If you don't want to expand your scroll view beyond the entire screen (and it won't work with autolayout anyway) there's a better way.
You can use core graphics transforms in conjunction with the contentOffset of the scroll view to accomplish the same thing.
//
// ScrollViewSnapshotter.swift
// ScrollViewSnapshotter
//
// Created by Moshe Berman on 4/10/16.
// Copyright © 2016 Moshe Berman. All rights reserved.
//
import UIKit
class ScrollViewSnapshotter: NSObject {
func PDFWithScrollView(scrollview: UIScrollView) -> NSData {
/**
* Step 1: The first thing we need is the default origin and size of our pages.
* Since bounds always start at (0, 0) and the scroll view's bounds give us
* the correct size for the visible area, we can just use that.
*
* In the United States, a standard printed page is 8.5 inches by 11 inches,
* but when generating a PDF it's simpler to keep the page size matching the
* visible area of the scroll view. We can let our printer software (such
* as the Preview app on OS X or the Printer app on iOS) do the scaling.
*
* If we wanted to scale ourselves, we could multiply each of those
* numbers by 72, to get the number of points for each dimension.
* We would have to change how we generated the the pages below, so
* for simplicity, we're going to stick to one page per screenful of content.
*/
let pageDimensions = scrollview.bounds
/**
* Step 2: Now we need to know how many pages we will need to fit our content.
* To get this, we divide our scroll views dimensions by the size
* of each page, in either direction.
* We also need to round up, so that the pages don't get clipped.
*/
let pageSize = pageDimensions.size
let totalSize = scrollview.contentSize
let numberOfPagesThatFitHorizontally = Int(ceil(totalSize.width / pageSize.width))
let numberOfPagesThatFitVertically = Int(ceil(totalSize.height / pageSize.height))
/**
* Step 3: Set up a Core Graphics PDF context.
*
* First we create a backing store for the PDF data, then
* pass it and the page dimensions to Core Graphics.
*
* We could pass in some document information here, which mostly cover PDF metadata,
* including author name, creator name (our software) and a password to
* require when viewing the PDF file.
*
* Also note that we can use UIGraphicsBeginPDFContextToFile() instead,
* which writes the PDF to a specified path. I haven't played with it, so
* I don't know if the data is written all at once, or as each page is closed.
*/
let outputData = NSMutableData()
UIGraphicsBeginPDFContextToData(outputData, pageDimensions, nil)
/**
* Step 4: Remember some state for later.
* Then we need to clear the content insets, so that our
* core graphics layer and our content offset match up.
* We don't need to reset the content offset, because that
* happens implicitly, in the loop below.
*/
let savedContentOffset = scrollview.contentOffset
let savedContentInset = scrollview.contentInset
scrollview.contentInset = UIEdgeInsetsZero
/**
* Step 6: Now we loop through the pages and generate the data for each page.
*/
if let context = UIGraphicsGetCurrentContext()
{
for indexHorizontal in 0 ..< numberOfPagesThatFitHorizontally
{
for indexVertical in 0 ..< numberOfPagesThatFitVertically
{
/**
* Step 6a: Start a new page.
*
* This automatically closes the previous page.
* There's a similar method UIGraphicsBeginPDFPageWithInfo,
* which allows you to configure the rectangle of the page and
* other metadata.
*/
UIGraphicsBeginPDFPage()
/**
* Step 6b:The trick here is to move the visible portion of the
* scroll view *and* adjust the core graphics context
* appropriately.
*
* Consider that the viewport of the core graphics context
* is attached to the top of the scroll view's content view
* and we need to push it in the opposite direction as we scroll.
* Further, anything not inside of the visible area of the scroll
* view is clipped, so scrolling will move the core graphics viewport
* out of the rendered area, producing empty pages.
*
* To counter this, we scroll the next screenful into view, and adjust
* the core graphics context. Note that core graphics uses a coordinate
* system which has the y coordinate decreasing as we go from top to bottom.
* This is the opposite of UIKit (although it matches AppKit on OS X.)
*/
let offsetHorizontal = CGFloat(indexHorizontal) * pageSize.width
let offsetVertical = CGFloat(indexVertical) * pageSize.height
scrollview.contentOffset = CGPointMake(offsetHorizontal, offsetVertical)
CGContextTranslateCTM(context, -offsetHorizontal, -offsetVertical) // NOTE: Negative offsets
/**
* Step 6c: Now we are ready to render the page.
*
* There are faster ways to snapshot a view, but this
* is the most straightforward way to render a layer
* into a context.
*/
scrollview.layer.renderInContext(context)
}
}
}
/**
* Step 7: End the document context.
*/
UIGraphicsEndPDFContext()
/**
* Step 8: Restore the scroll view.
*/
scrollview.contentInset = savedContentInset
scrollview.contentOffset = savedContentOffset
/**
* Step 9: Return the data.
* You can write it to a file, or display it the user,
* or even pass it to iOS for sharing.
*/
return outputData
}
}
Here's a blog post I wrote explaining the process.
The process for generating a PDF is very similar to snapshotting an image, except instead of pages, you'd need to make one large canvas that matches the size of the scroll view and then grab the contents in chunks.
