关于UITextView contentSize.height 不正确问题

直接上代码

    CGFloat height=0;

    if ([[[UIDevice currentDevice] systemVersion] floatValue] >= 7) {

        height =ceilf([myTextViewsizeThatFits:myTextView.frame.size].height);

    }else{

        height =myTextView.contentSize.height;

    }