在iOS9.0中对锚定样式约束进行动画处理

Question

使用锚样式NSLayoutConstraints（如在此答案：Swift |通过编程添加约束）如何为子视图设置动画？

对于那些懒惰的人，这里的代码是：

override func viewDidLoad() {
    super.viewDidLoad()

    let newView = UIView()
    newView.backgroundColor = UIColor.redColor()
    newView.translatesAutoresizingMaskIntoConstraints = false
    view.addSubview(newView)

    let horizontalConstraint = newView.centerXAnchor.constraintEqualToAnchor(view.centerXAnchor)
    let vertivalConstraint = newView.centerYAnchor.constraintEqualToAnchor(view.centerYAnchor)
    let widthConstraint = newView.widthAnchor.constraintEqualToAnchor(nil, constant: 100)
    let heightConstraint = newView.heightAnchor.constraintEqualToAnchor(nil, constant: 100)
    NSLayoutConstraint.activateConstraints([horizontalConstraint, vertivalConstraint, widthConstraint, heightConstraint])
}

具体来说，如果我想newView向右滑动，该怎么做？谢谢。

Answer 1

您将设置约束，然后在动画块中，使用layoutIfNeeded更新：

self.horizontalConstraint.constant += 10 // move right 10 px.
UIView.animateWithDuration(0.5) {
    self.view.layoutIfNeeded()
}