Auto-Layout animation takes center as anchoring point

Question

I have an height animation based on constraints. However when animation starts it takes view's center as anchoring point not the top.

I want it to animate as fixed top and shrinking from the bottom.

Sorry for my English not a native speaker.

my views anchors:

top: superview
left: superview
right: superview
bottom: nil

// current height constant 200
view.height.constant = 0

UIView.animation(withDuration: 0.2, animations: {
    view.layoutIfNeded()
}}

Answer 1

Try instead of your view:

superView.layoutIfNeeded()

this will layout the subview and your animation should work.

so replace

    // current height constant 200
view.height.constant = 0

UIView.animation(withDuration: 0.2, animations: {
    view.layoutIfNeded()
}

with

    // current height constant 200
yourView.height.constant = 0

UIView.animation(withDuration: 0.2, animations: {
    yourViewSuperview.layoutIfNeded()
}

see layoutIfNeeded() apple docs: [1]https://developer.apple.com/documentation/uikit/uiview/1622507-layoutifneeded