[英]Swift: restoring UIView center after moving it
我正在使用手勢縮放和移動UIImageView(例如,Instagram縮放)。 手勢結束后,我想恢復UIImageView的初始位置,但是由於它是參考類型,所以無法獲得初始中心的副本。 使用:
let prevCenter = myImage.center
當然是沒用的。 我該如何復制?
縮放並移動時,將transform
應用於視圖。 最后,只需設置.identity
值即可。
編輯
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
}
您確定沒有在prevCenter
地方更新prevCenter
嗎? center
是struct,因此復制它應該沒有問題。
只需在視圖處於原始狀態時,開始縮放之前以及在使用正確的框架繪制視圖后確保將其(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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