尝试在swift中设置约束动画

问题描述 投票：207回答：6

我有一个UITextField，我想在点击时放大它的宽度。我设置了约束，并确保左边的约束优先级低于我试图在右边设置动画的约束。

这是我尝试使用的代码。

  // move the input box
    UIView.animateWithDuration(10.5, animations: {
        self.nameInputConstraint.constant = 8
        }, completion: {
            (value: Bool) in
            println(">>> move const")
    })

这有效，但它似乎只是瞬间发生，似乎没有任何动作。我试着设置它10秒钟以确保我没有遗漏任何东西，但我得到了相同的结果。

nameInputConstraint是我控制拖动以从IB连接到我的类的约束的名称。

感谢您的帮助！

xcode swift constraints xcode6
6个回答
591
投票

您需要先更改约束，然后为更新设置动画。

self.nameInputConstraint.constant = 8

斯威夫特2

UIView.animateWithDuration(0.5) {
    self.view.layoutIfNeeded()
}

斯威夫特3,4,5

UIView.animate(withDuration: 0.5) {
    self.view.layoutIfNeeded()
}
19
投票

SWIFT 4.x：

self.mConstraint.constant = 100.0
UIView.animate(withDuration: 0.3) {
        self.view.layoutIfNeeded()
}

完成示例：

self.mConstraint.constant = 100
UIView.animate(withDuration: 0.3, animations: {
        self.view.layoutIfNeeded()
    }, completion: {res in
        //Do something
})
9
投票

指出view.layoutIfNeeded()仅适用于视图子视图非常重要。

因此，要为视图约束设置动画，在视图到动画的超视图上调用它非常重要，如下所示：

    topConstraint.constant = heightShift

    UIView.animate(withDuration: 0.3) {

        // request layout on the *superview*
        self.view.superview?.layoutIfNeeded()
    }

简单布局的示例如下：

class MyClass {

    /// Container view
    let container = UIView()
        /// View attached to container
        let view = UIView()

    /// Top constraint to animate
    var topConstraint = NSLayoutConstraint()


    /// Create the UI hierarchy and constraints
    func createUI() {
        container.addSubview(view)

        // Create the top constraint
        topConstraint = view.topAnchor.constraint(equalTo: container.topAnchor, constant: 0)


        view.translatesAutoresizingMaskIntoConstraints = false

        // Activate constaint(s)
        NSLayoutConstraint.activate([
           topConstraint,
        ])
    }

    /// Update view constraint with animation
    func updateConstraint(heightShift: CGFloat) {
        topConstraint.constant = heightShift

        UIView.animate(withDuration: 0.3) {

            // request layout on the *superview*
            self.view.superview?.layoutIfNeeded()
        }
    }
}
7
投票

使用Swift 5和iOS 12.3，根据您的需要，您可以选择以下3种方法之一来解决您的问题。

＃1。使用UIView的animate(withDuration:animations:)类方法

animate(withDuration:animations:)有以下声明：

使用指定的持续时间对一个或多个视图进行动画更改。

class func animate(withDuration duration: TimeInterval, animations: @escaping () -> Void)

下面的Playground代码显示了animate(withDuration:animations:)的可能实现，以便为Auto Layout约束的常量更改设置动画。

import UIKit
import PlaygroundSupport

class ViewController: UIViewController {

    let textView = UITextView()
    lazy var heightConstraint = textView.heightAnchor.constraint(equalToConstant: 50)

    override func viewDidLoad() {
        view.backgroundColor = .white
        view.addSubview(textView)

        textView.backgroundColor = .orange
        textView.isEditable = false
        textView.text = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum."

        textView.translatesAutoresizingMaskIntoConstraints = false
        textView.topAnchor.constraint(equalToSystemSpacingBelow: view.layoutMarginsGuide.topAnchor, multiplier: 1).isActive = true
        textView.leadingAnchor.constraint(equalTo: view.layoutMarginsGuide.leadingAnchor).isActive = true
        textView.trailingAnchor.constraint(equalTo: view.layoutMarginsGuide.trailingAnchor).isActive = true
        heightConstraint.isActive = true

        let tapGesture = UITapGestureRecognizer(target: self, action: #selector(doIt(_:)))
        textView.addGestureRecognizer(tapGesture)
    }

    @objc func doIt(_ sender: UITapGestureRecognizer) {
        heightConstraint.constant = heightConstraint.constant == 50 ? 150 : 50
        UIView.animate(withDuration: 2) {
            self.view.layoutIfNeeded()
        }
    }

}

PlaygroundPage.current.liveView = ViewController()

＃2。使用UIViewPropertyAnimator的init(duration:curve:animations:)初始化器和startAnimation()方法

init(duration:curve:animations:)有以下声明：

使用内置的UIKit时序曲线初始化动画师。

convenience init(duration: TimeInterval, curve: UIViewAnimationCurve, animations: (() -> Void)? = nil)

下面的Playground代码显示了init(duration:curve:animations:)和startAnimation()的可能实现，以便为Auto Layout约束的常量更改设置动画。

import UIKit
import PlaygroundSupport

class ViewController: UIViewController {

    let textView = UITextView()
    lazy var heightConstraint = textView.heightAnchor.constraint(equalToConstant: 50)

    override func viewDidLoad() {
        view.backgroundColor = .white
        view.addSubview(textView)

        textView.backgroundColor = .orange
        textView.isEditable = false
        textView.text = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum."

        textView.translatesAutoresizingMaskIntoConstraints = false
        textView.topAnchor.constraint(equalToSystemSpacingBelow: view.layoutMarginsGuide.topAnchor, multiplier: 1).isActive = true
        textView.leadingAnchor.constraint(equalTo: view.layoutMarginsGuide.leadingAnchor).isActive = true
        textView.trailingAnchor.constraint(equalTo: view.layoutMarginsGuide.trailingAnchor).isActive = true
        heightConstraint.isActive = true

        let tapGesture = UITapGestureRecognizer(target: self, action: #selector(doIt(_:)))
        textView.addGestureRecognizer(tapGesture)
    }

    @objc func doIt(_ sender: UITapGestureRecognizer) {
        heightConstraint.constant = heightConstraint.constant == 50 ? 150 : 50
        let animator = UIViewPropertyAnimator(duration: 2, curve: .linear, animations: {
            self.view.layoutIfNeeded()
        })
        animator.startAnimation()
    }

}

PlaygroundPage.current.liveView = ViewController()

＃3。使用UIViewPropertyAnimator的runningPropertyAnimator(withDuration:delay:options:animations:completion:)类方法

runningPropertyAnimator(withDuration:delay:options:animations:completion:)有以下声明：

创建并返回一个动画对象，该对象立即开始运行其动画。

class func runningPropertyAnimator(withDuration duration: TimeInterval, delay: TimeInterval, options: UIViewAnimationOptions = [], animations: @escaping () -> Void, completion: ((UIViewAnimatingPosition) -> Void)? = nil) -> Self

下面的Playground代码显示了runningPropertyAnimator(withDuration:delay:options:animations:completion:)的可能实现，以便为Auto Layout约束的常量更改设置动画。

import UIKit
import PlaygroundSupport

class ViewController: UIViewController {

    let textView = UITextView()
    lazy var heightConstraint = textView.heightAnchor.constraint(equalToConstant: 50)

    override func viewDidLoad() {
        view.backgroundColor = .white
        view.addSubview(textView)

        textView.backgroundColor = .orange
        textView.isEditable = false
        textView.text = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum."

        textView.translatesAutoresizingMaskIntoConstraints = false
        textView.topAnchor.constraint(equalToSystemSpacingBelow: view.layoutMarginsGuide.topAnchor, multiplier: 1).isActive = true
        textView.leadingAnchor.constraint(equalTo: view.layoutMarginsGuide.leadingAnchor).isActive = true
        textView.trailingAnchor.constraint(equalTo: view.layoutMarginsGuide.trailingAnchor).isActive = true
        heightConstraint.isActive = true

        let tapGesture = UITapGestureRecognizer(target: self, action: #selector(doIt(_:)))
        textView.addGestureRecognizer(tapGesture)
    }

    @objc func doIt(_ sender: UITapGestureRecognizer) {
        heightConstraint.constant = heightConstraint.constant == 50 ? 150 : 50
        UIViewPropertyAnimator.runningPropertyAnimator(withDuration: 2, delay: 0, options: [], animations: {
            self.view.layoutIfNeeded()
        })
    }

}

PlaygroundPage.current.liveView = ViewController()
3
投票

就我而言，我只更新了自定义视图。

// DO NOT LIKE THIS
customView.layoutIfNeeded()    // Change to view.layoutIfNeeded()
UIView.animate(withDuration: 0.5) {
   customViewConstraint.constant = 100.0
   customView.layoutIfNeeded() // Change to view.layoutIfNeeded()
}
-1
投票

看看this。

视频说你需要像下面这样添加self.view.layoutIfNeeded()：

UIView.animate(withDuration: 1.0, animations: {
       self.centerX.constant -= 75
       self.view.layoutIfNeeded()
}, completion: nil)
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