ios - CGAffine 使用 UIPanGestureRecognizer 转换 UIView

Question

我有 View A，在自身 View 上添加 subview 。我想当我在 View A 上绘制 panGestureRegonizer 时， View A 将跟随绘制移动。

并且在移动 View A 时会缩放。当 View 移动到屏幕的顶部/左侧/底部/右侧时， View A 将缩放到更小，当 View 移动到屏幕中心时， View 会缩放到更大。

我尝试了很多解决方案，但我做不到。

请建议帮助我？

Answer 1

逻辑:您有坐标系(CS)，中心为 x 和 y。当用户使用平移手势时，他/她在 CS 中生成点序列。所以我们的任务是测量CS中心和用户点之间的距离。当我们有最远的距离时，我们可以计算缩放 View 的比例因子。

var center: CGPoint! //center of the CS
let maxSize: CGSize = CGSize.init(width: 100, height: 100) // maximum size of our scaling view
var maxLengthToCenter: CGFloat! //maximum distance from the center of the CS to the furthest point in the CS

private func prepareForScaling() {
    self.center = self.view.center //we set the center of our CS to equal the center of the VC's view
    let frame = self.view.frame
    //the furthest distance in the CS is the diagonal, and we calculate it using pythagoras theorem
    self.maxLengthToCenter = (frame.width*frame.width + frame.height*frame.height).squareRoot() 
}

然后我们需要调用我们的设置函数来让我们的数据为缩放功能做好准备——我们可以在 viewDidLoad 中执行此操作:

override func viewDidLoad() {
    super.viewDidLoad()  
    self.prepareForScaling()
}

然后我们需要一个辅助函数来计算我们 View 的缩放大小，用于用户平移手势在屏幕上的当前位置。

private func scaledSize(for location: CGPoint) -> CGSize {
    //calculate location x,y differences from the center
    let xDifference = location.x - self.center.x
    let yDifference = location.y - self.center.y

    //calculate the scale factor - note that this factor will be between 0.0(center) and 0.5(diagonal - furthest point)    
    //It is due our measurement - from center to view's edge. Consider multiplying this factor with your custom constant.
    let scaleFactor = (xDifference*xDifference + yDifference*yDifference).squareRoot()/maxLengthToCenter
    //create scaled size with maxSize and current scale factor
    let scaledSize = CGSize.init(width: maxSize.width*(1-scaleFactor), height: maxSize.height*(1-scaleFactor))

    return scaledSize
}

最后，我们需要修改平移手势 Action 来改变 A 的大小:

@IBAction func panGestureAction(_ sender: UIPanGestureRecognizer) {
    UIView.animateKeyframes(withDuration: 0.1, delay: 0, options: UIViewKeyframeAnimationOptions.calculationModeLinear, animations: {

        let location = sender.location(in: sender.view?.superview)

        sender.view?.frame = CGRect.init(origin: CGPoint.init(x: 0, y: 0), size: self.scaledSize(for: location))

        sender.view?.center = location
    })
}