I've embedded a QLPreviewController as a sub view controller in a view controller of mine and have setup the delegate and data source for it:
qlPreviewController.delegate = self
qlPreviewController.dataSource = self
In my viewDidLoad, I'm downloading a remote document. Once it's finished downloading, I reload the QLPreviewController to display that document. This works fine.
Now, I want to show multiple documents at the same time. Therefor, I download multiple documents, setup an array of those and then reload the QLPreviewController.
Here's the implemented data source methods:
func numberOfPreviewItems(in controller: QLPreviewController) -> Int {
print("count:", downloadedDocuments.count)
return downloadedDocuments.count
}
func previewController(_ controller: QLPreviewController, previewItemAt index: Int) -> QLPreviewItem {
print("\(index+1)/\(downloadedDocuments.count), id:", downloadedDocuments[index].id)
return downloadedDocuments[index].localURL as QLPreviewItem
}
What ends up happening is that only one document is being display, which is the first in the array. I added the print statement above, to verify that there are multiple documents in the downloadedDocuments array. It prints:
count: 5
1/5, id: 251
As you can see, it's calling previewItemAtIndex only once, and the index remains 0.
Why is that? Do I need to setup anything else?
Turns out, I misunderstood how multiple items are loaded in a QLPreviewController.
I thought, the user had to scroll vertically and see the side bar with thumbnails. This is only for pages within a single document, however.
I had to scroll horizontally.
Thanks to @matt, who cleared this up for me.