监听键盘弹出高度

- (void)registerForKeyboardNotifications
{
//使用NSNotificationCenter 鍵盤出現時
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(keyboardWillShown:)
name:UIKeyboardWillChangeFrameNotification object:nil];
//使用NSNotificationCenter 鍵盤隐藏時
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(keyboardWillBeHidden:)
name:UIKeyboardWillHideNotification object:nil];
}

//实现当键盘出现的时候计算键盘的高度大小。用于输入框显示位置
- (void)keyboardWillShown:(NSNotification*)aNotification
{

NSDictionary *info = [notification userInfo];

    CGFloat duration = [[info objectForKey:UIKeyboardAnimationDurationUserInfoKey] floatValue];

    NSValue *value = [info objectForKey:UIKeyboardFrameEndUserInfoKey];

    CGSize keyboardSize = [value CGRectValue].size;

//输入框位置动画加载

    [UIView animateWithDuration:duration animations:^{

//do something

    }];

}

//当键盘隐藏的时候- (void)keyboardWillBeHidden:(NSNotification*)aNotification{ //do something}