How to apply auto layout properly - ios

Question

I have set of images(thumbs) in UITableviewcell. When tapping on each image, a popup(custom view) will be displayed which is a UISCrollview. i am adding all images(big) in Scroll View. So user can scroll to see images.
I am adding UISCrollView to RootViewController's view. so that it covers the entire screen. Below is my code
My Code:
self.mainView = self.superview?.window?.rootViewController?.view
imageScrollView = UIScrollView(frame: CGRectMake(0, 0, self.mainView!.frame.size.width, self.mainView!.frame.size.height))
imageScrollView.delegate = self
self.mainView.addsubview(imageScrollView)
Constraints:
self.mainView!.addConstraint(NSLayoutConstraint(item: imageScrollView, attribute: NSLayoutAttribute.CenterX, relatedBy: NSLayoutRelation.Equal, toItem: self.mainView!, attribute: NSLayoutAttribute.CenterX, multiplier: 1.0, constant: 0.0))
self.mainView!.addConstraint(NSLayoutConstraint(item: imageScrollView, attribute: NSLayoutAttribute.CenterY, relatedBy: NSLayoutRelation.Equal, toItem: self.mainView!, attribute: NSLayoutAttribute.CenterY, multiplier: 1.0, constant: 0.0))
I got the error in console:
Probably at least one of the constraints in the following list is one you don't want. Try this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints)
(
"<NSAutoresizingMaskLayoutConstraint:0xab1090 h=--- v=--- H:[UIWindow:0xa724f0(768)]>",
"<NSLayoutConstraint:0x1133f450 UIScrollView:0x115723a0.centerY == UIView:0xa49fe0.centerY>",
"<NSAutoresizingMaskLayoutConstraint:0x483cc70 h=--& v=--& UIScrollView:0x115723a0.midY == + 512>",
"<NSAutoresizingMaskLayoutConstraint:0x115b7290 h=-&- v=-&- UIView:0xa49fe0.width == UIWindow:0xa724f0.width>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x1133f450 UIScrollView:0x115723a0.centerY == UIView:0xa49fe0.centerY>
Break on objc_exception_throw to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.
2014-12-08 01:13:27.379 afipad[349:60b] Unable to simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you don't want. Try this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints)
(
"<NSAutoresizingMaskLayoutConstraint:0xab10c0 h=--- v=--- V:[UIWindow:0xa724f0(1024)]>",
"<NSLayoutConstraint:0x1133f090 UIScrollView:0x115723a0.centerX == UIView:0xa49fe0.centerX>",
"<NSAutoresizingMaskLayoutConstraint:0x115b6dd0 h=--& v=--& UIScrollView:0x115723a0.midX == + 384>",
"<NSAutoresizingMaskLayoutConstraint:0x115b72f0 h=-&- v=-&- UIView:0xa49fe0.height == UIWindow:0xa724f0.height>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x1133f090 UIScrollView:0x115723a0.centerX == UIView:0xa49fe0.centerX>
Break on objc_exception_throw to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.
When i check with break point, i got UIWindow size as 768 and 1024 in both portrait and Landscape. When i rotate the screen from Portrait to Landscape, the "imageScrollView" size is 768(width) and 1024(height) instead of 1024x768. What is the actual cause? How can i resolve it.

Answer 1

There are a couple different conflicting things happening here.
First, adding a subview to the root ViewController's view probably isn't going to work because it breaks encapsulation on several levels. Instead, present a new view controller containing your scrollView -- either as a modal or by pushing from self.navigationController -- directly from your table cell.
Second, autolayout constraints on UIScrollviews are kinda counterintuitive. See https://developer.apple.com/library/ios/technotes/tn2154/_index.html for an explanation of how to set them up.
Third, you'll probably need to set translatesAutoresizingMaskIntoConstraints to FALSE in this new viewController. (It explains that in the document, too)
Also, see my sample project for some examples of how to put images and other things inside a scrollView using autolayout:
https://github.com/annabd351/AutolayoutTemplate