ios - SwiftUI 中文本的渐变作为前景色

Question

有没有办法在 SwiftUI 中使用渐变作为文本的前景色？

感谢您的提前答复!

Answer 1

我已经用新答案更新了我的答案，您可以尝试一下。旧的答案仍然可用。

新答案

import SwiftUI

struct GradientText: View {
    var body: some View {
        Text("Gradient foreground")
            .gradientForeground(colors: [.red, .blue])
            .padding(.horizontal, 20)
            .padding(.vertical)
            .background(Color.green)
            .cornerRadius(10)
            .font(.title)
       }
}

extension View {
    public func gradientForeground(colors: [Color]) -> some View {
        self.overlay(
            LinearGradient(
                colors: colors,
                startPoint: .topLeading,
                endPoint: .bottomTrailing)
        )
            .mask(self)
    }
}

输出

<小时/>

旧答案

在 SwiftUI 中，您也可以这样做，如下所示，使用 Add gradient color to text 的概念

渐变 View :

struct GradientView: View {
    var body: some View {
        VStack {
            GradientLabelWrapper(width: 150) //  you can give as you want
                .frame(width: 200, height: 200, alignment: .center) // set frame as you want
        }
    }
}

渐变标签包装器:

struct GradientLabelWrapper: UIViewRepresentable {

    var width: CGFloat
    var text: String?
    typealias UIViewType = UIView
    
    func makeUIView(context: UIViewRepresentableContext<GradientLabelWrapper>) -> UIView {
    
        let label = UILabel()
        label.lineBreakMode = .byWordWrapping
        label.numberOfLines = 0
        label.preferredMaxLayoutWidth = width
        label.text = text ?? ""
        label.font = UIFont.systemFont(ofSize: 25) //set as you need
        label.applyGradientWith(startColor: .red, endColor: .blue)
        return label
    }

    func updateUIView(_ uiView: UIView, context: UIViewRepresentableContext<GradientLabelWrapper>) {
    }
} 

UILabel:扩展

extension UILabel {

    func applyGradientWith(startColor: UIColor, endColor: UIColor) {
        
        var startColorRed:CGFloat = 0
        var startColorGreen:CGFloat = 0
        var startColorBlue:CGFloat = 0
        var startAlpha:CGFloat = 0
        
        if !startColor.getRed(&startColorRed, green: &startColorGreen, blue: &startColorBlue, alpha: &startAlpha) {
            return
        }
        
        var endColorRed:CGFloat = 0
        var endColorGreen:CGFloat = 0
        var endColorBlue:CGFloat = 0
        var endAlpha:CGFloat = 0
        
        if !endColor.getRed(&endColorRed, green: &endColorGreen, blue: &endColorBlue, alpha: &endAlpha) {
            return
        }
        
        let gradientText = self.text ?? ""
        
        let textSize: CGSize = gradientText.size(withAttributes: [NSAttributedString.Key.font:self.font!])
        let width:CGFloat = textSize.width
        let height:CGFloat = textSize.height
        
        UIGraphicsBeginImageContext(CGSize(width: width, height: height))
        
        guard let context = UIGraphicsGetCurrentContext() else {
            UIGraphicsEndImageContext()
            return
        }
        
        UIGraphicsPushContext(context)
        
        let glossGradient:CGGradient?
        let rgbColorspace:CGColorSpace?
        let num_locations:size_t = 2
        let locations:[CGFloat] = [ 0.0, 1.0 ]
        let components:[CGFloat] = [startColorRed, startColorGreen, startColorBlue, startAlpha, endColorRed, endColorGreen, endColorBlue, endAlpha]
        rgbColorspace = CGColorSpaceCreateDeviceRGB()
        glossGradient = CGGradient(colorSpace: rgbColorspace!, colorComponents: components, locations: locations, count: num_locations)
        let topCenter = CGPoint.zero
        let bottomCenter = CGPoint(x: 0, y: textSize.height)
        context.drawLinearGradient(glossGradient!, start: topCenter, end: bottomCenter, options: CGGradientDrawingOptions.drawsBeforeStartLocation)
        
        UIGraphicsPopContext()
        
        guard let gradientImage = UIGraphicsGetImageFromCurrentImageContext() else {
            UIGraphicsEndImageContext()
            return
        }
        
        UIGraphicsEndImageContext()
        self.textColor = UIColor(patternImage: gradientImage)
    }
}