给UIView控件换成渐变色

需求：给UIView控件换成渐变色（UILabel、UIButton、UIView）

#pragma mark view添加字体渐变色
+ (UIColor *)addGradientToView:(UIView *)view withColorArr:(NSArray *)colorArr
{
    UIGraphicsBeginImageContextWithOptions(view.bounds.size, NO, [UIScreen mainScreen].scale);
    CGContextRef context = UIGraphicsGetCurrentContext();
    //绘制渐变层
    CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
    CGGradientRef gradientRef = CGGradientCreateWithColors(colorSpaceRef,
                                                           (__bridge CFArrayRef)colorArr,
                                                           NULL);
    CGPoint startPoint = CGPointZero;
    CGPoint endPoint = CGPointMake(CGRectGetMaxX(view.bounds), CGRectGetMaxY(view.bounds));
    CGContextDrawLinearGradient(context, gradientRef, startPoint, endPoint,  kCGGradientDrawsBeforeStartLocation | kCGGradientDrawsAfterEndLocation);
    //取到渐变图片
    UIImage *gradientImage = UIGraphicsGetImageFromCurrentImageContext();
    //释放资源
    CGColorSpaceRelease(colorSpaceRef);
    CGGradientRelease(gradientRef);
    UIGraphicsEndImageContext();
    return  [UIColor colorWithPatternImage:gradientImage];
}