不能改变UIView背景颜色从黑色

Question

这是我第一次遇到drawRect问题.我有一个简单的UIView子类,其中有一个填充路径.一切都好.路径被正确填充,但无论如何背景都保持黑色.我该怎么办？我的代码如下:

var color: UIColor = UIColor.red {didSet{setNeedsDisplay()}}

private var spaceshipBezierPath: UIBezierPath{
    let path = UIBezierPath()
    let roomFromTop: CGFloat = 10
    let roomFromCenter: CGFloat = 7
    path.move(to: CGPoint(x: bounds.minX, y: bounds.maxY))
    path.addLine(to: CGPoint(x: bounds.minX, y: bounds.minY+roomFromTop))
    path.addLine(to: CGPoint(x: bounds.midX-roomFromCenter, y: bounds.minY+roomFromTop))
    path.addLine(to: CGPoint(x: bounds.midX-roomFromCenter, y: bounds.minY))
    path.addLine(to: CGPoint(x: bounds.midX+roomFromCenter, y: bounds.minY))
    path.addLine(to: CGPoint(x: bounds.midX+roomFromCenter, y: bounds.minY+roomFromTop))
    path.addLine(to: CGPoint(x: bounds.maxX, y: bounds.minY+roomFromTop))
    path.addLine(to: CGPoint(x: bounds.maxX, y: bounds.maxY))
    path.addLine(to: CGPoint(x: bounds.minX, y: bounds.maxY))
    return path
}

override func draw(_ rect: CGRect) {
    color.setFill()
    spaceshipBezierPath.fill()
}

以下是视图的样子:

Answer 1

我有一个简单的UIView子类......但无论如何,背景都是黑色的

通常这种情况是因为您忘记将UIView子类设置isOpaque为false.在UIView子类的初始化程序中执行此操作是个好主意,以使其足够早.

例如,我在这里稍微调整了您的代码.这是我正在使用的完整代码:

class MyView : UIView {
    private var spaceshipBezierPath: UIBezierPath{
        let path = UIBezierPath()
        // ... identical to your code
        return path
    }
    override func draw(_ rect: CGRect) {
        UIColor.red.setFill()
        spaceshipBezierPath.fill()
    }
}

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()        
        let v = MyView(frame:CGRect(x: 100, y: 100, width: 200, height: 200))
        self.view.addSubview(v)
    }
}

注意黑色背景:

现在我将这些行添加到MyView:

override init(frame:CGRect) {
    super.init(frame:frame)
    self.isOpaque = false
}
required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
}

看看有什么区别？