Ios text查看滚动范围可见使范围变为顶部

我试图滚动到UITextView的attributedText中的特定子字符串。滚动完成后，我希望子字符串位于可见textview文本的顶部。但是，只有当textView.selectedRange位于子字符串的范围之下时，我才能使子字符串转到顶部。如何使子字符串始终显示在顶部，无论滚动范围以前位于何处

这是我当前的代码

   let text =  // a long NSAttributedString
   let substring = "put me at the top!"
   textView.attributedText = text

   func scrollToSubstring() {
      let str = text.string as NSString

      let range = str.rangeOfString(substring, options: .RegularExpressionSearch, range: NSMakeRange(0, str.length), locale: nil)

      textView.scrollRangeToVisible(range)
      // HOW CAN I MAKE IT SO range ALWAYS APPEARS AT THE TOP?
   }

---

UITextView

是一个

UIScrollView

子类，因此如果可以在滚动视图的坐标中找到子字符串的位置（可以使用

TextKit

），则可以相应地设置

contentOffset

。这对我有用：

func scrollSubstringToTop() {
    let str = text.string as NSString

    let substringRange = str.rangeOfString(substring)
    let glyphRange = textView.layoutManager.glyphRangeForCharacterRange(substringRange, actualCharacterRange: nil)
    let rect = textView.layoutManager.boundingRectForGlyphRange(glyphRange, inTextContainer: textView.textContainer)
    let topTextInset = textView.textContainerInset.top
    let contentOffset = CGPoint(x: 0, y: topTextInset + rect.origin.y)

    textView.setContentOffset(contentOffset, animated: true)
}