Iphone 将CGGradient作为子层添加到UILabel会隐藏标签的文本

我想添加渐变作为标签的背景。我使用以下代码实现了这一点。但问题是，虽然渐变颜色出现在标签上，但文本不可见。请帮忙

lblPatientDetail.text=PatientsDetails;

lblPatientDetail.textColor=[UIColor blackColor];  

CAGradientLayer *gradient = [CAGradientLayer layer];
gradient.frame = lblPatientDetail.bounds;
gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor whiteColor] CGColor],(id)[[UIColor colorWithRed:255/255.0 green:239/255.0 blue:215/255.0 alpha:1.0] CGColor],nil];  

[lblPatientDetail.layer addSublayer:gradient];

lblPatientDetail.backgroundColor=[UIColor clearColor];

---

将子层插入到UILabel会隐藏文本，因此获得所需内容的最佳方法是将标签和渐变层添加到UIView

UIView *gradientLabelView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 100, 30)];

CAGradientLayer *gradient = [CAGradientLayer layer];
gradient.frame = gradientLabelView.bounds;
gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor whiteColor] CGColor],(id)[[UIColor colorWithRed:255/255.0 green:239/255.0 blue:215/255.0 alpha:1.0] CGColor],nil];

[gradientLabelView.layer addSublayer:gradient];

lblPatientDetail.frame = gradientLabelView.bounds;
lblPatientDetail.backgroundColor = [UIColor clearColor];
[gradientLabelView addSubview:lblPatientDetail];

[self addSubview:gradientLabelView];

---

我想你可以通过调整上面代码中的alpha值来创建渐变色

gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor whiteColor] CGColor],(id)[[UIColor colorWithRed:255/255.0 green:239/255.0 blue:215/255.0 alpha:0.1] CGColor],nil];

---

通过这样做，我能够获得渐变效果。

在UIView中使用UILabel的建议答案有效。显然，在给背景加上渐变色背景后，UILabel中不能有文本。。。不知道为什么

但这是解决方案的完整代码。。。。希望这对某人有帮助：）

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编码快乐

再思考一次来纠正答案。 如果使用自动布局来放置自定义视图，则可能会出现以下问题-

因此，视图的大小不同于子视图-UILabel和子层-渐变层

我通过增加一种方法来解决这个问题

class wResultView: UIView {
var label = UILabel()
var gradientLayer = CAGradientLayer()

override func layoutSubviews() {
    gradientLayer.frame = self.bounds
    label.frame = self.bounds
}
......

---

您可以在

UILabel

中添加

UILabel

像这样

class GradientLabel: UILabel {  

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)

        self.clipsToBounds = true
        DispatchQueue.main.async {
            self.applyGradient(with: Color.gradientColor, gradient: GradientOrientation.topLeftBottomRight)
            self.textColor = UIColor.white
        }
        DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + 0.1) {

            let label = UILabel(frame: CGRect(x: 0, y: 0, width: self.frame.size.width, height: self.frame.size.height))
            label.text = self.text
            label.font = self.font
            label.textColor = self.textColor
            label.textAlignment = self.textAlignment
            self.text = ""
            self.addSubview(label)
        }
    }
}

extension UIView {

    func applyGradient(with colours: [UIColor], locations: [NSNumber]? = nil) {
        let gradient = CAGradientLayer()
        gradient.frame = self.bounds
        gradient.colors = colours.map { $0.cgColor }
        gradient.locations = locations
        self.layer.insertSublayer(gradient, at: 0)
    }

    func applyGradient(with colours: [UIColor], gradient orientation: GradientOrientation) {
        let gradient = CAGradientLayer()
        gradient.frame = self.bounds
        gradient.colors = colours.map { $0.cgColor }
        gradient.startPoint = orientation.startPoint
        gradient.endPoint = orientation.endPoint
        self.layer.insertSublayer(gradient, at: 0)
    }
}

---

是的，我知道它被添加到文本上方：（…你能告诉我如何在后面添加这一层吗..我已经试过你建议的这一行了。它不起作用。我也更改了索引，但没有效果：）请帮助，提前谢谢：）我不确定，可能是你不能在UILabels上这样做。您可以尝试创建带有渐变的UIView，然后将标签添加为子视图。感谢James，我尝试了您的第二个选项：）在UIView上添加渐变，然后将标签添加为子视图：-）将修改后的UILabel的背景色更改为[UIColor clearColor]。如果不使用UILabel，则背景默认为whitebackground:p我们可以在不使用额外视图的情况下执行相同的操作吗

class GradientLabel: UILabel {  

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)

        self.clipsToBounds = true
        DispatchQueue.main.async {
            self.applyGradient(with: Color.gradientColor, gradient: GradientOrientation.topLeftBottomRight)
            self.textColor = UIColor.white
        }
        DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + 0.1) {

            let label = UILabel(frame: CGRect(x: 0, y: 0, width: self.frame.size.width, height: self.frame.size.height))
            label.text = self.text
            label.font = self.font
            label.textColor = self.textColor
            label.textAlignment = self.textAlignment
            self.text = ""
            self.addSubview(label)
        }
    }
}

extension UIView {

    func applyGradient(with colours: [UIColor], locations: [NSNumber]? = nil) {
        let gradient = CAGradientLayer()
        gradient.frame = self.bounds
        gradient.colors = colours.map { $0.cgColor }
        gradient.locations = locations
        self.layer.insertSublayer(gradient, at: 0)
    }

    func applyGradient(with colours: [UIColor], gradient orientation: GradientOrientation) {
        let gradient = CAGradientLayer()
        gradient.frame = self.bounds
        gradient.colors = colours.map { $0.cgColor }
        gradient.startPoint = orientation.startPoint
        gradient.endPoint = orientation.endPoint
        self.layer.insertSublayer(gradient, at: 0)
    }
}