Ios 为什么可以'；当我将UIView子类化时，我是否在图像上绘制？

我正在尝试使用来自的代码从摄影机卷上绘制图像。从照相机滚轮中选择照片后，

imageView

被设置为照片。当用户按下绘图按钮时，会在照片上方添加

tempImageView

，以便用户可以在照片上绘图。然而，当我试图在图像上画画时，什么也没有发生。为什么?

代码：

---

确保tempmageview.userIteractionEnabled=YES。默认情况下，UIImageView的此属性为否。

---

将断点放入GestureRecognitor方法后，查看是否正在调用该方法。

不必亲自尝试：至少在draw（）中将tempImageView的帧原点设置为（0,0）（也就是说，不要使用未更改的父边界），并在drawRect（）中绘制路径之前设置线宽

class EditViewController: UIViewController{
    var tempImageView: DrawableView!
    var imageView: UIImageView = UIImageView(image: UIImage(named: "ClearImage"))

    func draw(sender: UIButton!) {
        tempImageView = DrawableView(frame: imageView.bounds)
        tempImageView.backgroundColor = UIColor.clearColor()
        self.view.addSubview(tempImageView)
    }

}

class DrawableView: UIView {

let path=UIBezierPath()
var previousPoint:CGPoint
var lineWidth:CGFloat=10.0

// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
override init(frame: CGRect) {
    previousPoint=CGPoint.zero
    super.init(frame: frame)
}

required init?(coder aDecoder: NSCoder) {
    previousPoint=CGPoint.zero
    super.init(coder: aDecoder)
    let panGestureRecognizer=UIPanGestureRecognizer(target: self, action: "pan:")
    panGestureRecognizer.maximumNumberOfTouches=1
    self.addGestureRecognizer(panGestureRecognizer)
}

override func drawRect(rect: CGRect) {
    // Drawing code
    UIColor.greenColor().setStroke()
    path.stroke()
    path.lineWidth=lineWidth
}

func pan(panGestureRecognizer:UIPanGestureRecognizer)->Void
{
    let currentPoint=panGestureRecognizer.locationInView(self)
    let midPoint=self.midPoint(previousPoint, p1: currentPoint)

    if panGestureRecognizer.state == .Began
    {
        path.moveToPoint(currentPoint)
    }
    else if panGestureRecognizer.state == .Changed
    {
        path.addQuadCurveToPoint(midPoint,controlPoint: previousPoint)
    }

    previousPoint=currentPoint
    self.setNeedsDisplay()
}

func midPoint(p0:CGPoint,p1:CGPoint)->CGPoint
{
    let x=(p0.x+p1.x)/2
    let y=(p0.y+p1.y)/2
    return CGPoint(x: x, y: y)
}

}