我正在尝试使用 CaGradientLayer
绘制角度渐变。我知道可以使用 startPoint
和 endPoint
来定义角度。对于一些标准的角度,如0、90、180、360等,我可以计算这些点。但是我想为任意角度制定这些点。我尝试使用一些三角学计算它,但没有成功。有人可以给我指引如何为任意角度计算这些点吗?
我正在尝试使用 CaGradientLayer
绘制角度渐变。我知道可以使用 startPoint
和 endPoint
来定义角度。对于一些标准的角度,如0、90、180、360等,我可以计算这些点。但是我想为任意角度制定这些点。我尝试使用一些三角学计算它,但没有成功。有人可以给我指引如何为任意角度计算这些点吗?
static func setGradient(view: UIView!,viewRadius: CGFloat!, color1: UIColor!, color2: UIColor!, angle: Double!, alphaValue: CGFloat!){
let gradient = CAGradientLayer()
gradient.frame = CGRect(origin: CGPoint.zero, size: view.frame.size)
gradient.colors = [color1.withAlphaComponent(alphaValue).cgColor, color2.withAlphaComponent(alphaValue).cgColor]
let x: Double! = angle / 360.0
let a = pow(sinf(Float(2.0 * M_PI * ((x + 0.75) / 2.0))),2.0);
let b = pow(sinf(Float(2*M_PI*((x+0.0)/2))),2);
let c = pow(sinf(Float(2*M_PI*((x+0.25)/2))),2);
let d = pow(sinf(Float(2*M_PI*((x+0.5)/2))),2);
gradient.endPoint = CGPoint(x: CGFloat(c),y: CGFloat(d))
gradient.startPoint = CGPoint(x: CGFloat(a),y:CGFloat(b))
view.roundCorners([.topLeft, .bottomLeft], radius: viewRadius)
view.layer.insertSublayer(gradient, at: 0)
}
这是基于Sarthak Sharma的解决方案而来。我扩展了UIView,并且发现可读性和类型转换可以有所改进:
extension UIView {
func setGradient(colors: [CGColor], angle: Float = 0) {
let gradientLayerView: UIView = UIView(frame: CGRect(x:0, y: 0, width: bounds.width, height: bounds.height))
let gradient: CAGradientLayer = CAGradientLayer()
gradient.frame = gradientLayerView.bounds
gradient.colors = colors
let alpha: Float = angle / 360
let startPointX = powf(
sinf(2 * Float.pi * ((alpha + 0.75) / 2)),
2
)
let startPointY = powf(
sinf(2 * Float.pi * ((alpha + 0) / 2)),
2
)
let endPointX = powf(
sinf(2 * Float.pi * ((alpha + 0.25) / 2)),
2
)
let endPointY = powf(
sinf(2 * Float.pi * ((alpha + 0.5) / 2)),
2
)
gradient.endPoint = CGPoint(x: CGFloat(endPointX),y: CGFloat(endPointY))
gradient.startPoint = CGPoint(x: CGFloat(startPointX), y: CGFloat(startPointY))
gradientLayerView.layer.insertSublayer(gradient, at: 0)
layer.insertSublayer(gradientLayerView.layer, at: 0)
}
}
将以下代码添加到新的或相关的Swift文件中,然后您只需调用myView.setGradient(colors: gradientColorsArray)
或myView.setGradient(colors: gradientColorsArray, angle: 90)
即可。
-(UIView *)gradientViewWithFrame:(CGRect)frame colourA:(UIColor *)A colourB:(UIColor *)B rotation:(float)x {
//x is between 0 and 1, eg. from a slider, representing 0 - 360 degrees
//colour A starts on top, with colour B below
//rotations move anti-clockwise
//1. create the colour view
UIView * colourView = [UIView new];
colourView.frame = frame;
//2. create the gradient layer
CAGradientLayer *gradient = [CAGradientLayer layer];
gradient.frame = colourView.bounds;
gradient.colors = [NSArray arrayWithObjects:(id)[A CGColor], (id)[B CGColor], nil];
[colourView.layer insertSublayer:gradient atIndex:0];
//3. create coordinates
float a = pow(sinf((2*M_PI*((x+0.75)/2))),2);
float b = pow(sinf((2*M_PI*((x+0.0)/2))),2);
float c = pow(sinf((2*M_PI*((x+0.25)/2))),2);
float d = pow(sinf((2*M_PI*((x+0.5)/2))),2);
//4. set the gradient direction
[gradient setStartPoint:CGPointMake(a, b)];
[gradient setEndPoint:CGPointMake(c, d)];
return colourView;
}
CAGradientLayer
仅支持轴向(方向性)渐变。 - David Rönnqvist