iOS AutoLayout Keyboard Adjuster

KeyboardAdjuster.h

@import UIKit;

typedef void (^KeyboardAdjustingBlock)();

@interface KeyboardAdjuster : NSObject

@property (nonatomic, assign) BOOL activated;

@property (nonatomic, nullable, weak) IBOutlet UIView *targetView;
@property (nonatomic, nullable, weak) IBOutlet NSLayoutConstraint *targetConstraint;


+ (nonnull instancetype)createWithView:(nonnull UIView *)view constraint:(nonnull NSLayoutConstraint *)constraint;
- (nonnull instancetype)initWithShow:(nullable KeyboardAdjustingBlock)show hide:(nullable KeyboardAdjustingBlock)hide NS_DESIGNATED_INITIALIZER;

@end

KeyboardAdjuster.m

#import "KeyboardAdjuster.h"

#define SAFE_RUN(block, ...) block ? block(__VA_ARGS__) : nil

@interface KeyboardAdjuster ()

@property (nonatomic, assign) CGFloat advance;
@property (nonatomic, assign) BOOL keyboardOnScreen;

@end

@implementation KeyboardAdjuster

#pragma mark - Initialization

+ (instancetype)createWithView:(UIView *)view constraint:(NSLayoutConstraint *)constraint
{
    KeyboardAdjuster *obj = [KeyboardAdjuster new];
    obj.targetView = view;
    obj.targetConstraint = constraint;
    return obj;
}


- (instancetype)init
{
    return [self initWithShow:nil hide:nil];
}


- (instancetype)initWithShow:(KeyboardAdjustingBlock)show hide:(KeyboardAdjustingBlock)hide
{
    if( self = [super init] ) {
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardStateChange:) name:UIKeyboardWillShowNotification object:show];
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardStateChange:) name:UIKeyboardWillHideNotification object:hide];
    }
    
    return self;
}

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

#pragma mark - Notification handler

- (void)keyboardStateChange:(NSNotification *)evt
{
    if( !self.activated ) {
        return;
    }
    
    KeyboardAdjustingBlock block = evt.object;
    SAFE_RUN(block);
    
    NSDictionary *userInfo = evt.userInfo;
    
    CGRect keyboardFrame = [userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue];
    CGRect viewFrame = [self.targetView convertRect:self.targetView.bounds toView:self.targetView.window];
    
    if( [evt.name isEqualToString:UIKeyboardWillShowNotification] && !self.keyboardOnScreen ) {
        self.keyboardOnScreen = YES;
        CGRect intersection = CGRectIntersection(viewFrame, keyboardFrame);
        
        self.advance = intersection.size.height;
        self.targetConstraint.constant += self.advance;
        
    } else if( [evt.name isEqualToString:UIKeyboardWillHideNotification] ) {
        self.keyboardOnScreen = NO;
        self.targetConstraint.constant -= self.advance;
        self.advance = 0.0;
    }
    
    NSTimeInterval duration = [userInfo[UIKeyboardAnimationDurationUserInfoKey] doubleValue];
    UIViewAnimationCurve curve = [userInfo[UIKeyboardAnimationCurveUserInfoKey] integerValue];
    UIViewAnimationOptions options = UIViewAnimationOptionBeginFromCurrentState | UIViewAnimationOptionLayoutSubviews | curve;
    
    [UIView animateWithDuration:duration delay:0 options:options animations:^{
        [self.targetView.superview setNeedsLayout];
        [self.targetView.superview layoutIfNeeded];
    } completion:nil];
}

@end