UIScrollView 两边渐变效果

在继承自UIScrollView的类的layoutSubViews中设置

- (void)layoutSubviews {

[super layoutSubviews];

NSObject *transparent = (NSObject*) [[UIColor colorWithWhite:0 alpha:0] CGColor];

NSObject *opaque = (NSObject*) [[UIColorcolorWithWhite:0 alpha:1] CGColor];

CALayer *maskLayer = [CALayer layer];

maskLayer.frame=self.bounds;

CAGradientLayer *gradientLayer = [CAGradientLayer layer];

gradientLayer.frame= maskLayer.bounds;

gradientLayer.colors=@[transparent, transparent, opaque, opaque, transparent, transparent];

CGFloatpercent1 =2.0/self.bounds.size.width;

CGFloatpercent2 =12.0/self.bounds.size.width;

gradientLayer.locations=@[@(0),@(percent1),@(percent2),@(1- percent2),@(1- percent1),@(1)];

gradientLayer.startPoint=CGPointMake(0,0.5);

gradientLayer.endPoint=CGPointMake(1,0.5);

[maskLayer addSublayer:gradientLayer];

self.layer.mask= maskLayer;

}