Why iOS coordinate system is difficult to understand?? only me? - ios

Question

I'm studying iOS' UIView!
And I found that I can't understand how bounds works.
For example,
Please run this code ... and see red box's moving.
The red box goes up! and white root view is static!
Why!? why red box goes up! ?? please let me know OTL!
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
let childView : UIView = UIView(frame: CGRect(x: 50, y: 50, width: 200, height: 200) )
childView.backgroundColor = UIColor.red
self.view.addSubview(childView)
}
override func viewDidAppear(_ animated: Bool) {
UIView.animate(withDuration: 8, animations: {
// I cannot unnerstand how bounds works!!
self.view.bounds = CGRect(x: 0, y: -300, width:self.view.bounds.width, height: 700)
//I can understand how frame works
self.view.frame = CGRect(x: 200, y: 0, width: self.view.bounds.width, height: self.view.frame.height)
})
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
I read this article, but I can not understand
CompositedPosition.x = View.frame.origin.x - Superview.bounds.origin.x;
CompositedPosition.y = View.frame.origin.y - Superview.bounds.origin.y;
HERE! this is right ( according to what I tested, it was right. ) but, I don't know why. Why not "View.frame.origin.x + Superview.bounds.origin.x" ?
If we change the origin of view's bounds and the view moves on screen , what is the difference between "bounds" and "frame" in perspective of origin(or position) ? Is there a difference other than simply acting in reverse?

Answer 1

Basically, The bounds of an UIView is the rectangle, expressed as a location (x,y) and size (width,height) relative to its own coordinate system (0,0).
The frame of an UIView is the rectangle, expressed as a location (x,y) and size (width,height) relative to the superview it is contained within.
Please follow this link for clear example. Cocoa: What's the difference between the frame and the bounds?