Position Subviews Relative to Screen Estate - objective-c

Question

I'd like to display multiple small UIViews as Subviews relative to the screen estate. This should work across different screen sizes (iPad, iPhone)/portrait/landscape modes.
Each subview to display has two NSNumber objects with an unsigned int ranging from -100 (min) to 100 (max) which needs to be mapped to the correct x and y coordinates for positioning.
What's the best way to translate those values (-100...100) to use them for positioning UIViews on the screen?
How do I position them in a relative rather then an absolute way, so that the code works across screen rotation and screen sizes?

Answer 1

Ok, so if I understand correctly you want a -100 in the x direction to map to the left most point on the screen, 100 in the x to map to the right most point on the screen, -100 in the y direction to map to the lowest point on the screen, and 100 in the y to map to the highest point on screen (or maybe you want the y inverted from what I have so that it agrees with the screen coordinate system in which y becomes bigger the lower on the screen you get?).
And we also want to account for rotation.
As far as I understand it, asking UIScreen for its height and width:
CGFloat width = [UIScreen mainScreen].bounds.size.width;
CGFloat height = [UIScreen mainScreen].bounds.size.height;
but this does not account for rotation. The only other way I am aware of that is pretty straightforward would be to ask a UIView covering the screen for its width and height (most simply, you could make your viewcontroller's view cover the whole screen).
If you had a UIView that perfectly covered the whole screen (let's call it myView), you could try:
CGFloat width = myView.frame.size.width;
CGFloat height = myView.frame.size.height;
these should adjust for orientation by themselves (from my experience, it should definitely work if you get the height and width in viewDidAppear:animated: or anything after. also the UIView needs to either be the UIViewControllers view property or a subview of this view. if not, you'll have to implement didRotateFromInterfaceOrientation: or find some other way to tell your view about any rotations). Once we have the 'width' and 'height' of the screen, we can convert from your int's to screen position. Try something like:
(CGPoint)convertX:(NSNumber *)x andY:(NSNumber *)y intoPoint
{
pointX = ([x intValue] + 100.0)*width/200.0;
pointY = (-[y intValue] + 100.0)*height/200.0; // remove the - sign at the front of the expression for y to grow as you move down the screen
return CGPointMake(pointX, pointY);
}
to convert from -100 to 100 in x and y to their respective points on the screen.

Answer 2

If you're working with a range of +/-100, then you may want to use the underlying CALayers to position your views. The nice part about CALayers, is that their anchor points are mapped to a device-agnostic grid that ranges from 0.0 to +1.0 on a Cartesian plane.