UIViewController Keyboard Management

gistfile1.txt

@interface ViewController : UIViewController

@property (nonatomic, readonly, nullable) UIView *keyboardAnchorView;
@property (nonatomic, readonly, nullable) NSLayoutConstraint *keyboardAnchorViewHeightConstraint;

@end


@implementation

- (void)viewDidLoad {
    _keyboardAnchorView = [UIView new];
    [self.view addSubview:_keyboardAnchorView];
    [_keyboardAnchorView autoPinEdgesToSuperviewEdgesWithInsets:UIEdgeInsetsZero excludingEdge:ALEdgeTop];
    _keyboardAnchorViewHeightConstraint = [_keyboardAnchorView autoSetDimension:ALDimensionHeight toSize:0];
}

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillShow:) name:UIKeyboardWillShowNotification object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillHide:) name:UIKeyboardWillHideNotification object:nil];
}

- (void)viewWillDisappear:(BOOL)animated {
    [super viewWillDisappear:animated];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillShowNotification object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillHideNotification object:nil];
}

- (void)keyboardWillShow:(NSNotification *)notification {
    CGRect keyboardRect = [notification.userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue];
    keyboardRect = [self.view convertRect:keyboardRect fromView:[[UIApplication sharedApplication] keyWindow]];

    _keyboardAnchorViewHeightConstraint.constant = CGRectGetHeight(self.view.bounds) - keyboardRect.origin.y;

    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationDuration:[notification.userInfo[UIKeyboardAnimationDurationUserInfoKey] doubleValue]];
    [UIView setAnimationCurve:[notification.userInfo[UIKeyboardAnimationCurveUserInfoKey] integerValue]];
    [UIView setAnimationBeginsFromCurrentState:YES];

    [self.view layoutIfNeeded];
    [[NSNotificationCenter defaultCenter] postNotificationName:ViewControllerKeyboardAnchorViewDidChangeNotification object:self];

    [UIView commitAnimations];
}

- (void)keyboardWillHide:(NSNotification *)notification {
    _keyboardAnchorViewHeightConstraint.constant = 0;

    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationDuration:[notification.userInfo[UIKeyboardAnimationDurationUserInfoKey] doubleValue]];
    [UIView setAnimationCurve:[notification.userInfo[UIKeyboardAnimationCurveUserInfoKey] integerValue]];
    [UIView setAnimationBeginsFromCurrentState:YES];

    [self.view layoutIfNeeded];
    [[NSNotificationCenter defaultCenter] postNotificationName:ViewControllerKeyboardAnchorViewDidChangeNotification object:self];

    [UIView commitAnimations];
}

@end