java - 为什么 getHeight() 不等于框架高度？

Question

我正在制作一个围绕框架移动的弹跳立方体。为了检测框架的边界，我使用了 JFrame 中 JComponent 的 getHeight() 和 getWidth() 并计算可能的边界，以便立方体可以反弹。

它对 getWidth() 完全有效。但是，我无法让它在 getHeight() 的边界上反弹。

当立方体到达窗口顶部时，它会在反弹前继续移动大约 10 个像素。

这是这个问题的截图。

这是我的代码:

public class Cube {
    final public static int DIMENSION = 100;
    private final static int D_X = 20;
    private final static int D_Y = -20;
    private final static int SPEED = 1;
    private int xVelBK;
    private int yVelBK;
    private int xVel;
    private int yVel;
    private CubePoint[] pts;

    public  Cube(int x, int y){
    xVel = SPEED;
    yVel = SPEED;

    pts = new CubePoint[8];

    pts[0] = new CubePoint(x,y);
    pts[1] = new CubePoint(x,y - DIMENSION);
    pts[2] = new CubePoint(x + DIMENSION,y - DIMENSION);
    pts[3] = new CubePoint(x + DIMENSION,y);

    pts[4] = new CubePoint(x + D_X,y + D_Y);
    pts[5] = new CubePoint(x + D_X,y + D_Y - DIMENSION);
    pts[6] = new CubePoint(x + D_X + DIMENSION,y + D_Y - DIMENSION);
    pts[7] = new CubePoint(x + D_X + DIMENSION,y + D_Y);
    }

    public void move(int componentWidth, int componentHeight){
    ......

    //bug in here
    if (pts[0].getY()  - DIMENSION - D_Y <= 0 ) {
        yVel = SPEED;
    }

    .......
    }
..........
}

这是组件:

public class CubeComponent extends JComponent {
    ...........

    private Cube cube;
    private Timer timer;
    private CubePoint originMousePos;
    private CubePoint closest;
    private Font font;
    private int mode;


    private int delay = DEFAULT_DELAY ;

    private int mouseToClosestX;
    private int mouseToClosestY;

    class CubeMoveListener implements ActionListener{
    @Override
    public void actionPerformed(ActionEvent e){
        cube.move(getWidth(),getHeight());
        repaint();
    }

    }



    @Override
    public void paintComponent(Graphics g){
    Graphics2D g2 = (Graphics2D)g;

    cube.draw(g2);
    }

}

Answer 1

据我所知:

 if (pts[0].getY()  - DIMENSION - D_Y <= 0 ) {

应该用于确定立方体何时到达组件底部，因此您应该测试“>”

和

if ( pts[0].getY() >= componentHeight) {

应该在立方体到达顶部时用于测试。所以应该是:

if ( pts[0].getY() <= 0) {

重点在于:

1. 其中一个垂直测试需要测试“<= 0”。
2. 水平测试和垂直测试的结构应该是一样的，你只需要改变变量名。