iOS7 UITextView 光标问题

最近在项目中遇到UITextView在ios7上出现编辑进入最后一行时光标消失，看不到最后一行，变成盲打，stackOverFlow网站上有大神指出，是ios7本身bug，加上下面一段代码即可：

-(void)textViewDidChange:(UITextView *)textView {
    CGRect line = [textView caretRectForPosition:
                   textView.selectedTextRange.start];
    CGFloat overflow = line.origin.y + line.size.height
    - ( textView.contentOffset.y + textView.bounds.size.height
       - textView.contentInset.bottom - textView.contentInset.top );
    if ( overflow > 0 ) {
        // We are at the bottom of the visible text and introduced a line feed, scroll down (iOS 7 does not do it)
        // Scroll caret to visible area
        CGPoint offset = textView.contentOffset;
        offset.y += overflow + 7; // leave 7 pixels margin
        // Cannot animate with setContentOffset:animated: or caret will not appear
        [UIView animateWithDuration:.2 animations:^{
            [textView setContentOffset:offset];
        }];
    }
}