Question

I want to position 10 JPanels in a Circle. Every Panel has the same size and the length between two Panels should be the same. So the easiest way i thought is to grab a null-Layout and compute the bounding box by hand via polarcoordiantes:

JPanel panel = new JPanel(null);

int r = 100;
int phi = 90;

for (int i = 0; i < 10; i++) {
    JPanel x = new JPanel();
    x.setBackground(Color.red);
    x.setBounds((int) (r * Math.sin(phi)) + 100, (int) (r * Math.cos(phi)) + 100, 4, 4);

    panel.add(x);
    phi = (phi + 36) % 360;
}

But that doesnt work! Some items are on the circle, some of them are pixels off… i have a bsolutly no idea why?!
I also cant find a LayoutManager that can do that for me, so what to do?

Answer 1

Your code is good, but you’ve missed one very important piece of information – the trigonometric functions expect angles in radians not degrees.

Wrap the evaluation of phi in Math.toRadians(double), and you’ll get the layout you expect.

(On a side note, I’ve been thinking about how to do something like this, thanks for the example)