键盘自动消失

Question

键盘消失时我有一点问题，我添加了观察者：

    [[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(keyboardDidDisappear:)
                                             name:UIKeyboardWillHideNotification
                                           object:nil];

添加方法：

- (void) keyboardDidDisappear:(NSNotification *)notification {
    NSLog(@"disappear");
}

在我的应用程序中，我有一些按钮，点击它会显示两个uitextfield这个方法：

    - (void) showFieldStoryView:(id)sender {

    if (storyContentView.hidden == NO) {

        UIButton *button = (UIButton *)sender;
        buttonTag = [button tag];
        int indexArray = buttonTag - 1;

        NSMutableDictionary *dict = [arrayPunteggi objectAtIndex:indexArray];

        [fieldUno removeFromSuperview];
        [fieldDue removeFromSuperview];

        [fieldUno setHidden:YES];
        [fieldDue setHidden:YES];

        [storyContentView addSubview:fieldUno];
        [storyContentView addSubview:fieldDue];

        [fieldUnoAccusi removeFromSuperview];
        [fieldDueAccusi removeFromSuperview];

        [fieldUnoAccusi setHidden:YES];
        [fieldDueAccusi setHidden:YES];

        [labelPunti removeFromSuperview];
        [labelAccusi removeFromSuperview];
        [labelPunti setHidden:YES];
        [labelAccusi setHidden:YES];
        [storyContentView addSubview:labelPunti];
        [storyContentView addSubview:labelAccusi];

        if (fieldUno.isFirstResponder) {
            point = CGPointMake(0,button.frame.origin.y);
        }
        else {
            [fieldUno becomeFirstResponder];
        }
    }
}

问题是，每次我点击这个按钮，我都会在控制台上看到日志消失，奇怪的是，键盘总是显示哦屏幕，问题出在哪里？