我如何知道用户何时到达NSTextView中的文本结尾

Question

My users are reading readonly text in a UITextView . When they have finished reading a selection, I would like to be able to display a Completed Reading button. How can I detect when the user has scrolled to the end of the text?

Answer 1

Try this. First before each read calculate the size of the text in the textview based upon the size of its widt. Then from there check if the content offset of the textview has reached the size of the maxSize of the text that was loaded in the text view.

Answer 2

Try this:

float scrollerPosition = [[[textView superview] verticalScroller] floatValue];

The scroller position should be between 0.0 and 1.0 .

Answer 3

I don't think it's right to consult the vertical scroller's position. What happens if the scroll view is large to enough to show the whole text view without scrolling? Is the scroller at 0.0 or 1.0?

I think you should consult the scroll view's -documentVisibleRect and compare it to the text view's -bounds . If the NSMaxY() of the former is greater than or equal to the NSMaxY() of the latter, then the text view's bottom is visible. If the text view might also scroll horizontally and you care if they scrolled all the way to the right, also check the NSMaxX() of both rects in the same way.