CGRect coordinates in non-retina form when using SetFrame

Question

I have a ViewController to which I applied the retina 3.5" form factor in the story board. The iOS iPhone 6.1 simulator also has the Retina configured.
When I try to position a UIImageView using SetFrame, its CGRect coordinates are in the non-retina form (i.e. when I position to 320x480, it goes to the bottom right instead of the middle of the screen):

[myImageView setFrame:CGRectMake(320, 480, myImageView.frame.size.width, myImageView.frame.size.height)];
[self.view addSubview:myImageView];

How to have CGRect coordinates for Retina when using SetFrame ?
Thanks.

Answer 1

The reason for this is because iOS uses points instead of pixels. This way, the same code will work on a retina and a non-retina screen. Therefore, when you set the location to (320,480) you are setting it to point (320,480) not pixel (320,480). This way, if the phone is non-retina, that point will end up being pixel (320, 480) and on retina, it will end up being pixel (640,960).

So what it looks like you want is:

[myImageView setFrame:CGRectMake(160, 240, myImageView.frame.size.width, myImageView.frame.size.height)];
[self.view addSubview:myImageView];

which will place the imageView's top-left corner in the same location on both retina and normal display.

Answer 2

To center a view:

CGFloat x = self.view.frame.size.width;
CGFloat h = self.view.frame.size.height;
[myImageView setCenter:CGPointMake(w/2, h/2)];
...
[self.view addSubview:myImageView];

CGRectMake needs a x,y,width,height.. X,y are the topleft of the view, so use 0,0,w,h for full frame views.