UITextView自适应高度

currentLineNum = 1;//默认文本框显示一行文字
NSDictionary *dict=@{NSFontAttributeName:[UIFont systemFontOfSize:14.0]};
CGSize contentSize=[@"我" sizeWithAttributes:dict];
heightText = contentSize.height;

self.textView.font = [UIFont systemFontOfSize:14.0];
self.textView.textContainerInset = UIEdgeInsetsZero;
self.textView.textContainer.lineFragmentPadding = 0;
self.textView.delegate = self;

#pragma mark - UITextViewDelegate
- (void)textViewDidChange:(UITextView *)textView{
    float textViewWidth = self.textView.frame.size.width;//取得文本框高度
    NSString *content = textView.text;
    NSDictionary *dict = @{NSFontAttributeName:[UIFont systemFontOfSize:14.0]};
    CGSize contentSize = [content sizeWithAttributes:dict];//计算文字长度
    float numLine = ceilf(contentSize.width/textViewWidth);
    if(numLine > currentLineNum ){
        //如果发现当前文字长度对应的行数超过。 文本框高度，则先调整当前view的高度和位置，然后调整输入框的高度，最后修改currentLineNum的值
        self.layoutViewTextHeight.constant = self.textView.frame.size.height+heightText*(numLine-currentLineNum) + 28.0;
        currentLineNum = numLine;

   }else if (numLine < currentLineNum ){
       //次数为删除的时候检测文字行数减少的时候
       if (numLine <= 1) {
           self.layoutViewTextHeight.constant = 48.0;
       }else {
           self.layoutViewTextHeight.constant = self.textView.frame.size.height-heightText*(currentLineNum-numLine) + 28.0;
       }
    }
    
    if (numLine == 0) {
        numLine = 1;
    }
    currentLineNum = numLine;
}

- (void)scrollViewDidScroll:(UIScrollView*)scrollView {
    // 防止换行时抖动
    scrollView.contentOffset = CGPointZero;
}