UIScrollView+KeyboardInsets.h

#import <UIKit/UIKit.h>

@interface UIScrollView (KeyboardInsets)
- (void)addInsetsForKeyboardHandlers;
- (void)removeInsetsForKeyboardHandlers;

@end

UIScrollView+KeyboardInsets.m

#import "UIScrollView+KeyboardInsets.h"
#import <objc/runtime.h>

@implementation UIScrollView (KeyboardInsets)

#pragma mark - Public Interface
- (void)addInsetsForKeyboardHandlers
{
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(updateInsetsForKeyboardWillHideNotification:) name:UIKeyboardWillHideNotification object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(updateInsetsForKeyboardWillShowNotification:) name:UIKeyboardWillShowNotification object:nil];
}

- (void)removeInsetsForKeyboardHandlers
{
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillHideNotification object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillShowNotification object:nil];
}


#pragma mark - Private
- (void)setSavedScrollInsets:(UIEdgeInsets)insets
{
    NSValue *insetsValue = [NSValue valueWithUIEdgeInsets:insets];
    objc_setAssociatedObject(self, @selector(savedScrollInsets), insetsValue, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (UIEdgeInsets)savedScrollInsets
{
    NSValue *insetsValue = objc_getAssociatedObject(self, @selector(savedScrollInsets));
    UIEdgeInsets insets = UIEdgeInsetsZero;
    
    if (insetsValue)
    {
        insets = [insetsValue UIEdgeInsetsValue];
    }
    
    return insets;
}

- (void)setHasSavedScrollInsets:(BOOL)hasSaved
{
    NSNumber *hasSavedNumber = [NSNumber numberWithBool:hasSaved];
    objc_setAssociatedObject(self, @selector(hasSavedScrollInsets), hasSavedNumber, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (BOOL)hasSavedScrollInsets
{
    NSNumber *hasSavedScrollInsets = objc_getAssociatedObject(self, @selector(hasSavedScrollInsets));
    return [hasSavedScrollInsets boolValue];
}

- (void)updateInsetsForKeyboardWillShowNotification:(NSNotification *)notification
{
    if (![self hasSavedScrollInsets])
    {
        [self setSavedScrollInsets:[self contentInset]];
        [self setHasSavedScrollInsets:YES];
    }
    
    
    NSDictionary *userInfo = [notification userInfo];
    NSTimeInterval animationDuration = [userInfo[UIKeyboardAnimationDurationUserInfoKey] doubleValue];
    UIViewAnimationOptions animationOptions = [userInfo[UIKeyboardAnimationCurveUserInfoKey] unsignedIntegerValue];
    CGRect endingFrame = [userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue];
    CGRect convertedFromView = [self convertRect:endingFrame fromView:nil];
    CGFloat height = CGRectGetHeight(self.frame) - CGRectGetMinY(convertedFromView) + [self contentOffset].y;
    
    UIEdgeInsets insets = UIEdgeInsetsMake(0.0, 0.0, height, 0.0);
    
    [UIView animateWithDuration:animationDuration delay:0.0 options:animationOptions animations:^{
        
        [self setScrollIndicatorInsets:insets];
        [self setContentInset:insets];
        
    } completion:nil];
}

- (void)updateInsetsForKeyboardWillHideNotification:(NSNotification *)notification
{
    NSDictionary *userInfo = [notification userInfo];
    NSTimeInterval animationDuration = [userInfo[UIKeyboardAnimationDurationUserInfoKey] doubleValue];
    UIViewAnimationOptions animationOptions = [userInfo[UIKeyboardAnimationCurveUserInfoKey] unsignedIntegerValue];
    
    [UIView animateWithDuration:animationDuration delay:0.0 options:animationOptions animations:^{
        
        UIEdgeInsets insets = [self savedScrollInsets];
        [self setScrollIndicatorInsets:insets];
        [self setContentInset:insets];
        [self setHasSavedScrollInsets:NO];
        
    } completion:nil];
}

@end