使用 swift 在屏幕上拖动图像

Question

这个方法我试过了

@IBAction func handlePan(recognizer:UIPanGestureRecognizer) {

 let translation = recognizer.translationInView(self.view)
 if let view = recognizer.view {
  view.center = CGPoint(x:view.center.x + translation.x,
                        y:view.center.y + translation.y)
}
 recognizer.setTranslation(CGPointZero, inView: self.view)
}

它正在工作，但问题是当我在多个图像上使用此方法时会产生一些问题，例如， 当拖动一个图像并更改其位置但当我单击并拖动第二个图像时。我的第一张图片回到原来的位置。 以下是我从滚动视图中获得的图像： 当我点击第二张图片时，第一张图片也转到原来的位置

我在这里拖动图像很好

Answer 1

class DraggableImageView: UIImageView {


var dragStartPositionRelativeToCenter : CGPoint?

override init(image: UIImage!) {
    super.init(image: image)

    self.userInteractionEnabled = true   //< w00000t!!!1

    addGestureRecognizer(UIPanGestureRecognizer(target: self, action: "handlePan:"))

    layer.shadowColor = UIColor.blackColor().CGColor
    layer.shadowOffset = CGSize(width: 0, height: 3)
    layer.shadowOpacity = 0.5
    layer.shadowRadius = 2
}

required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
}

func handlePan(nizer: UIPanGestureRecognizer!) {
    if nizer.state == UIGestureRecognizerState.Began {
        let locationInView = nizer.locationInView(superview)
        dragStartPositionRelativeToCenter = CGPoint(x: locationInView.x - center.x, y: locationInView.y - center.y)

        layer.shadowOffset = CGSize(width: 0, height: 20)
        layer.shadowOpacity = 0.3
        layer.shadowRadius = 6

        return
    }

    if nizer.state == UIGestureRecognizerState.Ended {
        dragStartPositionRelativeToCenter = nil

        layer.shadowOffset = CGSize(width: 0, height: 3)
        layer.shadowOpacity = 0.5
        layer.shadowRadius = 2

        return
    }

    let locationInView = nizer.locationInView(superview)

    UIView.animateWithDuration(0.1) {
        self.center = CGPoint(x: locationInView.x - self.dragStartPositionRelativeToCenter!.x,
            y: locationInView.y - self.dragStartPositionRelativeToCenter!.y)
    }
}

/*
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
override func drawRect(rect: CGRect) {
// Drawing code
}
*/   
}

Answer 2

Auto Layout 正在运行将您的图像放回约束要求的位置。

解决此问题的最简单方法是在代码中创建图像，而不是在情节提要中创建它们。

类似：

let lightBulb = UIImageView(frame: CGRectMake(100, 100, 50, 50))
lightBulb.image = UIImage(named: "lightBulb")
lightBulb.contentMode = .ScaleToFill
lightBulb.userInteractionEnabled = true

lightBulb.addGestureRecognizer(UIPanGestureRecognizer(target: self, action: "handlePan:"))

self.view.addSubview(lightBulb)

Answer 3

Swift 4 及以上

在 viewDidLoad() 中设置手势并添加以下方法：

override func viewDidLoad() {
    let panGesture = UIPanGestureRecognizer(target: self, action: #selector(self.panGesture))
    yourView.addGestureRecognizer(panGesture)
}

@objc func panGesture(sender: UIPanGestureRecognizer) {
    var relativePosition: CGPoint?
    if sender.state == UIGestureRecognizer.State.began {
        let locationInView = sender.location(in: super.view)
        relativePosition = CGPoint(x: locationInView.x - (sender.view?.center.x ?? 0.0), y: locationInView.y - (sender.view?.center.y ?? 0.0))
        return
    }
    if sender.state == UIGestureRecognizer.State.ended {
        relativePosition = nil
        return
    }
    let locationInView = sender.location(in: super.view)
    guard let pos = relativePosition else {
        return
    }
    sender.view?.center = CGPoint(x: locationInView.x - pos.x,
                                  y: locationInView.y - pos.y)
}