      //now check if ball is dropped and create new one...
      if (ball.isDropped()) {
        //remove current ball from movingBalls list
        it.remove(); 

        //create new ball
        newBalls.add(new Ball());
      }
    }

    movingBalls.addAll(newBalls);
    allBalls.addAll(newBalls);

    repaint();
}

public void paintComponent(Graphics g)
  ...
  //paint as usual
  for (int i = 0; i < allBalls.length; ++i) {
    //this is probably what you've missed...
    allBalls[i].drawBall(g);
  }
}