UITextView中光标的像素位置

问题描述

有没有办法在UITextView中获取光标（闪烁条）的位置（CGPoint）（相对于其内容更可取）。我不是说NSRange的位置。我需要一些东西：

Is there a way of getting the position (CGPoint) of the cursor (blinking bar) in an UITextView (preferable relative to its content). I don’t mean the location as an NSRange. I need something around:

- (CGPoint)cursorPosition;

它应该是一种非私有的API方式。

It should be a non-private API way.

推荐答案

这是痛苦的，但你可以使用 UIStringDrawing 补充的NSString 做到这一点。这是我使用的一般算法：

It's painful, but you can use the UIStringDrawing additions to NSString to do it. Here's the general algorithm I used:

CGPoint origin = textView.frame.origin;
NSString* head = [textView.text substringToIndex:textView.selectedRange.location];
CGSize initialSize = [head sizeWithFont:textView.font constrainedToSize:textView.contentSize];
NSUInteger startOfLine = [head length];
while (startOfLine > 0) {
    /*
     * 1. Adjust startOfLine to the beginning of the first word before startOfLine
     * 2. Check if drawing the substring of head up to startOfLine causes a reduction in height compared to initialSize.
     * 3. If so, then you've identified the start of the line containing the cursor, otherwise keep going.
     */
}
NSString* tail = [head substringFromIndex:startOfLine];
CGSize lineSize = [tail sizeWithFont:textView.font forWidth:textView.contentSize.width lineBreakMode:UILineBreakModeWordWrap];
CGPoint cursor = origin;
cursor.x += lineSize.width;
cursor.y += initialSize.height - lineSize.height;
return cursor;
}

我用 [NSCharacterSet whitespaceAndNewlineCharacterSet] 找到单词边界。

这也可以使用 CTFrameSetter 在 CoreText ，但这在iPhone OS 3.1.3中不可用，所以如果你的目标是iPhone，你需要坚持 UIStringDrawing 。

This can also be done (presumably more efficiently) using CTFrameSetter in CoreText, but that is not available in iPhone OS 3.1.3, so if you're targeting the iPhone you will need to stick to UIStringDrawing.

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