あれ

MainViewController.m

#define ANIMATION_DURATION 0.2f
#define TRIGGER_DELTA 40.0f

@interface MainViewController : UIViewController <UITableViewDataSource, UITableViewDelegate, UITextFieldDelegate>

@end

@implementation MainViewController
{
    UITableView *_tableView;
    UIView *_accessoryView;
    UITextField *_textField;

    CGRect _initialKeyboardFrame;
    CGFloat _maxKeyboardViewY, _minKeyboardViewY;
    CGPoint _initialContentOffset;

    BOOL _isKeyboardDisplayed;

    NSMutableArray *_items;
}

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        _items = [[NSMutableArray alloc] init];
        for (NSUInteger i = 0; i < 30; ++i) {
            [_items addObject:[NSString stringWithFormat:@"Dummy Item %d", i]];
        }

        self.title = @"Keyboard View Test";

        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(_keyboardWillShow:) name:UIKeyboardWillShowNotification object:nil];
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(_keyboardDidShow:) name:UIKeyboardDidShowNotification object:nil];
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(_keyboardWillHide:) name:UIKeyboardWillHideNotification object:nil];
    }
    return self;
}

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

- (UIView *)_keyboardView
{
    return _accessoryView.superview;
}

- (void)_setScrollViewBottomInset:(CGFloat)bottomInset
{
    UIEdgeInsets insets;

    insets = _tableView.contentInset;
    insets.bottom = bottomInset;
    _tableView.contentInset = insets;

    insets = _tableView.scrollIndicatorInsets;
    insets.bottom = bottomInset;
    _tableView.scrollIndicatorInsets = insets;
}

#pragma UIViewController

- (void)loadView
{
    [super loadView];

    _tableView = [[UITableView alloc] initWithFrame:self.view.bounds];
    _tableView.delegate = self;
    _tableView.dataSource = self;
    [self.view addSubview:_tableView];

    _accessoryView = [[UIView alloc] initWithFrame:CGRectMake(0.0f, 0.0f, self.view.bounds.size.width, 40.0f)];
    _accessoryView.backgroundColor = [UIColor lightGrayColor];
    _accessoryView.autoresizingMask = UIViewAutoresizingFlexibleWidth;

    _textField = [[UITextField alloc] initWithFrame:_accessoryView.bounds];
    _textField.autoresizingMask = UIViewAutoresizingFlexibleWidth;
    _textField.delegate = self;
    [_accessoryView addSubview:_textField];

    UITextField *textField = [[UITextField alloc] initWithFrame:CGRectZero];
    textField.hidden = YES;
    textField.inputAccessoryView = _accessoryView;
    [self.view addSubview:textField];
    [textField becomeFirstResponder];
}

- (UIInterfaceOrientation)preferredInterfaceOrientationForPresentation
{
    return UIInterfaceOrientationPortrait;
}

#pragma mark Notifications

- (void)_keyboardWillShow:(NSNotification *)notification
{
    NSDictionary* userInfo = [notification userInfo];

    CGRect frame = [[userInfo objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];
    NSNumber* duration = userInfo[UIKeyboardAnimationDurationUserInfoKey];
    UIViewAnimationCurve animationCurve = [userInfo[UIKeyboardAnimationCurveUserInfoKey] unsignedIntegerValue];

    [UIView animateWithDuration:[duration doubleValue] animations:^{
        [UIView setAnimationCurve:animationCurve];
        [self _setScrollViewBottomInset:frame.size.height];
    }];
}

- (void)_keyboardDidShow:(NSNotification *)notification
{
    CGRect frame = [self _keyboardView].frame;
    _minKeyboardViewY = CGRectGetMinY(frame);
    _maxKeyboardViewY = CGRectGetMaxY(frame) - _accessoryView.frame.size.height;
    [_textField becomeFirstResponder];

    _isKeyboardDisplayed = YES;
}

- (void)_keyboardWillHide:(NSNotification *)notification
{
    _isKeyboardDisplayed = NO;
}

#pragma mark UITableViewDelegate

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
    if (!_isKeyboardDisplayed) {
        return;
    }

    _initialKeyboardFrame = [self _keyboardView].frame;
    _initialContentOffset = scrollView.contentOffset;
}

- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    if (!_isKeyboardDisplayed || !scrollView.tracking) {
        return;
    }

    UIView *keyboardView = _accessoryView.superview;
    CGFloat delta = scrollView.contentOffset.y - _initialContentOffset.y;

    CGRect frame = _initialKeyboardFrame;
    CGFloat y = fminf(fmaxf(frame.origin.y - delta, _minKeyboardViewY), _maxKeyboardViewY);
    if (y != frame.origin.y) {
        frame.origin.y = y;
        keyboardView.frame = frame;
    }
}

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{
    if (!_isKeyboardDisplayed) {
        return;
    }

    UIView *keyboardView = _accessoryView.superview;
    CGRect frame = keyboardView.frame;

    CGFloat delta =  frame.origin.y - _initialKeyboardFrame.origin.y;
    if (delta > TRIGGER_DELTA) {
        frame.origin.y = _maxKeyboardViewY;
    } else if (delta < -TRIGGER_DELTA) {
        frame.origin.y = _minKeyboardViewY;
    } else {
        frame = _initialKeyboardFrame;
    }

    [UIView animateWithDuration:ANIMATION_DURATION animations:^{
        keyboardView.frame = frame;
        // FIXME assuming the view and keyboard view is using same corrdinate.
        // These are not on the same window.
        [self _setScrollViewBottomInset:(self.view.bounds.size.height - frame.origin.y)];
    }];
}


#pragma mark UITableViewDataSource

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"cell"];
    if (!cell) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"cell"];
        cell.selectionStyle = UITableViewCellSelectionStyleNone;
    }
    cell.textLabel.text = [_items objectAtIndex:indexPath.row];
    return cell;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return [_items count];
}

#pragma mark UITextFieldDelegate

- (BOOL)textFieldShouldReturn:(UITextField *)textField
{
    [self _addText:textField.text];
    textField.text = @"";
    return NO;
}

- (void)_addText:(NSString *)text
{
    [_items addObject:[NSString stringWithString:text]];
    [_tableView reloadData];
    NSUInteger row = [_items count] - 1;
    [_tableView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:row inSection:0] atScrollPosition:UITableViewScrollPositionBottom animated:YES];
}

@end