//定義漸變的顏色 ? ? func returnBgview(bgview: UIView, isTopView: Bool) -> UIView {

????????var alphaStart = 0.0

? ? ? ? var alphaEnd = 0.5

? ? ? ? ? if isTopView {

? ? ? ? ? ? ????alphaStart = 0.5

? ? ? ? ? ? ????alphaEnd = 0.0

????????????} ?? ? ? ? ? ? ? ?

????????????let topColor = UIColor(red: 0/255, green: 0/255, blue: 0/255, alpha: CGFloat(alphaStart))

????? ? ? ? let buttomColor = UIColor(red: 0/255, green: 0/255, blue: 0/255, alpha: CGFloat(alphaEnd))

????? ? ? ? let gradientColors = [topColor.cgColor, buttomColor.cgColor]

? ? ? ? ? ? //定義每種顏色所在的位置

????? ? ? ? let gradientLocations:[NSNumber] = [0.0, 1.0]

? ? ? ? ? ? //創(chuàng)建CAGradientLayer對象并設(shè)置參數(shù)

????? ? ? ? let gradientLayer = CAGradientLayer()

????? ? ? ? ?gradientLayer.colors = gradientColors
????? ? ? ? ?gradientLayer.locations = gradientLocations

? ? ? ? ? ? ?//設(shè)置其CAGradientLayer對象的frame，并插入view的layer

????? ? ? ? gradientLayer.frame = bgview.bounds

????? ? ? ? bgview.layer.insertSublayer(gradientLayer, at: 0)

????? ? ? ? return bgview

????? ? }