如何为UIView添加大小调整手柄？

首先，我建议为UIView创建一个自定义View子类，您将在此处处理所有行为。我们称它为ResizableView。

在自定义视图中，您需要在角落处为这些点绘制图层或视图并向其添加PangestureRecognized，然后您可以recognizer.locationInView()在用户拖动它们时使用这些点来跟踪这些点的位置，这将用于计算View的比例。您可以参考的代码是：

func rotateViewPanGesture(recognizer: UIPanGestureRecognizer) {
    touchLocation = recognizer.locationInView(self.superview)

    let center = CalculateFunctions.CGRectGetCenter(self.frame)

    switch recognizer.state {
    case .Began:
        initialBounds = self.bounds
        initialDistance = CalculateFunctions.CGpointGetDistance(center, point2: touchLocation!)


    case .Changed:        

        //Finding scale between current touchPoint and previous touchPoint
        let scale = sqrtf(Float(CalculateFunctions.CGpointGetDistance(center, point2: touchLocation!)) / Float(initialDistance!))
        let scaleRect = CalculateFunctions.CGRectScale(initialBounds!, wScale: CGFloat(scale), hScale: CGFloat(scale))

        self.bounds = scaleRect

        self.refresh()

    case:.Ended:
          self.refresh() 

    default:break

一步步

touchLocation location of the Pangesture

center is the center of ResizableView

initialBounds is the initial bounds of the ResizableView when PanGesture begin.

initailDistance is the distance between the center of the ResizableView of touchPoint of the dot the user is dragging.

Then you can calculate the scale given initialDistance, center, touch location

Now you have scaled the view as You want. You also need to refresh the position of these dot at corner accordingly, that's what refresh() for, you need to implement it yourself.

CalculateFunctions

I tend to define some helpFunctions to help me calculate.

CalculateFunctions.CGPointGetDistance is used to calculate the distance between center of the view and touch location.

CalculateFunctions.CGRectScale return the scaled CGRect given the the scale you just calculated.

CalculateFunctions.CGRectGetCenter return the center point of a CGRect

那只是一个粗略的主意。实际上，您可以参考许多图书馆。一些建议：

• SPUserResizableView这正是您想要的ResizableView，但是它是用ObjC编写的，并且很长时间没有更新。但是您可以参考它。
• JLStickerTextView这可能无法很好地满足您的要求，因为它适合文本（编辑，调整大小，用一根手指旋转）。但是，这是用Swift编写的，这是一个很好的示例。

如有任何疑问，请随时发表。祝你好运:-)