UIKeyboardWillChangeFrameNotification method

gistfile1.m

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWillChange:)
                                                 name:UIKeyboardWillChangeFrameNotification
                                               object:nil];
}

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

#pragma mark - keyboard

// abstract
- (void)doKeyboardAnimateTo:(CGFloat)toValue
{
}

// abstract
- (void)completedKeyboardAnimateTo:(CGFloat)toValue
{
}

- (void)keyboardWillChange:(NSNotification *)notification
{
    [self.view layoutIfNeeded];

    NSDictionary* info = notification.userInfo;
    CGRect kbRect = [info[UIKeyboardFrameEndUserInfoKey] CGRectValue];
    CGFloat fromBottom = MAX(0, self.view.frame.size.height - kbRect.origin.y);

    NSValue * animationDurationValue = info[UIKeyboardAnimationDurationUserInfoKey];
    NSTimeInterval duration;
    [animationDurationValue getValue:&duration];

    UIViewAnimationCurve curve = [info[UIKeyboardAnimationCurveUserInfoKey] integerValue];
    UIViewAnimationOptions animOpt;
    switch (curve) {
        case UIViewAnimationCurveEaseInOut:
            animOpt = UIViewAnimationOptionCurveEaseInOut;
            break;

        case UIViewAnimationCurveEaseIn:
            animOpt = UIViewAnimationOptionCurveEaseIn;
            break;

        case UIViewAnimationCurveEaseOut:
            animOpt = UIViewAnimationOptionCurveEaseOut;
            break;

        case UIViewAnimationCurveLinear:
            animOpt = UIViewAnimationOptionCurveLinear;
            break;

        default:
            animOpt = UIViewAnimationOptionCurveEaseInOut;
            break;
    }
    animOpt = animOpt | UIViewAnimationOptionTransitionNone;

    void (^animation)() = ^
    {
        [self doKeyboardAnimateTo:fromBottom];
        [self.view layoutIfNeeded];
    };

    void (^completion)(BOOL) = ^(BOOL fin)
    {
        [self completedKeyboardAnimateTo:fromBottom];
    };

    [UIView animateWithDuration:duration
                          delay:0
                        options:animOpt
                     animations:animation
                     completion:completion];
}