Keyboard and ScrollView behaviour example

KeyboardAndScrollViewController.m

@interface KeyboardAndScrollViewController ()
    @property (weak, nonatomic) IBOutlet UIScrollView *scrollView;
    @property (weak, nonatomic) IBOutlet NSLayoutConstraint *scrollViewBottomConstraint;
@end
    
@implementation KeyboardAndScrollViewController
    
- (void)viewDidLoad {
    [super viewDidLoad];

    self.title = @"";

    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardBecameVisible:) name:UIKeyboardWillShowNotification object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWentAway:) name:UIKeyboardWillHideNotification object:nil];
}

- (void)keyboardBecameVisible:(NSNotification *)notification {
    NSLog(@"Keyboard became visible");

    // if we have no view or are not visible in any window, we don't care
    if (!self.isViewLoaded || !self.view.window) {
        return;
    }

    NSDictionary *userInfo = [notification userInfo];

    CGRect keyboardFrameInWindow;
    [[userInfo objectForKey:UIKeyboardFrameEndUserInfoKey] getValue:&keyboardFrameInWindow];

    // the keyboard frame is specified in window-level coordinates. this calculates the frame as if it were a subview of our view, making it a sibling of the scroll view
    CGRect keyboardFrameInView = [self.view convertRect:keyboardFrameInWindow fromView:nil];

    float keyboardHeight = keyboardFrameInView.size.height;
    NSLog([NSString stringWithFormat:@"KeyboardHeight=%f", keyboardHeight]);

    [self.scrollView setNeedsUpdateConstraints];
    [self.scrollViewBottomConstraint setConstant:keyboardHeight * -1.f];
    [self.view setNeedsLayout];
    [self.view layoutIfNeeded];
}

- (void)keyboardWentAway:(NSNotification *)notification {
    NSLog(@"Keyboard went away");

    // if we have no view or are not visible in any window, we don't care
    if (!self.isViewLoaded || !self.view.window) {
        return;
    }

    [self.scrollView setNeedsUpdateConstraints];
    [self.scrollViewBottomConstraint setConstant:0];
    [self.view setNeedsLayout];
    [self.view layoutIfNeeded];
}

- (void)dealloc
{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}
    
@end