找一个调和的，

    bottomView.frame = CGRectMake(bottomView.frame.origin.x, self.contentView.frame.size.height - keyboardHeight - contentSize.height - textViewBgAndCursor*2, bottomView.frame.size.width, contentSize.height + textViewBgAndCursor * 2);

#define textViewCursorToTop 1

#define textViewHeightLimit 6

#define textViewBgAndCursor 5