我有一个视图,里面我添加一个标签,然后我尝试使用PanGesture设置移动标签的边界。下面是我的代码:
@objc func handlePan(_ gestureRecognizer: UIPanGestureRecognizer) {
if gestureRecognizer.state == .began || gestureRecognizer.state == .changed {
let translation = gestureRecognizer.translation(in: self)
if let view = gestureRecognizer.view {
if (view.frame.origin.x + translation.x >= 0) && (view.frame.origin.y + translation.y >= 0) && (view.frame.origin.x + translation.x <= view.frame.width) && (view.frame.origin.y + translation.y <= view.frame.height)
{
view.center = CGPoint(x:view.center.x + translation.x,
y:view.center.y + translation.y)
}
}
gestureRecognizer.setTranslation(CGPoint.zero, in: self)
}
}
我参考了这个答案:https://stackoverflow.com/a/49008808/9970928
但是它不起作用,谁能说出我在这种条件下缺少什么?
代码不是最直观的,但假设其他一切正常,问题是它只在右侧和底部超出界限。通过以下方式查看您的状况:
(view.frame.origin.x + translation.x <= view.frame.width)
(view.frame.origin.y + translation.y <= view.frame.height)
所以它说原点可能不大于边界的大小,你要做的是检查内部视图的最大值:
(view.frame.maxX + translation.x <= view.frame.width)
(view.frame.maxY + translation.y <= view.frame.height)
但此过程通常可能会产生问题。想象一下,用户向右快速滑动。并且最大center.x
可能是100
.当前center.x
50
,用户将其拖到单个帧中以200
。您的状况将失败,您的标签将保持在50
而不是100
。我会把框架夹到边界上。
应该执行以下操作:
func clampFrame(_ frame: CGRect, inBounds bounds: CGRect) -> CGRect {
let center: CGPoint = CGPoint(x: max(bounds.minX + frame.width*0.5, min(frame.midX, bounds.maxX - frame.width*0.5)),
y: max(bounds.minY + frame.height*0.5, min(frame.midY, bounds.maxY - frame.height*0.5)))
return CGRect(x: center.x-frame.width*0.5, y: center.y-frame.height*0.5, width: frame.width, height: frame.height)
}
func moveFrame(_ frame: CGRect, by translation: CGPoint, constrainedTo bounds: CGRect) -> CGRect {
var newFrame = frame
newFrame.origin.x += translation.x
newFrame.origin.y += translation.y
return clampFrame(newFrame, inBounds: bounds)
}
使用"翻译"程序可能还有其他问题。我会去找一个位置。请参阅以下工作示例:
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
let myView = MyView(frame: CGRect(x: 100.0, y: 100.0, width: 200.0, height: 200.0))
myView.backgroundColor = UIColor.green
view.addSubview(myView)
let label = UILabel(frame: .zero)
label.backgroundColor = UIColor.blue.withAlphaComponent(0.2)
label.font = UIFont.systemFont(ofSize: 50.0)
label.text = "Hi!"
label.sizeToFit()
myView.addSubview(label)
label.addGestureRecognizer(UIPanGestureRecognizer(target: myView, action: #selector(MyView.handlePan)))
label.isUserInteractionEnabled = true
}
}
class MyView: UIView {
func clampFrame(_ frame: CGRect, inBounds bounds: CGRect) -> CGRect {
let center: CGPoint = CGPoint(x: max(bounds.minX + frame.width*0.5, min(frame.midX, bounds.maxX - frame.width*0.5)),
y: max(bounds.minY + frame.height*0.5, min(frame.midY, bounds.maxY - frame.height*0.5)))
return CGRect(x: center.x-frame.width*0.5, y: center.y-frame.height*0.5, width: frame.width, height: frame.height)
}
func moveFrame(_ frame: CGRect, by translation: CGPoint, constrainedTo bounds: CGRect) -> CGRect {
var newFrame = frame
newFrame.origin.x += translation.x
newFrame.origin.y += translation.y
return clampFrame(newFrame, inBounds: bounds)
}
private var startLocation: CGPoint = .zero
private var startFrame: CGRect = .zero
@objc func handlePan(_ gestureRecognizer: UIPanGestureRecognizer) {
guard let label = gestureRecognizer.view else { return }
if gestureRecognizer.state == .began {
startLocation = gestureRecognizer.location(in: self)
startFrame = label.frame
} else if gestureRecognizer.state == .changed {
let newLocation = gestureRecognizer.location(in: self)
let translation = CGPoint(x: newLocation.x-startLocation.x, y: newLocation.y-startLocation.y)
label.frame = moveFrame(startFrame, by: translation, constrainedTo: self.bounds)
}
}
}