步骤1：选择一个视图，将其拖到故事板中。

@IBOutlet weak var viewDrag: UIView!

**步骤2：**添加PanGesture。

var panGesture       = UIPanGestureRecognizer()

**步骤3：**在ViewDidLoad中添加以下代码。

override func viewDidLoad() {
    super.viewDidLoad()

    panGesture = UIPanGestureRecognizer(target: self, action: #selector(ViewController.draggedView(_:)))
    viewDrag.isUserInteractionEnabled = true
    viewDrag.addGestureRecognizer(panGesture)

}

**步骤4：**draggedView的代码。

func draggedView(_ sender:UIPanGestureRecognizer){
    self.view.bringSubview(toFront: viewDrag)
    let translation = sender.translation(in: self.view)
    viewDrag.center = CGPoint(x: viewDrag.center.x + translation.x, y: viewDrag.center.y + translation.y)
    sender.setTranslation(CGPoint.zero, in: self.view)
}

**步骤5：**输出。

一月一日

• • 第1步：从情节提要中选取一个UIView，将其拖动到ViewController文件中并创建UIView的IBOutlet。**

@IBOutlet weak var viewDrag: UIView!
var panGesture = UIPanGestureRecognizer()

• • 步骤2：在viewDidLoad（）中添加以下代码。**

override func viewDidLoad() {
super.viewDidLoad()
  let panGesture = UIPanGestureRecognizer(target: self, action:(Selector(("draggedView:"))))
  viewDrag.isUserInteractionEnabled = true
  viewDrag.addGestureRecognizer(panGesture)
}

• • 第3步：创建func并添加代码来移动UIView，如下所示。**

func draggedView(sender:UIPanGestureRecognizer){
    self.view.bringSubviewToFront(viewDrag)
    let translation = sender.translation(in: self.view)
    viewDrag.center = CGPoint(x: viewDrag.center.x + translation.x, y: viewDrag.center.y + translation.y)
    sender.setTranslation(CGPoint.zero, in: self.view)
}

希望这能对人有所帮助。

如果你子类化一个视图，这是非常容易的：

可拖动视图...

class DraggableView: UIIView {
    
    var fromleft: NSLayoutConstraint!
    var fromtop: NSLayoutConstraint!
    
    override func didMoveToWindow() {
        super.didMoveToWindow()
        if window != nil {
            fromleft = constraint(id: "fromleft")!
            fromtop = constraint(id: "fromtop")!
        }
    }
    
    override func common() {
        super.common()
        let p = UIPanGestureRecognizer(
           target: self, action: #selector(drag))
        addGestureRecognizer(p)
    }
    
    @objc func drag(_ s:UIPanGestureRecognizer) {
        let t = s.translation(in: self.superview)
        fromleft.constant = fromleft.constant + t.x
        fromtop.constant = fromtop.constant + t.y
        s.setTranslation(CGPoint.zero, in: self.superview)
    }
}

1.将UIView拖放到场景中。
1.通常，从左侧（即x位置）添加约束，从顶部（即y位置）添加约束。
1.在故事板中，只需简单地命名约束"fromleft"和"fromtop"

你完了。
它现在工作得很好-就是这样。

那个方便的constraint(调用是什么？

请注意，视图只是通过名称找到自己的约束。
在Xcode中，仍然没有办法使用IBOutlets这样的约束。幸运的是，通过"标识符"找到它们非常容易。（事实上，这正是.identifier特性在约束上的用途。）

extension UIView {
    
    func constraint(id: String) -> NSLayoutConstraint? {
        let cc = self.allConstraints()
        for c in cc { if c.identifier == id { return c } }
        //print("someone forgot to label constraint \(id)") //heh!
        return nil
    }
    
    func allConstraints() -> [NSLayoutConstraint] {
        var views = [self]
        var view = self
        while let superview = view.superview {
            views.append(superview)
            view = superview
        }
        return views.flatMap({ $0.constraints }).filter { c in
            return c.firstItem as? UIView == self ||
                c.secondItem as? UIView == self
        }
    }

尖端...边缘对中心!

不要忘记在视图上设置约束（如上图所示）：
您可以将左边的设置为：

• 到白框的"左边缘"，或
• 到白色盒子的"中心"。

根据你的情况选择一个合适的。它会让你更容易计算，设置滑块等。
脚注-"初始化" UI视图、UI "I"视图、

// UI "I" View ... "I" for initializing
// Simply saves you typing inits everywhere
import UIKit
class UIIView: UIView {
    override init(frame: CGRect) {
        super.init(frame: frame)
        common()
    }
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        common()
    }
    func common() { }
}

此UIView扩展使UIView对象可拖动，并将移动限制在屏幕范围内。

extension UIView {
    func makeDraggable() {
        let panGesture = UIPanGestureRecognizer(target: self, action: #selector(handlePan(_:)))
        self.addGestureRecognizer(panGesture)
    }
    
    @objc func handlePan(_ gesture: UIPanGestureRecognizer) {
        guard gesture.view != nil else { return }
        
        let translation = gesture.translation(in: gesture.view?.superview)
        
        var newX = gesture.view!.center.x + translation.x
        var newY = gesture.view!.center.y + translation.y
        
        let halfWidth = gesture.view!.bounds.width / 2.0
        let halfHeight = gesture.view!.bounds.height / 2.0
        
        // Limit the movement to stay within the bounds of the screen
        newX = max(halfWidth, newX)
        newX = min(UIScreen.main.bounds.width - halfWidth, newX)
        newY = max(halfHeight, newY)
        newY = min(UIScreen.main.bounds.height - halfHeight, newY)
        
        gesture.view?.center = CGPoint(x: newX, y: newY)
        gesture.setTranslation(CGPoint.zero, in: gesture.view?.superview)
    }
}