Question

我正在尝试滚动到位于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，当textView.selectedRange位于子字符串范围之下时，我只能将子字符串转到顶部。我怎样才能使子串总是出现在顶部，无论以前滚动范围在哪里？

这是我目前的代码

   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?
   }

Answer 1

UITextView是UIScrollView子类，因此如果您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），那么您可以设置contentOffset因此。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)
}

Textview scrollRangeToVisible使范围转到顶部

1 个答案: