How do I add a UIview to an imageView while ensuring that the contents of the UIView are inside the it's frame?

Question

I have a superview which contains a ImageView, a testView, and some buttons. I created a UIView which contains ImageView2

Answer 1

The problem is that lines like this do not do what you think:

let rect = CGRect(x: self.imageView.center.x-30, y: self.imageView.center.y-30, width: 80, height: 80)
// ... and ...
imageView2.center = testview.center

The center of a view is in its frame coordinates - it has to do with how the view is placed in its superview. But the position of a subview must be described in terms of its superviews bounds, not its frame. Its bounds are its internal coordinates, which is what you want.

Let's take the simplest case: how to center a subview in a superview. This is not the way:

imageView2.center = testview.center

You see the problem? testview.center is where testview is located in its superview; it is not the internal center of testview, which is what you want. The internal center of testview comes from its bounds. This is the way:

let c = CGPointMake(testview.bounds.midX, testview.bounds.midY)
imageView2.center = c