Using convertPoint to get the relative position inside a parent UIView

http://stackoverflow.com/questions/15883305/using-convertpoint-to-get-the-relative-position-inside-a-parent-uiview

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I've looked at a dozen SO questions on this topic, and none of the answers have worked for me. Maybe this will help get me back on the right path.

Imagine this setup:

I want to get the center coordinates of the UIButton relative to the UIView.

In other words, the UIButton center may be 215, 80 within the UITableViewCell, but relative to the UIView they should be more like 260, 165. How do I convert between the two?

Here's what I've tried:

[[self.view superview] convertPoint:button.center fromView:button]; // fail[button convertPoint:button.center toView:self.view]; // fail[button convertPoint:button.center toView:nil]; // fail[button convertPoint:button.center toView:[[UIApplication sharedApplication] keyWindow]]; // failI could do it the hard way by looping through all of the button's superviews and adding up the x and y coordinates, but I suspect that's overkill. I just need to find the right combination of covertPoint settings. Right?

ios objective-c

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asked Apr 8 '13 at 15:37

Axeva

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It will help if you add the following to your question: The frames of all 4 views in your image, the output you get from the methods you have tried, and the value you actually want. – rmaddy Apr 8 '13 at 15:43

2 Answers

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button.center is the center specified within the coordinate system of its superview, so I assume that the following works:

CGPoint p = [button.superview convertPoint:button.center toView:self.view]Or you compute the button's center in its own coordinate system and use that:

CGPoint buttonCenter = CGPointMake(button.bounds.origin.x + button.bounds.size.width/2, button.bounds.origin.y + button.bounds.size.height/2);CGPoint p = [button convertPoint:buttonCenter toView:self.view];

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edited Apr 8 '13 at 15:51

answered Apr 8 '13 at 15:45

Martin R

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Bingo! Your first attempt was what I was looking for. The center being tied to the coordinate system of the superview is what I was missing. Thank you! – Axeva Apr 8 '13 at 16:10

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Martin answer is correct. For developers using Swift, you can get the position of an object (button, view,...) relative to the screen by using:

var p = obj.convertPoint(obj.center, toView: self.view)println(p.x) // this prints the x coordinate of 'obj' relative to the screenprintln(p.y) // this prints the y coordinate of 'obj' relative to the screen

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edited Jul 27 at 3:59

answered Nov 19 '14 at 7:01

RSC

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