iOS/Swift: QLPreviewController shows blank page in iOS11 - swift

Question

I've tried use QLPreviewController for file(.txt, .pdf, .docx, .xlsx, etc.) preview in my iOS project, but it is not working well in iOS 11: it shows blank page whatever use device or simulator. In iOS 10.3.1(simulator) it is working well, and everything is fine.
The below is the detail informations:
Environment:
Xcode version: 8.3.3, 9.0.1
Device: iPhone 7 Plus, Simulator
iOS version: 11.0.3(iPhone 7 Plus), 10.3.1(Simulator), 11.0.1(Simulator)
Swift version: 3.1/3.2
Code
import UIKit
import QuickLook
class QuickViewController: UIViewController {
var url: String!
var filePath: URL!
var msg: Message! {
didSet {
url = msg.content
// create document folder url
let documentsURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
// let tempDirectory = URL(fileURLWithPath: NSTemporaryDirectory())
filePath = documentsURL.appendingPathComponent((msg.content as NSString).lastPathComponent)
}
}
#IBOutlet weak var contentView: UIView!
// MARK: - Initialisation
override func viewDidLoad() {
super.viewDidLoad()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
loafFile()
}
func loafFile() {
if FileManager.default.fileExists(atPath: filePath.path) {
quickLookFile()
} else {
AppManager_Inst.download(url: "\(url!)", destinationUrl: filePath, completion: { [unowned self](succeed, msg) in
if succeed {
self.quickLookFile()
} else {
print(msg)
}
})
}
}
func quickLookFile() {
print(filePath.path)
/// Trying to read the file via FileManager to check if the filePath is correct or not
let data = FileManager.default.contents(atPath: filePath.path)
print(data)
if QLPreviewController.canPreview(filePath as NSURL) {
let QLController = QLPreviewController()
QLController.delegate = self
QLController.dataSource = self
QLController.view.frame = self.contentView.frame
self.view.addSubview(QLController.view)
} else {
print("file cannot to preview")
}
}
}
extension QuickViewController: QLPreviewControllerDataSource, QLPreviewControllerDelegate {
// QLPreviewControllerDataSource
func numberOfPreviewItems(in controller: QLPreviewController) -> Int {
return 1
}
func previewController(_ controller: QLPreviewController, previewItemAt index: Int) -> QLPreviewItem {
return filePath as NSURL
}
// QLPreviewControllerDelegate
func previewController(_ controller: QLPreviewController, shouldOpen url: URL, for item: QLPreviewItem) -> Bool {
return true
}
}
I'm not sure what I missing or something wrong here, please help.
p.s.: I'll trying the code with iPhone 5c(iOS 10.3.1) later, and the result should update to here once I've done it.

Answer 1

You did not add the current viewController as the parent class of the QLPreviewController()
Just add QLController.didMove(toParentViewController: self) after adding it to the self.view
I think this should solve your issue.