UIView cornerRadius-什么？

Question

I am familiar with the cornerRadius property of UIView layers, exposed with the QuartzCore framework. The general rule of thumb, of course, is larger values create more rounded edges, and smaller values create less rounded edges. I'm curious though, the property is called cornerRadius , and I often find myself asking, radius of what? What and where is this circle whose radius I'm changing?

Answer 1

Imagine a circle at each corner of the rectangle framing the view. The rounded edge of the corner follows the arc of the circle. cornerRadius is the radius of that circle.

Answer 2

Take the 4 corners of a rectangle.

Starting at the corner points, you pass it a length to which the rounded corner should extend to.

This is the radius of the corner, or cornerRadius.

That's how I interpret it. Don't know if that's correct :P

Answer 3

This is more of a math question, but the above answer is mostly correct, except that the lines aren't circular. A radius is:

A radial line from the focus to any point of a curve.

(Source: Oxford )

As an example, note the non-circular curvature of some non-circular gears , which still have radii.

So, it's similar to what's described in the other answers, but the corner curve is not circular. If you're curious about the equation of the curve, just do the radius equation backwards. :-)