以编程方式更改情节提要视图的高度

Question

Background:

I have a normal UIView in Storyboard (called statusView ) which has a height of 30 , and four constraints pinned to the leading, trailing, top space to the superview, and bottom space to the view below it.

Problem:

My goal is to alter the height of statusView , including animating the frame changes when the user performs an action. As such, statusView could be as short as 0 or as tall as 100 .

My expectation is that, given statusView is constrained to the superview and its nearest neighbor below, it should automatically "push" the views below when I alter its height.

Just to test, in viewDidAppear , I call the following:

self.statusView.frame = CGRect(x: 0, y: 0, width: self.view.frame.size.width, height: 100.0)
self.statusView.setNeedsDisplay()

Issue : However, the height of 30 remains for statusView , despite me setting it to 0 .

Edit: posted Storyboard settings

This is the setting for statusView :

Answer 1

If you are using autolayout and want to set an explicit height for a view in your hierarchy, you should use autolayout to do it. I am assuming there is a height constraint set up in interface builder.

Create an IBOutlet for the constraint and link it up in interface builder.

@IBOutlet weak var statusViewHeightConstraint: NSLayoutConstraint!

Then, assuming this is just a size constraint with a constant for the height, just change it in your code:

statusViewHeightConstraint.constant = 100

You can animate this change by wrapping a layout call in an animation block right after modifying your constraint(s). Something like this:

UIView.animateKeyframes(withDuration: 0.2, delay: 0.0, options: [.beginFromCurrentState, .calculationModeCubic], animations: {
  self.view.layoutIfNeeded()
}, completion: nil)