IOS 动态获取键盘高度

    //增加监听，当键盘出现或改变时收出消息
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillShow:) name:UIKeyboardWillShowNotification object:nil];
    //增加监听，当键退出时收出消息
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillHide:) name:UIKeyboardWillHideNotification object:nil];
}
- (void)dealloc {
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillShowNotification object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillHideNotification object:nil];
}
#pragma mark - notif

- (void)keyboardWillShow:(NSNotification *)notification
{
    NSDictionary* info = [notification userInfo];
    CGSize kbSize = [[info objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue].size;

    [UIView animateWithDuration:[info[UIKeyboardAnimationDurationUserInfoKey] doubleValue]
                          delay:0
                        options:([info[UIKeyboardAnimationCurveUserInfoKey] integerValue]<<16)
                     animations:^{
                         _tableFooterLayout.constant = 60 + kbSize.height;
                     }
                     completion:nil];
}

- (void)keyboardWillHide:(NSNotification *)notification {
    NSDictionary* info = [notification userInfo];
    [UIView animateWithDuration:[info[UIKeyboardAnimationDurationUserInfoKey] doubleValue]
                          delay:0
                        options:([info[UIKeyboardAnimationCurveUserInfoKey] integerValue]<<16)
                     animations:^{
                         _tableFooterLayout.constant = 60;
                     }
                     completion:nil];
}