关于隐藏键盘

Question

我的问题是：    当我写一个用户登录UI时，因为键盘隐藏了密码文本字段，所以我写了一些代码来向上滚动登录界面，但是当键盘被隐藏并且UI滚动到旧位置时，我发现我触摸了文本字段我无法得到任何回应。

注册通知：

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

_username.delegate = self;
_password.delegate = self;

将显示键盘代码：

- (void) keyboardWillshow:(NSNotification *)noti
 {
    NSDictionary *userInfo = [noti userInfo];
    NSValue *keyValue = [userInfo objectForKey:UIKeyboardFrameEndUserInfoKey];
    CGRect keyboardRect = [keyValue CGRectValue];
    int height = keyboardRect.size.height;
    userInfo = nil;
    keyValue = nil;
    [UIView animateWithDuration:0.5f animations:^{
    self.containView.frame = CGRectMake(0, -height+20, WIDTH/2, HEIGHT/2-20);
    }];
}

将隐藏键盘代码：

- (void)keyboardWillhide:(NSNotification *)noti
{
    [UIView animateWithDuration:0.5f animations:^{
        self.containView.frame = CGRectMake(0, 20, WIDTH/2, HEIGHT/2-20);
    }];
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    [_password resignFirstResponder];
    [_username resignFirstResponder];
}

有人可以帮助我吗？我使用故事板编写代码。