Xcode iOS Notability"缩放框"

Question

Notability和其他笔记应用程序具有此"缩放框"功能,您可以在底部的放大框中绘制.用户还可以拖动顶部的框以更改底部放大的内容.我已经尝试了我能想到的所有内容,以便在我的应用中添加此功能.我在两个视图中添加了相同的文档,但后来我遇到了很多内存问题,我复制了文件,但又重复了内存问题.有谁知道一个简单的方法来做到这一点？无论如何我可以只有一个放大另一个视图的视图？

Answer 1

创建一个新的 Cocoa Touch 类（可以将其命名为 MagnifyView）并将其设置为 UIView 的子类 在您的类中添加以下代码：

var viewToMagnify: UIView!
var touchPoint: CGPoint!

override init(frame: CGRect)
{
    super.init(frame: frame)
    commonInit()
}

required init?(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)
    commonInit()
}

func commonInit()
{
    // Set border color, border width and corner radius of the magnify view
    self.layer.borderColor = UIColor.lightGray.cgColor
    self.layer.borderWidth = 3
    self.layer.cornerRadius = 50
    self.layer.masksToBounds = true
}

func setTouchPoint(pt: CGPoint)
{
    touchPoint = pt
    self.center = CGPoint(x: pt.x, y: pt.y - 100)
}

override func draw(_ rect: CGRect) {
    let context = UIGraphicsGetCurrentContext()
    context!.translateBy(x: 1 * (self.frame.size.width * 0.5), y: 1 * (self.frame.size.height * 0.5))
    context!.scaleBy(x: 1.5, y: 1.5) // 1.5 is the zoom scale
    context!.translateBy(x: -1 * (touchPoint.x), y: -1 * (touchPoint.y))
    self.viewToMagnify.layer.render(in: context!)
}

要使用它，请在您想要具有放大效果的视图控制器中实现touchesBegan、touchesMoved和touchesEnd函数。

具体方法如下：

override func touchesBegan(_ touches: Set, with event: UIEvent?) {
    let point = touches.first?.location(in: self.view)
    if magnifyView == nil
    {
        magnifyView = MagnifyView.init(frame: CGRect(x: 0, y: 0, width: 100, height: 100))
        magnifyView.viewToMagnify = self.view
        magnifyView.setTouchPoint(pt: point!)
        self.view.addSubview(magnifyView)
    }
}

override func touchesEnded(_ touches: Set, with event: UIEvent?) {
    if magnifyView != nil
    {
        magnifyView.removeFromSuperview()
        magnifyView = nil
    }
}

override func touchesMoved(_ touches: Set, with event: UIEvent?) {
    let point = touches.first?.location(in: self.view)
    magnifyView.setTouchPoint(pt: point!)
    magnifyView.setNeedsDisplay()
}

原始来源在这里