ios - Using Autolayout Constraints programmatically to center a UIImageView inside a UIView Swift 2.3 iOS10 -

i have added uiview table cell through storyboard following constraints:

then have following code programmatically add uiimageview uiview above , size according orientation of screen.

            //use half screen size width when on iphone , on landscape             let image: uiimage = uiimage(named: header_image_bath)!             imageview = uiimageview(image: image)             imageview!.frame = cgrectmake(0 , 0, self.view.frame.width / 2, 185)             imageview!.contentmode = .scaleaspectfit             //center image             let centerxconst = nslayoutconstraint(item: imageview!, attribute: .centerx, relatedby: .equal, toitem: imagewrapperview, attribute: .centerx, multiplier: 1, constant: 1)             let centeryconst = nslayoutconstraint(item: imageview!, attribute: .centery, relatedby: .equal, toitem: imagewrapperview, attribute: .centery, multiplier: 1, constant: 1)             nslayoutconstraint.activateconstraints([centerxconst, centeryconst])             //add sub view             imagewrapperview.addsubview(imageview!) 

however, image not centered when in landscape. image half width of screen , center inside uiview. missing? thanks

1. you should use auto layout instead of frame width , height of imageview
2. you have add imageview imagewrapperview before add constraints
3. you have set imageview.translatesautoresizingmaskintoconstraints false

then, final code is:

    //use half screen size width when on iphone , on landscape     let image: uiimage = uiimage(named: "key.png")!     let imageview = uiimageview(image: image)     imageview.contentmode = .scaleaspectfit     imageview.translatesautoresizingmaskintoconstraints = false      //add sub view     imagewrapperview.addsubview(imageview)      //center image     let centerxconst = nslayoutconstraint(item: imageview, attribute: .centerx, relatedby: .equal, toitem: imagewrapperview, attribute: .centerx, multiplier: 1.0, constant: 0.0)     let centeryconst = nslayoutconstraint(item: imageview, attribute: .centery, relatedby: .equal, toitem: imagewrapperview, attribute: .centery, multiplier: 1.0, constant: 0.0)      let heightconstraint = nslayoutconstraint(item: imageview, attribute: .height, relatedby: .equal, toitem: nil, attribute: .notanattribute, multiplier: 1.0, constant: 185.0)     let widthconstraint = nslayoutconstraint(item: imageview, attribute: .width, relatedby: .equal, toitem: nil, attribute: .notanattribute, multiplier: 1.0, constant: self.view.frame.width / 2)     imageview.addconstraints([heightconstraint, widthconstraint])      nslayoutconstraint.activateconstraints([centerxconst, centeryconst])