[英]Swift: restoring UIView center after moving it
我正在使用手势缩放和移动UIImageView(例如,Instagram缩放)。 手势结束后,我想恢复UIImageView的初始位置,但是由于它是参考类型,所以无法获得初始中心的副本。 使用:
let prevCenter = myImage.center
当然是没用的。 我该如何复制?
缩放并移动时,将transform
应用于视图。 最后,只需设置.identity
值即可。
编辑
例:
@IBOutlet weak var butt: UIButton!
var offsetTransform: CGAffineTransform = .identity
var zoomTransform: CGAffineTransform = .identity
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
let pan = UIPanGestureRecognizer(target: self, action: #selector(onPan(pan:)))
pan.minimumNumberOfTouches = 2
pan.delegate = self
view.addGestureRecognizer(pan)
let pinch = UIPinchGestureRecognizer(target: self, action: #selector(onPinch(pinch:)))
pinch.delegate = self
view.addGestureRecognizer(pinch)
}
@objc func onPinch(pinch: UIPinchGestureRecognizer) {
let s = pinch.scale
zoomTransform = CGAffineTransform(scaleX: s, y: s)
butt.transform = offsetTransform.concatenating(zoomTransform)
if (pinch.state == .ended) {
finish()
}
}
@objc func onPan(pan: UIPanGestureRecognizer) {
let t = pan.translation(in: view)
offsetTransform = CGAffineTransform(translationX: t.x, y: t.y)
}
func updatePos() {
butt.transform = offsetTransform.concatenating(zoomTransform)
}
func finish() {
butt.transform = .identity
}
func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
return true
}
您确定没有在prevCenter
地方更新prevCenter
吗? center
是struct,因此复制它应该没有问题。
只需在视图处于原始状态时,开始缩放之前以及在使用正确的框架绘制视图后确保将其(居中)
let imageView = UIImageView(frame: CGRect(x: 10, y: 10, width: 20, height: 20))
let prevCenter = view.center // 20, 20
imageView.center = CGPoint(x: 50, y: 50)
// imageView.center - 50, 50
// prevCenter - 20, 20
imageView.frame = CGRect(x: 40, y: 40, width: 10, height: 10)
// imageView.center - 45, 45
// prevCenter - 20, 20
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