背景渐变：在Objective C中从左到右线性渐变。

Question

我的客户希望此背景视图具有渐变效果。 背景渐变：rgb（118,118,118）|＃ffffff | rgb（198,198,197）从左到右线性 我已尝试过这种方式，但它是纵向的，我想要横向的。

UIColor *leftColor = [UIColor colorWithRed:118.0/255.0 green:118.0/255.0 blue:118.0/255.0 alpha:1.0];
UIColor *middleColor = [UIColor colorWithRed:255.0/255.0 green:255.0/255.0 blue:255.0/255.0 alpha:1.0];
UIColor *rightColor = [UIColor colorWithRed:198.0/255.0 green:198.0/255.0 blue:197.0/255.0 alpha:1.0];

// Create the gradient
CAGradientLayer *theViewGradient = [CAGradientLayer layer];
theViewGradient.colors = [NSArray arrayWithObjects: (id)leftColor.CGColor, (id)middleColor.CGColor,(id)rightColor.CGColor, nil];
theViewGradient.frame = self.view.bounds;
//Add gradient to view
[self.view.layer insertSublayer:theViewGradient atIndex:0];

像这样吗？

- Harshit Goel

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[gradient setStartPoint:CGPointMake(0, 0)]; [gradient setEndPoint:CGPointMake(0, 1)];在渐变中添加起始点和终止点。 - Harshal Valanda

@harshal 非常有帮助！ theViewGradient.startPoint = CGPointMake(0.0, 0.0); theViewGradient.endPoint = CGPointMake(1.0, 0.0); - Harshit Goel

Answer 1

您需要设置渐变层（gradientLayer）的 startPoint 和 endPoint 属性。它们分别代表第一种颜色的起始坐标和最后一种颜色的终点坐标。

它们都是 CGPoint 类型，并且它们的 x 和 y 值应该在 0.0 到 1.0 之间。

默认情况下，startPoint 的坐标为 (0.5, 0.0)，而 endPoint 的坐标为 (0.5, 1.0)。

(0.0, 0.0) 是左上角，而 (1.0, 1.0) 是右下角。

因此，请尝试：

theViewGradient.startPoint = CGPointMake(0.0, 0.5);
theViewGradient.endPoint = CGPointMake(1.0, 0.5);

- Ocunidee

Answer 2

在Swift 3.0和4.0中，从左到右的方法是：

    gradientLayer.startPoint = CGPoint(x: 0.0, y: 0.5)
    gradientLayer.endPoint = CGPoint(x: 1.0, y: 0.5)

- Chatar Veer Suthar

Answer 3

 **The start and end points of the gradient when drawn into the layer's
 coordinate space. The start point corresponds to the first gradient
 stop, the end point to the last gradient stop. Both points are
 defined in a unit coordinate space that is then mapped to the
 layer's bounds rectangle when drawn. (i.e. [0,0] is the bottom-left
 corner of the layer, [1,1] is the top-right corner.).The default values
 are [.5,0] and [.5,1] respectively.** 

theViewGradient.startPoint = CGPointMake(0.0, 0.5);
theViewGradient.endPoint = CGPointMake(1.0, 0.5);

- Jagveer Singh

Answer 4

 enum GradiantDirection {
        case leftToRight
        case rightToLeft
        case topToBottom
        case bottomToTop
    }
    
 class  func setGradiantColor(view : UIView, topColor : UIColor, bottomColor:UIColor, cornerRadius : CGFloat = 0.0,gradiantDirection : GradiantDirection = .topToBottom )
    {
        
        view.layer.sublayers?.filter{ $0 is CAGradientLayer }.forEach{ $0.removeFromSuperlayer() }
        
        let gradient: CAGradientLayer = CAGradientLayer()
        gradient.colors = [topColor.cgColor,bottomColor.cgColor]
        gradient.frame = view.bounds
        
        switch gradiantDirection {
        case .topToBottom:
            gradient.startPoint = CGPoint(x: 0.0, y: 0.0)
            gradient.endPoint = CGPoint(x: 0.0, y: 1.0)
        case .bottomToTop:
            gradient.startPoint = CGPoint(x: 1.0, y: 0.5)
            gradient.endPoint = CGPoint(x: 0.0, y: 0.5)
        case .leftToRight:
            gradient.startPoint = CGPoint(x: 0.0, y: 0.5)
            gradient.endPoint = CGPoint(x: 1.0, y: 0.5)
        case .rightToLeft:
            gradient.startPoint = CGPoint(x: 1.0, y: 0.5)
            gradient.endPoint = CGPoint(x: 0.0, y: 0.5)
        }
        
        gradient.masksToBounds = true
        let gradientLayer = CAGradientLayer()
        gradientLayer.cornerRadius = cornerRadius
        gradient.rasterizationScale = 100
        view.layer.insertSublayer(gradient, at: 0)
    }

- Ali A. Jalil