获取键盘的y

1.监听键盘

    [[NSNotificationCenter defaultCenter] addObserver:view selector:@selector(keyboardWillShow:) name:UIKeyboardWillShowNotification object:nil];

- (void)keyboardWillShow:(NSNotification *)notification{
    //取得键盘最后的frame
    CGRect keyboardFrame = [notification.userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue];
    CGFloat height = keyboardFrame.origin.y;
    
}