Java:用递归画圆

Question

所以我试图让我的程序通过递归来画圆圈。每次它进入递归时，圆的半径应该增加 10。它应该是这样的:

但是当我运行这段代码在面板上绘制时:

class CirclePanel extends JPanel{
public int radius = 25;
int xPossition = 250;
int yPossition = 250;
    @Override
public void paintComponent(Graphics g){
    super.paintComponents(g);

    g.setColor(Color.BLUE);
    g.drawOval(250, 250, radius, radius);
    radius += 10;

    if (radius + 10 < 250){
    paintComponent(g);
    }
    }


}

我明白了:

如果我将圆心设置为常量 250，为什么圆心会发生变化？

Answer 1

因为在 documentation 上指定

x - the x coordinate of the upper left corner of the oval to be drawn.

y - the y coordinate of the upper left corner of the oval to be drawn.

width - the width of the oval to be drawn.

height - the height of the oval to be drawn.

如果 x 和 y 是圆心的坐标，您的代码就可以运行

您应该像这样调整您的代码:

class CirclePanel extends JPanel{
  public int radius = 25;
  int xPossition = 250;
  int yPossition = 250;

  @Override
  public void paintComponent(Graphics g){
      super.paintComponents(g);
      g.setColor(Color.BLUE);
      g.drawOval(250-(radius/2), 250-(radius/2), radius, radius);
      radius += 10;

      if (radius + 10 < 250){
        paintComponent(g);
      }
  }
}