ios - 通过滑动更改自动布局限制
问题描述
屏幕上有两张图片,它们是以编程方式设置的限制。在向左滑动时,图片会改变大小并变成应有的样子。如果在那之后,向右滑动,那么什么都不会发生,图片会留在原处。这是实现代码。
func Swipe() {
let swipeLeft = UISwipeGestureRecognizer(target: self, action: #selector(handleGesture))
swipeLeft.direction = .left
self.view.addGestureRecognizer(swipeLeft)
let swipeRight = UISwipeGestureRecognizer(target: self, action: #selector(handleGesture))
swipeRight.direction = .right
self.view.addGestureRecognizer(swipeRight)
}
@objc func handleGesture(gesture: UISwipeGestureRecognizer) -> Void {
if gesture.direction == .right {
UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 1, initialSpringVelocity: 1, options: .curveEaseOut, animations:{
self.setupLayoutImageOne()
}, completion: nil)
self.view.layoutIfNeeded()
} else if gesture.direction == .left {
UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 1, initialSpringVelocity: 1, options: .curveEaseOut, animations:{
self.setupLayoutImageTwo()
}, completion: nil)
self.view.layoutIfNeeded()
}
}
func setupLayoutImageOne()
{
imageOne.translatesAutoresizingMaskIntoConstraints = false
imageTwo.translatesAutoresizingMaskIntoConstraints = false
let layoutGuide = view
NSLayoutConstraint.activate([
imageOne.topAnchor.constraint(equalTo: layoutGuide!.topAnchor),
imageOne.leadingAnchor.constraint(equalTo: layoutGuide!.leadingAnchor),
imageOne.trailingAnchor.constraint(equalTo: layoutGuide!.trailingAnchor,constant: 170) ,
imageOne.bottomAnchor.constraint(equalTo: layoutGuide!.bottomAnchor,constant: 290),
imageTwo.bottomAnchor.constraint(equalTo: layoutGuide!.bottomAnchor,constant: 530),
imageTwo.leadingAnchor.constraint(equalTo: layoutGuide!.leadingAnchor,constant: 200),
imageTwo.trailingAnchor.constraint(equalTo: layoutGuide!.trailingAnchor,constant: 200),
imageTwo.topAnchor.constraint(equalTo: layoutGuide!.topAnchor,constant: 800),
])
}
func setupLayoutImageTwo()
{
imageOne.translatesAutoresizingMaskIntoConstraints = false
imageTwo.translatesAutoresizingMaskIntoConstraints = false
let layoutGuide = view
NSLayoutConstraint.activate([
imageOne.topAnchor.constraint(equalTo: layoutGuide!.topAnchor),
imageOne.leadingAnchor.constraint(equalTo: layoutGuide!.leadingAnchor),
imageOne.trailingAnchor.constraint(equalTo: layoutGuide!.trailingAnchor,constant: 299) ,
imageOne.bottomAnchor.constraint(equalTo: layoutGuide!.bottomAnchor,constant: 570),
imageTwo.bottomAnchor.constraint(equalTo: layoutGuide!.bottomAnchor),
imageTwo.leadingAnchor.constraint(equalTo: layoutGuide!.leadingAnchor),
imageTwo.trailingAnchor.constraint(equalTo: layoutGuide!.trailingAnchor),
imageTwo.topAnchor.constraint(equalTo: layoutGuide!.topAnchor),
])
}
当我向右滑动时,它会给出这样的错误
将尝试通过打破约束来恢复(活动,名称:'|':UIView:0x10080e7a0)>
在 UIViewAlertForUnsatisfiableConstraints 创建一个符号断点以在调试器中捕获它。中列出的 UIView 上的 UIConstraintBasedLayoutDebugging 类别中的方法也可能会有所帮助。致命错误:在隐式展开可选值时意外发现 nil 2020-01-28 15:09:59.920450+0200 ThemeGame[27748:2857822] 致命错误:在隐式展开可选值时意外发现 nil
解决方案
由于您已经发布了几个非常相似的问题,我强烈建议您花一些时间了解约束和自动布局的工作原理。
imageView 框架看起来很奇怪,因为这条线(例如):
imageOne.bottomAnchor.constraint(equalTo: layoutGuide!.bottomAnchor,constant: 290)
将 imageView 的底部放置在视图底部下方290 点处,因此 290 点(像素)将“离屏”。
但是,这是基于您发布的代码的一种方法。我们为每个 imageView 定义其“向左滑动”位置/大小和“向右滑动”位置/大小的约束。我们将这些约束存储在数组中,然后我们可以根据需要激活/停用:
class SwipeViewController: UIViewController {
let imageOne: UIImageView = {
let v = UIImageView()
v.backgroundColor = .red
return v
}()
let imageTwo: UIImageView = {
let v = UIImageView()
v.backgroundColor = .green
return v
}()
// imageOne constraints when swiping Left
var imageOneLeftConstraints: [NSLayoutConstraint] = [NSLayoutConstraint]()
// imageOne constraints when swiping Right
var imageOneRightConstraints: [NSLayoutConstraint] = [NSLayoutConstraint]()
// imageTwo constraints when swiping Left
var imageTwoLeftConstraints: [NSLayoutConstraint] = [NSLayoutConstraint]()
// imageTwo constraints when swiping Right
var imageTwoRightConstraints: [NSLayoutConstraint] = [NSLayoutConstraint]()
override func viewDidLoad() {
super.viewDidLoad()
imageOne.translatesAutoresizingMaskIntoConstraints = false
imageTwo.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(imageOne)
view.addSubview(imageTwo)
guard let layoutGuide = view else { fatalError("this should not fail") }
// local constraint var to reuse
var c: NSLayoutConstraint
// define constraints for imageOne when swiping left
c = imageOne.topAnchor.constraint(equalTo: layoutGuide.topAnchor)
imageOneLeftConstraints.append(c)
c = imageOne.leadingAnchor.constraint(equalTo: layoutGuide.leadingAnchor)
imageOneLeftConstraints.append(c)
c = imageOne.trailingAnchor.constraint(equalTo: layoutGuide.trailingAnchor,constant: 170)
imageOneLeftConstraints.append(c)
c = imageOne.bottomAnchor.constraint(equalTo: layoutGuide.bottomAnchor,constant: 290)
imageOneLeftConstraints.append(c)
// define constraints for imageTwo when swiping left
c = imageTwo.topAnchor.constraint(equalTo: layoutGuide.topAnchor,constant: 800)
imageTwoLeftConstraints.append(c)
c = imageTwo.leadingAnchor.constraint(equalTo: layoutGuide.leadingAnchor,constant: 200)
imageTwoLeftConstraints.append(c)
c = imageTwo.bottomAnchor.constraint(equalTo: layoutGuide.bottomAnchor,constant: 530)
imageTwoLeftConstraints.append(c)
c = imageTwo.trailingAnchor.constraint(equalTo: layoutGuide.trailingAnchor,constant: 200)
imageTwoLeftConstraints.append(c)
// define constraints for imageOne when swiping right
c = imageOne.topAnchor.constraint(equalTo: layoutGuide.topAnchor)
imageOneRightConstraints.append(c)
c = imageOne.leadingAnchor.constraint(equalTo: layoutGuide.leadingAnchor)
imageOneRightConstraints.append(c)
c = imageOne.trailingAnchor.constraint(equalTo: layoutGuide.trailingAnchor,constant: 299)
imageOneRightConstraints.append(c)
c = imageOne.bottomAnchor.constraint(equalTo: layoutGuide.bottomAnchor,constant: 570)
imageOneRightConstraints.append(c)
// define constraints for imageTwo when swiping right
c = imageTwo.topAnchor.constraint(equalTo: layoutGuide.topAnchor)
imageTwoRightConstraints.append(c)
c = imageTwo.leadingAnchor.constraint(equalTo: layoutGuide.leadingAnchor)
imageTwoRightConstraints.append(c)
c = imageTwo.trailingAnchor.constraint(equalTo: layoutGuide.trailingAnchor)
imageTwoRightConstraints.append(c)
c = imageTwo.bottomAnchor.constraint(equalTo: layoutGuide.bottomAnchor)
imageTwoRightConstraints.append(c)
// start with imageViews at "swiped left" positions
NSLayoutConstraint.activate(imageOneLeftConstraints + imageTwoLeftConstraints)
setupSwipe()
}
func setupSwipe() {
let swipeLeft = UISwipeGestureRecognizer(target: self, action: #selector(handleGesture))
swipeLeft.direction = .left
self.view.addGestureRecognizer(swipeLeft)
let swipeRight = UISwipeGestureRecognizer(target: self, action: #selector(handleGesture))
swipeRight.direction = .right
self.view.addGestureRecognizer(swipeRight)
}
@objc func handleGesture(gesture: UISwipeGestureRecognizer) -> Void {
if gesture.direction == .right {
NSLayoutConstraint.deactivate(imageOneLeftConstraints + imageTwoLeftConstraints)
NSLayoutConstraint.activate(imageOneRightConstraints + imageTwoRightConstraints)
UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 1, initialSpringVelocity: 1, options: .curveEaseOut, animations:{
self.view.layoutIfNeeded()
}, completion: nil)
} else if gesture.direction == .left {
NSLayoutConstraint.deactivate(imageOneRightConstraints + imageTwoRightConstraints)
NSLayoutConstraint.activate(imageOneLeftConstraints + imageTwoLeftConstraints)
UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 1, initialSpringVelocity: 1, options: .curveEaseOut, animations:{
self.view.layoutIfNeeded()
}, completion: nil)
}
}
}
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