FadingScrollView.m

//
//  YMMFadingScrollView.m
//  Youmiam
//
//  Created by Lukas on 4/14/14.
//  Copyright (c) 2014 Siu. All rights reserved.
//

#import "YMMFadingScrollView.h"

@implementation YMMFadingScrollView

static CGFloat const kFadePercentage = 0.1f;
static CGFloat const kScrollBarWidth = 7;

- (void)layoutSubviews
{
    [super layoutSubviews];
    
    NSObject * transparent = (NSObject *) [[UIColor colorWithWhite:0 alpha:0] CGColor];
    NSObject * opaque = (NSObject *) [[UIColor colorWithWhite:0 alpha:1] CGColor];
    
    CALayer * maskLayer = [CALayer layer];
    maskLayer.frame = self.bounds;
    
    CALayer * scrollGutterLayer = [CALayer layer];
    scrollGutterLayer.frame = CGRectMake(self.bounds.size.width - kScrollBarWidth, 0,
                                         kScrollBarWidth, self.bounds.size.height);
    scrollGutterLayer.backgroundColor = (__bridge CGColorRef)(opaque);
    
    CAGradientLayer * gradientLayer = [CAGradientLayer layer];
    gradientLayer.frame = CGRectMake(self.bounds.origin.x, 0,
                                     self.bounds.size.width, self.bounds.size.height);
    
    gradientLayer.colors = [NSArray arrayWithObjects: transparent, opaque,
                            opaque, transparent, nil];
    
    // Set percentage of scrollview that fades at top & bottom
    gradientLayer.locations = [NSArray arrayWithObjects:
                               [NSNumber numberWithFloat:0],
                               [NSNumber numberWithFloat:kFadePercentage],
                               [NSNumber numberWithFloat:1.0 - kFadePercentage],
                               [NSNumber numberWithFloat:1], nil];
    
    
//    gradientLayer.colors = [NSArray arrayWithObjects: opaque, transparent, nil];
//    
//    gradientLayer.locations = [NSArray arrayWithObjects:[NSNumber numberWithFloat:1.0 -     kFadePercentage], [NSNumber numberWithFloat:1], nil];
    
    gradientLayer.startPoint=CGPointMake(0.5, 0);
    gradientLayer.endPoint=CGPointMake(0.5, 1);
    
    [maskLayer addSublayer:gradientLayer];
    [maskLayer addSublayer:scrollGutterLayer];
    self.layer.mask = maskLayer;
}

@end