在此问题之后,我可以为UINavigationBar
做一个背景梯度,但是当我尝试通过UIAppearance
设置它时,该应用程序在didFinishLaunching
中崩溃,因为没有当前的CGContext
。我该如何解决此问题,并且在应用程序委托中仍然拥有我的所有UIAppearance
代码?
didFinishLaunching
中的return true
之前被调用的代码:
private func setNavBarAppearance() {
let titleAttributes: [NSAttributedStringKey: Any] = [.foregroundColor: UIColor.white]
UINavigationBar.appearance().titleTextAttributes = titleAttributes
UINavigationBar.appearance().barTintColor = .white
UINavigationBar.appearance().tintColor = .white
UINavigationBar.appearance().makeTransparent()
// Set gradient
let colors = [UIColor.lavender.cgColor, UIColor.mint.cgColor]
let gradientLayer = CAGradientLayer()
gradientLayer.frame = UINavigationBar.appearance().bounds
gradientLayer.colors = colors
gradientLayer.startPoint = CGPoint(x: 0, y: 0.5)
gradientLayer.endPoint = CGPoint(x: 0.5, y: 0.5)
let image = UIImage(layer: gradientLayer)
UINavigationBar.appearance().setBackgroundImage(image, for: .default)
}
调用UIGraphicsBeginImageContext
时,必须提供非零的CGRect
。就我而言,我将框架设置为UINavigationBar.appearance().bounds
,该框架在应用程序委托中为零RECT。为了解决这个问题,我只需将梯度frame
设置为CGRect(x: 0, y: 0, width: UIScreen.main.bounds.width, height: 1)