我试图在运行时生成一个渐变颜色背景(纯色到透明)的视图。有办法做到吗?
当前回答
在Swift 3.1中 我已经添加了这个扩展到UIView
import Foundation
import UIKit
import CoreGraphics
extension UIView {
func gradientOfView(withColours: UIColor...) {
var cgColours = [CGColor]()
for colour in withColours {
cgColours.append(colour.cgColor)
}
let grad = CAGradientLayer()
grad.frame = self.bounds
grad.colors = cgColours
self.layer.insertSublayer(grad, at: 0)
}
}
然后我用它来调用
class OverviewVC: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
self.view.gradientOfView(withColours: UIColor.red,UIColor.green, UIColor.blue)
}
}
其他回答
这是我推荐的方法。
为了提高可重用性,我建议创建一个CAGradientLayer类别,并添加所需的渐变作为类方法。在头文件中像这样指定它们:
#import <QuartzCore/QuartzCore.h>
@interface CAGradientLayer (SJSGradients)
+ (CAGradientLayer *)redGradientLayer;
+ (CAGradientLayer *)blueGradientLayer;
+ (CAGradientLayer *)turquoiseGradientLayer;
+ (CAGradientLayer *)flavescentGradientLayer;
+ (CAGradientLayer *)whiteGradientLayer;
+ (CAGradientLayer *)chocolateGradientLayer;
+ (CAGradientLayer *)tangerineGradientLayer;
+ (CAGradientLayer *)pastelBlueGradientLayer;
+ (CAGradientLayer *)yellowGradientLayer;
+ (CAGradientLayer *)purpleGradientLayer;
+ (CAGradientLayer *)greenGradientLayer;
@end
然后在你的实现文件中,用下面的语法指定每个渐变:
+ (CAGradientLayer *)flavescentGradientLayer
{
UIColor *topColor = [UIColor colorWithRed:1 green:0.92 blue:0.56 alpha:1];
UIColor *bottomColor = [UIColor colorWithRed:0.18 green:0.18 blue:0.18 alpha:1];
NSArray *gradientColors = [NSArray arrayWithObjects:(id)topColor.CGColor, (id)bottomColor.CGColor, nil];
NSArray *gradientLocations = [NSArray arrayWithObjects:[NSNumber numberWithInt:0.0],[NSNumber numberWithInt:1.0], nil];
CAGradientLayer *gradientLayer = [CAGradientLayer layer];
gradientLayer.colors = gradientColors;
gradientLayer.locations = gradientLocations;
return gradientLayer;
}
然后简单地将这个类别导入你的ViewController或任何其他所需的子类,并像这样使用它:
CAGradientLayer *backgroundLayer = [CAGradientLayer purpleGradientLayer];
backgroundLayer.frame = self.view.frame;
[self.view.layer insertSublayer:backgroundLayer atIndex:0];
调用上面的解决方案来更新层是一个好主意
viewDidLayoutSubviews
正确地更新视图
你可以创建一个自定义类GradientView:
斯威夫特5
class GradientView: UIView {
override open class var layerClass: AnyClass {
return CAGradientLayer.classForCoder()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
let gradientLayer = layer as! CAGradientLayer
gradientLayer.colors = [UIColor.white.cgColor, UIColor.black.cgColor]
}
}
在故事板中,将类类型设置为你想要有渐变背景的任何视图:
这在以下方面是更好的:
不需要设置框架的克莱尔 像往常一样在UIView上使用NSConstraint 不需要创建子层(更少的内存使用)
试试这个对我来说很有魔力,
Objective - C
我已经设置了RGB渐变背景颜色为UIview
UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0,0,320,35)];
CAGradientLayer *gradient = [CAGradientLayer layer];
gradient.frame = view.bounds;
gradient.startPoint = CGPointZero;
gradient.endPoint = CGPointMake(1, 1);
gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor colorWithRed:34.0/255.0 green:211/255.0 blue:198/255.0 alpha:1.0] CGColor],(id)[[UIColor colorWithRed:145/255.0 green:72.0/255.0 blue:203/255.0 alpha:1.0] CGColor], nil];
[view.layer addSublayer:gradient];
更新: Swift3 +
代码:
var gradientView = UIView(frame: CGRect(x: 0, y: 0, width: 320, height: 35))
let gradientLayer:CAGradientLayer = CAGradientLayer()
gradientLayer.frame.size = self.gradientView.frame.size
gradientLayer.colors =
[UIColor.white.cgColor,UIColor.red.withAlphaComponent(1).cgColor]
//Use diffrent colors
gradientView.layer.addSublayer(gradientLayer)
你可以添加渐变颜色的起点和终点。
gradientLayer.startPoint = CGPoint(x: 0.0, y: 1.0)
gradientLayer.endPoint = CGPoint(x: 1.0, y: 1.0)
更多细节请参考CAGradientLayer文档
希望这对一些人有所帮助。
我已经在swift中实现了一个扩展:
斯威夫特3
extension UIView {
func addGradientWithColor(color: UIColor) {
let gradient = CAGradientLayer()
gradient.frame = self.bounds
gradient.colors = [UIColor.clear.cgColor, color.cgColor]
self.layer.insertSublayer(gradient, at: 0)
}
}
斯威夫特2.2
extension UIView {
func addGradientWithColor(color: UIColor) {
let gradient = CAGradientLayer()
gradient.frame = self.bounds
gradient.colors = [UIColor.clearColor().CGColor, color.CGColor]
self.layer.insertSublayer(gradient, atIndex: 0)
}
}
不,我可以像这样在每个视图上设置渐变:
myImageView.addGradientWithColor(UIColor.blue)
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