Swift - UIView框架不等于UIView.layer.frame

Question

我想绘制一个UIView图层，但是当我这样做时，图层框架与UIView框架不相等（在预览中）。

class ViewController: UIViewController {

    var graphHeight:CGFloat = 100
    var graphSize:CGFloat!

    override func viewDidLoad() {
        super.viewDidLoad()
        graphSize = self.view.frame.height/CGFloat(M_PI)
        let graphRect:CGRect = CGRectMake(0, graphHeight, self.view.frame.width, graphSize)
        let background = blueGardient()
        var theView:UIView = UIView(frame: graphRect)
        background.frame = theView.frame
        theView.backgroundColor = UIColor.yellowColor()
        theView.layer.cornerRadius = 8
        theView.layer.borderWidth = 1
        theView.layer.borderColor = UIColor.redColor().CGColor
        theView.layer.insertSublayer(background, atIndex: 0)
        self.view.addSubview(theView)

    }

    func blueGardient()->CAGradientLayer{
        let topColor = UIColor(red: 0, green: 0, blue: 255, alpha: 0.7)
        let bottomColor = UIColor(red: 0, green: 0, blue: 255, alpha: 0.9)
        let gradientColors: [CGColor] = [topColor.CGColor, bottomColor.CGColor]
        let gradientLocations: [Float] = [0.0, 1.0]
        let gradientLayer: CAGradientLayer = CAGradientLayer()
        gradientLayer.colors = gradientColors
        gradientLayer.locations = gradientLocations
        return gradientLayer
    }
}

框架相等

(0.0,100.0,320.0,180.800015352393)
(0.0,100.0,320.0,180.800015352393)

但未显示eauql。我尝试使用theView.layer.frame但没有成功......

Answer 1

问题是因为每个帧的上下文不同。您的视图框架（theView.frame）位于其超视图的上下文中，因此（0,100）原点意味着它从屏幕左上方向下偏移100个点。图层的框架（background.frame）位于视图所属的（theView）的上下文中，因此相同的（0,100）原点表示蓝色图层从视图的左上角偏移100点。

不使用视图frame，而是使用视图bounds和（0,0）原点的大小创建一个新的rect：

background.frame = CGRect(origin: CGPointZero, size: theView.bounds.size)