iOS textViewDidChange 中用attributedText 导致输入中文的问题

-(void)textViewDidChange:(UITextView *)textView{

NSMutableAttributedString *str = [[NSMutableAttributedString alloc] initWithString:_contentTxtView.text];
[str addAttribute:NSForegroundColorAttributeName value:Content_Color range:NSMakeRange(0,_contentTxtView.text.length)];
[str addAttribute:NSFontAttributeName value:Content_Font range:NSMakeRange(0, _contentTxtView.text.length)];
_contentTxtView.attributedText = str;
}

http://segmentfault.com/q/1010000004133510

没明白。。导致输入中文是什么意思