我有一个函数，每次按下按钮都会向主视图添加一个新的UIView。我希望这些视图中的每一个都是可拖动的。目前，我正在为每个视图添加一个平移手势识别器，它可以更改每个视图的布局约束。
我的问题是，在移动每个视图之前，我没有正确禁用它的原始约束，所以新旧约束会发生冲突。
这是我的代码：
import UIKit
class ViewController5: UIViewController, UINavigationControllerDelegate, UIGestureRecognizerDelegate {
var textPosXConstraint = NSLayoutConstraint()
var textPosYConstraint = NSLayoutConstraint()
var numberOfViews = 0
var startingConstantPosX: CGFloat = 0.0
var startingConstantPosY: CGFloat = 100.0
override func viewDidLoad() {
super.viewDidLoad()
navigationItem.title = "edit views"
navigationItem.rightBarButtonItem = UIBarButtonItem(title: "add", style: .plain, target: self, action: #selector(addView))
navigationItem.leftBarButtonItem = UIBarButtonItem(title: "Clear", style: .plain, target: self, action: #selector(clearThis))
}
@objc func addView() {
let view1 = UIView()
view1.backgroundColor = UIColor.yellow
view1.frame = CGRect()
view.addSubview(view1)
view1.translatesAutoresizingMaskIntoConstraints = false
view1.widthAnchor.constraint(equalToConstant: 80).isActive = true
view1.heightAnchor.constraint(equalToConstant: 80).isActive = true
textPosXConstraint = view1.centerXAnchor.constraint(equalTo: view.centerXAnchor, constant: 0)
textPosXConstraint.isActive = true
textPosYConstraint = view1.centerYAnchor.constraint(equalTo: view.topAnchor, constant: 100)
textPosYConstraint.isActive = true
numberOfViews+=1
view1.tag = numberOfViews
//add pan gesture
let panGestureRecognizer = UIPanGestureRecognizer(target: self, action: #selector(handlePan))
panGestureRecognizer.delegate = self
view1.addGestureRecognizer(panGestureRecognizer)
}
@objc func clearThis() {
for view in view.subviews {
view.removeFromSuperview()
}
numberOfViews = 0
}
@objc func handlePan(_ gestureRecognizer: UIPanGestureRecognizer) {
guard let currentView = gestureRecognizer.view else { return }
if gestureRecognizer.state == .began {
print("view being moved is: (currentView.tag)")
startingConstantPosY = textPosYConstraint.constant
startingConstantPosX = textPosXConstraint.constant
} else if gestureRecognizer.state == .changed {
let translation = gestureRecognizer.translation(in: self.view)
let newXConstant = self.startingConstantPosX + translation.x
let newYConstant = self.startingConstantPosY + translation.y
currentView.centerXAnchor.constraint(equalTo: view.centerXAnchor, constant: startingConstantPosX).isActive = false
currentView.centerXAnchor.constraint(equalTo: view.centerXAnchor, constant: newXConstant).isActive = true
}
}
}
理想情况下，它可以工作，这样用户就可以添加他们想要的任意多的视图，并移动每个视图。
谢谢你的帮助！
您需要保留对为视图创建的位置约束的引用，以便在创建新约束之前更改其constant值或设置isActive = false。
- 创建一个名为
MovableView的UIView子类，该子类具有horizontalConstraint和verticalConstraint的NSLayoutConstraint?属性 - 在设置约束的
isActive = true之前，在创建约束时设置这些特性 -
当需要移动
MovableView时，请更新horizontalConstraint和verticalConstraint的constant属性。moveableView.horizontalConstraint?.constant = newXConstant moveableView.verticalConstraint?.constant = newYConstant或者，可以在创建、指定和激活新约束之前设置
horizontalConstraint?.isActive = false和verticalConstraint?.isActive = false。moveableView.horizontalConstraint?.isActive = false moveableView.verticalConstraint?.isActive = false moveableView.horizontalConstraint = ... moveableView.horizontalConstraint?.isActive = true moveableView.verticalConstraint = ... moveableView.verticalConstraint?.isActive = true
有关我4年前写的可拖动视图的实现，请参阅可拖动视图。它已经过时，需要更新，但你可能会从中得到一些想法。还可以阅读下面的评论，@Matt解释说，你可以跳过对可拖动视图的限制。可以向屏幕添加不参与自动布局的视图，即使屏幕的其他部分参与。
我修复了你的代码：
- 您没有提供
MovableView的实现，但约束属性似乎是static，而不是成员属性。您需要将它们作为成员属性，以便支持多个可移动视图 - 您交换了
startingConstantPosX和startingConstantPosY，这就是导致跳跃的原因
class MovableView: UIView {
var horizontalConstraint: NSLayoutConstraint?
var verticalConstraint: NSLayoutConstraint?
}
class ViewController: UIViewController, UINavigationControllerDelegate, UIGestureRecognizerDelegate {
var numberOfViews = 0
var startingConstantPosX: CGFloat = 0.0
var startingConstantPosY: CGFloat = 100.0
override func viewDidLoad() {
super.viewDidLoad()
navigationItem.title = "edit views"
navigationItem.rightBarButtonItem = UIBarButtonItem(title: "add", style: .plain, target: self, action: #selector(addView))
navigationItem.leftBarButtonItem = UIBarButtonItem(title: "Clear", style: .plain, target: self, action: #selector(clearThis))
}
@objc func addView() {
let view1 = MovableView()
view1.backgroundColor = UIColor.yellow
view1.frame = CGRect()
view.addSubview(view1)
view1.translatesAutoresizingMaskIntoConstraints = false
view1.widthAnchor.constraint(equalToConstant: 80).isActive = true
view1.heightAnchor.constraint(equalToConstant: 80).isActive = true
view1.horizontalConstraint = view1.centerXAnchor.constraint(equalTo: view.centerXAnchor, constant: 0)
view1.horizontalConstraint?.isActive = true
view1.verticalConstraint = view1.centerYAnchor.constraint(equalTo: view.topAnchor, constant: 100)
view1.verticalConstraint?.isActive = true
numberOfViews+=1
view1.tag = numberOfViews
//add pan gesture
let panGestureRecognizer = UIPanGestureRecognizer(target: self, action: #selector(handlePan))
panGestureRecognizer.delegate = self
view1.addGestureRecognizer(panGestureRecognizer)
}
@objc func clearThis() {
for view in view.subviews {
view.removeFromSuperview()
}
numberOfViews = 0
}
@objc func handlePan(_ gestureRecognizer: UIPanGestureRecognizer) {
guard let currentView = gestureRecognizer.view as? MovableView else { return }
if gestureRecognizer.state == .began {
print("view being moved is: (currentView.tag)")
startingConstantPosX = currentView.horizontalConstraint?.constant ?? 0
startingConstantPosY = currentView.verticalConstraint?.constant ?? 0
} else if gestureRecognizer.state == .changed {
let translation = gestureRecognizer.translation(in: self.view)
let newXConstant = startingConstantPosX + translation.x
let newYConstant = startingConstantPosY + translation.y
currentView.horizontalConstraint?.constant = newXConstant
currentView.verticalConstraint?.constant = newYConstant
}
}
}
如果每次调用handlePan时都将translation设置回.zero，则无需跟踪起始位置即可简化代码：
@objc func handlePan(_ gestureRecognizer: UIPanGestureRecognizer) {
guard let currentView = gestureRecognizer.view as? MovableView else { return }
if gestureRecognizer.state == .began {
print("view being moved is: (currentView.tag)")
} else if gestureRecognizer.state == .changed {
let translation = gestureRecognizer.translation(in: self.view)
currentView.horizontalConstraint?.constant += translation.x
currentView.verticalConstraint?.constant += translation.y
gestureRecognizer.setTranslation(.zero, in: self.view)
}
}