如何制作UIView的渐变边框？

Question

我想制作一个如下图所示的渐变边框:

但我不知道它究竟是怎么做的,即我应该用它做什么渐变色？如何设置我的视图以显示像图像的边框？

我正在使用以下代码来获取边框:

 self.view.layer.borderColor = [UIColor orangeColor].CGColor;
 self.view.layer.borderWidth = 2.0f;

Answer 1

这就是我做的,它完美地运作

   extension CALayer {
    func addGradienBorder(colors:[UIColor],width:CGFloat = 1) {
        let gradientLayer = CAGradientLayer()
        gradientLayer.frame =  CGRect(origin: CGPointZero, size: self.bounds.size)
        gradientLayer.startPoint = CGPointMake(0.0, 0.5)
        gradientLayer.endPoint = CGPointMake(1.0, 0.5)
        gradientLayer.colors = colors.map({$0.CGColor})

        let shapeLayer = CAShapeLayer()
        shapeLayer.lineWidth = width
        shapeLayer.path = UIBezierPath(rect: self.bounds).CGPath
        shapeLayer.fillColor = nil
        shapeLayer.strokeColor = UIColor.blackColor().CGColor
        gradientLayer.mask = shapeLayer

        self.addSublayer(gradientLayer)
    }

}

Answer 2

感谢蒂亚戈·门德斯的回答。

我改进了功能：

• 添加角半径。

并修复了一些问题以确保正确的屏蔽和给定的边框宽度：

• 改进的渐变层框架；
• 改进了掩码路径舍入矩形。

斯威夫特 5

public extension UIView {

    private static let kLayerNameGradientBorder = "GradientBorderLayer"

    func gradientBorder(width: CGFloat,
                        colors: [UIColor],
                        startPoint: CGPoint = CGPoint(x: 0.5, y: 0.0),
                        endPoint: CGPoint = CGPoint(x: 0.5, y: 1.0),
                        andRoundCornersWithRadius cornerRadius: CGFloat = 0) {

        let existingBorder = gradientBorderLayer()
        let border = existingBorder ?? CAGradientLayer()
        border.frame = CGRect(x: bounds.origin.x, y: bounds.origin.y,
                              width: bounds.size.width + width, height: bounds.size.height + width)
        border.colors = colors.map { return $0.cgColor }
        border.startPoint = startPoint
        border.endPoint = endPoint

        let mask = CAShapeLayer()
        let maskRect = CGRect(x: bounds.origin.x + width/2, y: bounds.origin.y + width/2,
                              width: bounds.size.width - width, height: bounds.size.height - width)
        mask.path = UIBezierPath(roundedRect: maskRect, cornerRadius: cornerRadius).cgPath
        mask.fillColor = UIColor.clear.cgColor
        mask.strokeColor = UIColor.white.cgColor
        mask.lineWidth = width

        border.mask = mask

        let exists = (existingBorder != nil)
        if !exists {
            layer.addSublayer(border)
        }
    }
    private func gradientBorderLayer() -> CAGradientLayer? {
        let borderLayers = layer.sublayers?.filter { return $0.name == UIView.kLayerNameGradientBorder }
        if borderLayers?.count ?? 0 > 1 {
            fatalError()
        }
        return borderLayers?.first as? CAGradientLayer
    }
}

为了更易读地声明startPoint和endPoint渐变层，我使用以下代码：

public extension CGPoint {

    enum CoordinateSide {
        case topLeft, top, topRight, right, bottomRight, bottom, bottomLeft, left
    }

    static func unitCoordinate(_ side: CoordinateSide) -> CGPoint {
        switch side {
        case .topLeft:      return CGPoint(x: 0.0, y: 0.0)
        case .top:          return CGPoint(x: 0.5, y: 0.0)
        case .topRight:     return CGPoint(x: 1.0, y: 0.0)
        case .right:        return CGPoint(x: 0.0, y: 0.5)
        case .bottomRight:  return CGPoint(x: 1.0, y: 1.0)
        case .bottom:       return CGPoint(x: 0.5, y: 1.0)
        case .bottomLeft:   return CGPoint(x: 0.0, y: 1.0)
        case .left:         return CGPoint(x: 1.0, y: 0.5)
        }
    }
}

所以最后的用法是：

view.gradientBorder(width: 3, colors: [.red, .orange], startPoint: .unitCoordinate(.top), endPoint: .unitCoordinate(.bottom), andRoundCornersWithRadius: 12)

Answer 3

您可以使用此方法制作视场和拐角半径的渐变边界-

self.yourView.layer.cornerRadius=4;

self.yourView.layer.masksToBounds=YES;

CAGradientLayer *gradient = [CAGradientLayer layer];

gradient.frame = self.yourView.bounds;

gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor colorWithRed:255/255.0 green:226/255.0 blue:138/255.0 alpha:1.0] CGColor], (id)[[UIColor colorWithRed:255/255.0 green:198/255.0 blue:91/255.0 alpha:0.9] CGColor],(id)[[UIColor colorWithRed:255/255.0 green:226/255.0 blue:138/255.0 alpha:1.0] CGColor], nil];

gradient.startPoint = CGPointMake(0.0, 0.0);

gradient.endPoint = CGPointMake(1, 1);

CAShapeLayer *shapeLayer =[[CAShapeLayer alloc] init];

shapeLayer.lineWidth = 15; // higher number higher border width

shapeLayer.path = [UIBezierPath bezierPathWithRect:self.yourView.bounds].CGPath;

shapeLayer.fillColor = nil;

shapeLayer.strokeColor = [UIColor blackColor].CGColor;

gradient.mask = shapeLayer;

[self.yourView.layer insertSublayer:gradient atIndex:0];

这会帮助你！谢谢

Answer 4

以下是使用 Core Graphics 的方法。创建一个 UIView 子类，并在其中drawRect:创建一个渐变并用黑色内容矩形覆盖它：

- (void)drawRect:(CGRect)rect
{
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

    // Create and draw the gradient
    UIColor *gradientColorTop = [UIColor orangeColor];
    UIColor *gradientColorBottom = [UIColor yellowColor];
    NSArray *gradientColors = @[(id) gradientColorTop.CGColor, (id) gradientColorBottom.CGColor];
    CGFloat locations[] = {0.1, 0.80};

    CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (__bridge CFArrayRef)(gradientColors), locations);

    CGPoint startPoint = CGPointMake(CGRectGetMidX(rect), CGRectGetMinY(rect));
    CGPoint endPoint = CGPointMake(CGRectGetMidX(rect), CGRectGetMaxY(rect));

    UIBezierPath *gradientBorder = [UIBezierPath bezierPathWithRoundedRect:rect
    byRoundingCorners:UIRectCornerAllCorners cornerRadii:CGSizeMake(10.0, 10.0)];
    [gradientBorder addClip];

    CGContextDrawLinearGradient(ctx, gradient, startPoint, endPoint, 0);

    // Draw the inner content rectangle
    UIBezierPath *contentPath = [UIBezierPath bezierPathWithRect:CGRectInset(rect, 20.0, 20.0)];
    [[UIColor blackColor] setFill];
    [contentPath fill];

    CGGradientRelease(gradient);
    CGColorSpaceRelease(colorSpace);
}

这会产生与您想要实现的结果类似的结果。