更改链式动画中的 UIView 约束

Question

我正在尝试创建 UIButton 的链接动画，两个动画之间有延迟：

    let firstAnimation: TimeInterval = 0.3
    let secondAnimation: TimeInterval = 0.35
    let delay: TimeInterval = 2.0
    let animationDuration: TimeInterval = firstAnimation + secondAnimation + delay

    UIView.animateKeyframes(withDuration: animationDuration, delay: 0, options: [], animations: {
        UIView.addKeyframe(withRelativeStartTime: 0, relativeDuration: firstAnimation / animationDuration, animations: {
            self.enterEqualWidthConstraint.isActive = false
            self.enterWidthConstraint.constant = self.view.frame.width
            self.enterWidthConstraint.isActive = true
            self.enterButton.setTitle("HAVE FUN!", for: .normal)
            print("now1")
            self.view.layoutIfNeeded()
        })

        UIView.addKeyframe(withRelativeStartTime: delay / animationDuration, relativeDuration: secondAnimation / animationDuration, animations: {
            print("now2")
            self.enterWidthConstraint.constant = 0
            self.enterButton.setTitle("ENTER", for: .normal)
            self.view.layoutIfNeeded()
        })
    }, completion: nil)
}

同时打印输出：

now1
now2

和偶self.enterWidthConstraint.constat延迟.

我怎样才能在两个链接的动画之间有延迟？
如果约束在延迟之前更改，UIButton 内的文本将消失。
在这些之后我需要做一些其他的动画，但我被困在第一个。

更新
我尝试了没有关键帧的方法，但是延迟不起作用：

    UIView.animate(withDuration: 0.30, animations: {
        self.enterEqualWidthConstraint.isActive = false
        self.enterWidthConstraint.constant = self.view.frame.width
        self.enterWidthConstraint.isActive = true
        self.enterButton.setTitle("HAVE FUN!", for: .normal)
        print("now1")
        self.view.layoutIfNeeded()
    }, completion: { _ in
        UIView.animate(withDuration: 0.35, delay: 2.0, options: [], animations: {
            print("now2")
            self.enterButton.setTitle("ENTER", for: .normal)
            self.enterWidthConstraint.constant = 0
            self.view.layoutIfNeeded()
        }, completion: nil)
    })

它做同样的事情。

Answer 1

UIView.animate(withDuration: 0.30, animations: {
        self.enterEqualWidthConstraint.isActive = false
        self.enterWidthConstraint.constant = self.view.frame.width
        self.enterWidthConstraint.isActive = true
        self.enterButton.setTitle("HAVE FUN!", for: .normal)
        print("now1")
        self.view.layoutIfNeeded()
    }, completion: { _ in

        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{

              self.enterButton.setTitle("ENTER", for: .normal)

              UIView.animate(withDuration: 0.35, animations: {

                     print("now2")
                     self.enterWidthConstraint.constant = 0
                     self.view.layoutIfNeeded()
             }, completion: nil)
        })
});

另一种方法是启动两个独立的动画而不是链接它

 UIView.animate(withDuration: 0.30, animations: {
            self.enterEqualWidthConstraint.isActive = false
            self.enterWidthConstraint.constant = self.view.frame.width
            self.enterWidthConstraint.isActive = true
            self.enterButton.setTitle("HAVE FUN!", for: .normal)
            print("now1")
            self.view.layoutIfNeeded()
        }, completion: { _ in             
                  self.enterButton.setTitle("ENTER", for: .normal)
   });

    UIView.animate(withDuration: 0.35, delay: 2.0, options: [], animations: {
        print("now2")
        self.enterWidthConstraint.constant = 0
        self.view.layoutIfNeeded()
    }, completion: nil)

更改链式动画中的 UIView 约束

Change UIView constraints in chained animations

animation

constraints

chained

ios

swift