Swift 带有渐变文本颜色的自定义UILabel始终变为黑色
我创建了一个自定义UILabel来显示grediant文本,但它总是将文本显示为黑色…当我在视图控制器上使用相同的代码时,它会工作Swift 带有渐变文本颜色的自定义UILabel始终变为黑色,swift,text,colors,uilabel,gradient,Swift,Text,Colors,Uilabel,Gradient,我创建了一个自定义UILabel来显示grediant文本,但它总是将文本显示为黑色…当我在视图控制器上使用相同的代码时,它会工作 import UIKit class GradientLabel: UILabel { override func awakeFromNib() { super.awakeFromNib() let gredient = GradientView.init(frame: CGRect(x: 0, y: 0, width:
import UIKit
class GradientLabel: UILabel {
override func awakeFromNib() {
super.awakeFromNib()
let gredient = GradientView.init(frame: CGRect(x: 0, y: 0, width: frame.size.width, height: frame.size.height))
gredient.bottomColor = #colorLiteral(red: 0.1764705926, green: 0.4980392158, blue: 0.7568627596, alpha: 1)
gredient.topColor = #colorLiteral(red: 0.1764705926, green: 0.01176470611, blue: 0.5607843399, alpha: 1)
setTextColorToGradient(image: imageWithView(view: gredient)!)
}
func imageWithView(view: UIView) -> UIImage? {//bet7awel uiview to image
UIGraphicsBeginImageContextWithOptions(view.bounds.size, view.isOpaque, 0.0)
view.drawHierarchy(in: view.bounds, afterScreenUpdates: true)
let img = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return img
}
func setTextColorToGradient(image: UIImage) {//beta7'od image we tekteb beha el text fe el label
UIGraphicsBeginImageContext(frame.size)
image.draw(in: bounds)
let myGradient = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
textColor = UIColor(patternImage: myGradient!)
}
}
您应该
init
您的标签,而不是awakeFromNib
因为您的标签没有使用xib
class GradientLabel: UILabel {
override init(frame: CGRect) {
super.init(frame: frame)
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
}
扩展将非常适合使代码可重用
extension UILabel {
func setTextColorToGradient(_ image: UIImage) {
UIGraphicsBeginImageContext(frame.size)
image.draw(in: bounds)
let myGradient = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
textColor = UIColor(patternImage: myGradient!)
}
}
用法:
label.setTextColorToGradient(UIImage(named:"someImage")!)
您不想依赖于
awakeFromNib
。此外,您也确实不希望在init
中执行此操作,因为您希望能够响应大小更改(例如,如果您有约束,并且在首次创建标签后,框架发生更改)
相反,从布局子视图
更新渐变,每当视图的帧
更改时,都会调用该渐变:
@IBDesignable
class GradientLabel: UILabel {
@IBInspectable var topColor: UIColor = #colorLiteral(red: 0.1764705926, green: 0.4980392158, blue: 0.7568627596, alpha: 1) {
didSet { setNeedsLayout() }
}
@IBInspectable var bottomColor: UIColor = #colorLiteral(red: 0.1764705926, green: 0.01176470611, blue: 0.5607843399, alpha: 1) {
didSet { setNeedsLayout() }
}
override func layoutSubviews() {
super.layoutSubviews()
updateTextColor()
}
private func updateTextColor() {
let image = UIGraphicsImageRenderer(bounds: bounds).image { _ in
let gradient = GradientView(frame: bounds)
gradient.topColor = topColor
gradient.bottomColor = bottomColor
gradient.drawHierarchy(in: bounds, afterScreenUpdates: true)
}
textColor = UIColor(patternImage: image)
}
}
这导致:
注意
- 我使用了新的
uigraphicsimageender
,而不是UIGraphicsBeginImageContext
,UIGraphicsGetImageFromCurrentImageContext
,以及uigraphicsSendImageContext
- 我没有手动构建
CGRect
,而是使用bounds
- 我已经将它设置为可设计的,这样我就可以在Interface Builder中直接使用它了。我还将颜色设置为可检测的
@IB,这样您就可以在IB中正确调整颜色,而不用去编码了。显然,只有在希望看到IB中渲染的渐变效果时才需要这样做
值得一提的是,这是我在本例中使用的
GradientView
:
@IBDesignable
class GradientView: UIView {
override class var layerClass: AnyClass { return CAGradientLayer.self }
private var gradientLayer: CAGradientLayer { return layer as! CAGradientLayer }
@IBInspectable var topColor: UIColor = .white { didSet { updateColors() } }
@IBInspectable var bottomColor: UIColor = .blue { didSet { updateColors() } }
override init(frame: CGRect = .zero) {
super.init(frame: frame)
updateColors()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
updateColors()
}
private func updateColors() {
gradientLayer.colors = [topColor.cgColor, bottomColor.cgColor]
}
}
在这种情况下,因为我们将layerClass
设置为渐变,所以我们需要做的就是在init
期间对其进行配置,而基本layerClass
将负责响应大小更改
或者,您可以使用CoreGraphics绘制渐变:
@IBDesignable
class GradientLabel: UILabel {
@IBInspectable var topColor: UIColor = #colorLiteral(red: 0.1764705926, green: 0.4980392158, blue: 0.7568627596, alpha: 1) {
didSet { setNeedsLayout() }
}
@IBInspectable var bottomColor: UIColor = #colorLiteral(red: 0.1764705926, green: 0.01176470611, blue: 0.5607843399, alpha: 1) {
didSet { setNeedsLayout() }
}
override func layoutSubviews() {
super.layoutSubviews()
updateTextColor()
}
private func updateTextColor() {
let image = UIGraphicsImageRenderer(bounds: bounds).image { context in
let colors = [topColor.cgColor, bottomColor.cgColor]
guard let gradient = CGGradient(colorsSpace: nil, colors: colors as CFArray, locations: nil) else { return }
context.cgContext.drawLinearGradient(gradient,
start: CGPoint(x: bounds.midX, y: bounds.minY),
end: CGPoint(x: bounds.midX, y: bounds.maxY),
options: [])
}
textColor = UIColor(patternImage: image)
}
}
这实现了与第一个示例相同的效果,但可能会有一点效率。如果您在代码中创建标签,则不会调用awakeFromNib。此外,您的帧提取得太早。请尝试此库:非常感谢您的帮助和专业澄清……它工作得非常好:)