Fade edges UIScrollView

FadeScrollView.h

#import <UIKit/UIKit.h>

@interface SNFadeScrollView : UIScrollView

@property (nonatomic) BOOL fadeTop;
@property (nonatomic) BOOL fadeBottom;

@end

FadeScrollView.m

#import <QuartzCore/QuartzCore.h>
#import "SNFadeScrollView.h"

@implementation SNFadeScrollView

- (id)initWithFrame:(CGRect)frame{
    if(self = [super initWithFrame:frame]){
        _fadeTop = YES;
        _fadeBottom = YES;
    }
    return self;
}

- (id)initWithCoder:(NSCoder *)aDecoder{
    if(self = [super initWithCoder:aDecoder]){
        _fadeTop = YES;
        _fadeBottom = YES;
    }
    return self;
}

- (void)setFadeTop:(BOOL)fadeTop{
    if(_fadeTop != fadeTop){
        _fadeTop = fadeTop;
        [self layoutSubviews];
    }
}

- (void)setFadeBottom:(BOOL)fadeBottom{
    if(_fadeBottom != fadeBottom){
        _fadeBottom = fadeBottom;
        [self layoutSubviews];
    }
}

- (void)layoutSubviews{
    if(self.fadeTop || self.fadeBottom){
        CGFloat fadeHeight = SCROLLVIEW_EDGE_FADE;
        
        CALayer *maskLayer = [CALayer layer];
        maskLayer.frame = self.bounds;
        
        CALayer *solidLayer = [CALayer layer];
        solidLayer.backgroundColor = [[UIColor blackColor] CGColor];
        CGRect solidRect = CGRectZero;
        solidRect.origin.x = self.contentOffset.x;
        solidRect.size = self.bounds.size;
        if(self.fadeTop){
            solidRect.origin.y = fadeHeight;
        }
        if(self.fadeBottom){
            solidRect.size.height -= solidRect.origin.y+fadeHeight;
        }
        solidLayer.frame = solidRect;
        [maskLayer addSublayer:solidLayer];
        
        if(self.fadeTop){
            CAGradientLayer *topLayer = [CAGradientLayer layer];
            topLayer.frame = CGRectMake(self.contentOffset.x, 0, self.bounds.size.width, fadeHeight);
            topLayer.colors = @[(id)[[UIColor clearColor] CGColor], (id)[[UIColor blackColor] CGColor]];
            topLayer.startPoint = CGPointZero;
            topLayer.endPoint = CGPointMake(0, 1);
            [maskLayer addSublayer:topLayer];
        }
        
        if(self.fadeBottom){
            CAGradientLayer *bottomLayer = [CAGradientLayer layer];
            bottomLayer.frame = CGRectMake(self.contentOffset.x, self.bounds.size.height-fadeHeight, self.bounds.size.width, fadeHeight);
            bottomLayer.colors = @[(id)[[UIColor blackColor] CGColor], (id)[[UIColor clearColor] CGColor]];
            bottomLayer.startPoint = CGPointZero;
            bottomLayer.endPoint = CGPointMake(0, 1);
            [maskLayer addSublayer:bottomLayer];
        }
        
        self.layer.mask = maskLayer;
    }else{
        self.layer.mask = nil;
    }
}

@end