UIGraphicsSetPDFContextURLForRect不会在Core Graphics PDF上创建可点击区域

Question

I am trying to create a rectangular region on my PDF that will go to a URL. The PDF is created in an iOS app using Core Graphics routines.

In a search to find anyone with a similar problem, I found this Stack Overflow question:

Embed hyperlink in PDF using Core Graphics on iOS

If I use the code provided in the answer of the above question, it sort of works for me. The text shows up and is a clickable link, but if I specify a rectangle that is much larger than the text, only the text is clickable. In addition, modified the code a bit so that I could provide a label and a URL separately, and when I did this and provided an empty string, there was nothing anywhere in the rectangle that was clickable.

However, if I use the UIKit routines for creating a PDF (basically UIGraphicsBeginPDFContextToFile and descendants), then the call to UIGraphicsSetPDFContextURLForRect creates a region in the resulting PDF file that is clickable, even if I do not provide any text.

Here is the method that I am using to create the rectangle link:

+ (void)rectLink:(NSString *)urlString frame:(CGRect)frameRect cropBox:(CGRect)cropBoxRect sourceContext:(CGContextRef)context
{
    UIGraphicsPushContext(context);

#ifdef OUTPUT_TEXT_LINK_OUTLINE
    CGContextSetLineWidth(context, 5.0);
    CGContextSetStrokeColorWithColor(context, [UIColor purpleColor].CGColor);
    CGContextStrokeRect(context, frameRect);
#endif

    NSURL *url = [NSURL URLWithString:urlString];
    UIGraphicsSetPDFContextURLForRect(url, frameRect);

    UIGraphicsPopContext();
}

(The OUTPUT_TEXT_LINK_OUTLINE define is something that I am using for testing to make sure that the rectangle I am passing in is in fact where it is supposed to be.)

And here is a call I am making to the above method on the first page of my PDF generation:

[self rectLink:@"http://stackoverflow.com" frame:CGRectMake(474,22,28,28) cropBox:cropBoxRect sourceContext:context];

The variable cropBoxRect refers to the crop box for the current page, and context is the value that I am saving from the CGPDFContextCreateWithURL call at the start of the document.

Answer 1

It is better to write your own writer for writing such annotations to pdf instead of using core graphics APIs, As Apple has not taken PDFKit to cocoa-touch,
- You can follow simplest "incremental update" approach for modifying the pdf which is mentioned in PDF reference 1.7.
- You need to search the page object number in pdf then get /Annots array in it add your annotation token, append its object number to /Annots array
- Make entries for newly added/modified tokens in xref table properly.
- Add trailer token..
This is how you can add any types of annotations into pdf.