如何在iOS应用程序中创建内联文本锚点

Question

I have a simple iOS app that dynamically loads content with HTML styling into a UITextView .

This works great as NSAttributedString handles all the HTML tags that I need to be able to support, with the exception of one case, which is for inline text anchors. It handles external links just fine, but doesn't appear to either recognise or jump to text anchors when tapped.

For example, if I supply the view with the following HTML (converted to an NSAttributedString ):

<p><a href="#anchor1">Lorem ipsum</a> dolor sit amet, consectetur adipiscing elit. Fusce dapibus, ante et varius imperdiet, est risus tincidunt ex, non fermentum enim eros quis metus. Quisque vehicula lacus at ornare ullamcorper. Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Integer scelerisque lectus quis libero rutrum, quis condimentum dolor porta.</p>

[lots more text]

<p><a name="anchor1">Sed</a> eros purus, lobortis a rhoncus id, facilisis ac orci. In hac habitasse platea dictumst. In sagittis in orci vitae volutpat. Quisque sollicitudin lectus at est ultrices, et volutpat diam lobortis.</p>

Clicking the Lorem ipsum link does nothing in this case, but if I change its href to some external URL then that triggers as expected, so the issue appears to be internal links only.

So what I'm wondering is, is it possible to natively use HTML style named anchors within UITextView at all? If not, are there any simple alternatives?

I'm using Swift, so an answer in that language (if coding is necessary) is preferred.

Answer 1

I am not aware of any HTML - JS only based solution.

But there is something similar I did in one if my apps except that I did not scroll to a particular section of textview. There is a delegate of UITextView that gives you handle on which url was clicked.

You can use this to get the url. The next problem is to get the scroll offset of that anchor tag in the whole text. Of the top of my mind, one way to get that info is search the text for the anchor tag then using a NSString method like this to get the height that the string would require. Use that as the scroll offset.

Clearly, doing this computation on the main thread after the user clicks the link will be a very bad user experience. Hence, you can pre-compute this height if you architect your app in an appropriate way.