向 tableview 添加渐变会隐藏内容

Question

我有一个表格视图，它运行良好。但我必须在背景上添加渐变。我在 viewDidLoad 中用这段代码做到了：

gradientLayer.frame = self.view.bounds
let color1 = UIColor.blueColor().CGColor as CGColorRef
let color2 = UIColor.redColor().CGColor as CGColorRef
gradientLayer.colors = [color1, color2]
gradientLayer.locations = [0.0, 1.0]
gradientLayer.startPoint = CGPoint(x: 1, y: 0)
gradientLayer.endPoint = CGPoint(x: 0, y: 0)
self.view.layer.addSublayer(gradientLayer)
self.view.backgroundColor = UIColor.greenColor()

但现在我没有看到我的 tableview 的任何内容。

Answer 1

要适当配置背景渐变，您可以使用UITableView 的backgroundView 属性和带有CAGradientLayer 的视图。生成的代码（在 Swift 3 中）将是：

/* A small UIView subclass displaying gradient */

class GradientView: UIView {

    /* Overriding default layer class to use CAGradientLayer */
    override class var layerClass: AnyClass {
        return CAGradientLayer.self
    }

    /* Handy accessor to avoid unnecessary casting */
    private var gradientLayer: CAGradientLayer {
        return layer as! CAGradientLayer
    }

    /* Public properties to manipulate colors */
    public var fromColor: UIColor = UIColor.red {
        didSet {
            var currentColors = gradientLayer.colors
            currentColors![0] = fromColor.cgColor
            gradientLayer.colors = currentColors
        }
    }

    public var toColor: UIColor = UIColor.blue {
        didSet {
            var currentColors = gradientLayer.colors
            currentColors![1] = toColor.cgColor
            gradientLayer.colors = currentColors
        }
    }

    /* Initializers overriding to have appropriately configured layer after creation */
    override init(frame: CGRect) {
        super.init(frame: frame)
        gradientLayer.colors = [fromColor.cgColor, toColor.cgColor]
        gradientLayer.startPoint = CGPoint(x: 0, y: 0.5)
        gradientLayer.endPoint = CGPoint(x: 1.0, y: 0.5)
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        gradientLayer.colors = [fromColor.cgColor, toColor.cgColor]
        gradientLayer.startPoint = CGPoint(x: 0, y: 0.5)
        gradientLayer.endPoint = CGPoint(x: 1.0, y: 0.5)
    }
}


/* Code that should be called in viewDidLoad method */

class MyViewController: UITableViewController {

    /* ... */

    override func viewDidLoad() {
        super.viewDidLoad()
        tableView.backgroundView = GradientView()
    }

    /* ... */

}