warning: attempt to present whose view is not in the window hierarchy - ios

Question

I have a UITabView in UIViewController, all tab items are linked to other UIViewControllers. I have written a swift code of downloading a file through internet. when I select second tabItem, this code runs well, it downloads and previews the downloaded file, Then when I click on first tabItem and then again click on second tabItem; file downloads well but it doesn't show any preview instead xCode gives me a warning message:
What I want is download file and preview file both should work when I again click on the second tabItem. whatever the code is.
warning: attempt to present QLPreviewController on KPIViewController whose view is not in the window hierarchy
I have found many solutions on the internet but it didn't work
first solution says to use
let viewer = UIDocumentInteractionController(URL: NSURL(fileURLWithPath: path))
UIApplication.sharedApplication().keyWindow?.rootViewController?.presentViewController(viewer, animated: true, completion: nil)
but this function
UIApplication.sharedApplication().keyWindow?.rootViewController?.presentViewController(viewer, animated: true, completion: nil)
do not accept
UIDocumentInteractionController
second solution says to override the existing presentViewController function to
override func presentViewController(viewControllerToPresent: UIViewController, animated flag: Bool, completion: (() -> Void)?) {
let APP_DELEGATE = UIApplication.sharedApplication().delegate
var presentedModalVC:UIViewController = (APP_DELEGATE!.window?!.rootViewController?.presentedViewController)!
if presentedModalVC == true {
while((presentedModalVC.presentedViewController) != nil){
presentedModalVC = presentedModalVC.presentedViewController!
}
presentedModalVC.presentViewController(viewControllerToPresent, animated: flag, completion: nil)
}
else{
APP_DELEGATE?.window!!.rootViewController?.presentViewController(viewControllerToPresent, animated: flag, completion: nil)
}
}
I tried this but it also needs a UIViewController in its parameters where I have UIDocumentInteractionController
I know these function cannot accept UIDocumentInteractionController type viewController.
here is my whole swift code:
// KPIViewController.swift
// download
//
// Created by me on 15/03/2016.
// Copyright © 2016 me. All rights reserved.
//
import UIKit
class KPIViewController: UIViewController,UITabBarDelegate, NSURLSessionDownloadDelegate, UIDocumentInteractionControllerDelegate{
#IBOutlet weak var tabBar1: UITabBar!
#IBOutlet weak var login_Item: UITabBarItem!
#IBOutlet weak var QAreport_Item: UITabBarItem!
#IBOutlet weak var KpiWebView: UIWebView!
#IBOutlet weak var progressView: UIProgressView!
var downloadTask: NSURLSessionDownloadTask!
var backgroundSession: NSURLSession!
var downloadReport:Bool!
var AuditCodeOfDashboardCell:String?
var AuditCodeForPDF:String?
let isDirectory: ObjCBool = false
override func viewDidLoad() {
super.viewDidLoad()
self.progressView.hidden = true
downloadReport = false
// Do any additional setup after loading the view.
self.tabBar1.delegate = self
}
override func viewDidAppear(animated: Bool) {
self.progressView.hidden = true
downloadReport = false
let backgroundSessionConfiguration = NSURLSessionConfiguration.backgroundSessionConfigurationWithIdentifier("backgroundSession")
backgroundSession = NSURLSession(configuration: backgroundSessionConfiguration, delegate: self, delegateQueue: NSOperationQueue.mainQueue())
progressView.setProgress(0.0, animated: false)
var requestURL = NSURL!()
var request = NSURLRequest!()
// loading data from web
if AuditCodeOfDashboardCell != nil{
print(self.AuditCodeOfDashboardCell)
requestURL = NSURL(string:“my URL string&\(AuditCodeOfDashboardCell)”)
request = NSURLRequest(URL: requestURL!)
AuditCodeForPDF = AuditCodeOfDashboardCell
AuditCodeOfDashboardCell = nil
}else{
requestURL = NSURL(string:“my URL string”)
request = NSURLRequest(URL: requestURL!)
}
KpiWebView.loadRequest(request)
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
func tabBar(tabBar: UITabBar, didSelectItem item: UITabBarItem) {
print("selected tabItem: \(item.tag)")
switch (item.tag) {
case 1:
let loginVC = self.storyboard!.instantiateViewControllerWithIdentifier("loginViewController") as! LoginView
presentViewController(loginVC, animated: true, completion: nil)
break
case 2:
if AuditCodeForPDF != nil{
downloadReport = true
let url = NSURL(string: “my URL string&\(AuditCodeForPDF)”)!
urlToDownload = url
}
// if let resultController = storyboard!.instantiateViewControllerWithIdentifier(“2”) as? QAReportViewController {
// presentViewController(resultController, animated: true, completion: nil)
// }
break
default:
break
}
if downloadReport == true{
let url = NSURL(string: “my URL string&\(AuditCodeForPDF)”)!
downloadTask = backgroundSession.downloadTaskWithURL(url)
self.progressView.hidden = false
downloadTask.resume()
downloadReport = false
}
}
// - - Handling download file- - - - - - - - -
func URLSession(session: NSURLSession,
downloadTask: NSURLSessionDownloadTask,
didFinishDownloadingToURL location: NSURL){
let path = NSSearchPathForDirectoriesInDomains(NSSearchPathDirectory.DocumentDirectory, NSSearchPathDomainMask.UserDomainMask, true)
let documentDirectoryPath:String = path.first!
let fileManager = NSFileManager()
var destinationURLForFile = NSURL(fileURLWithPath: documentDirectoryPath.stringByAppendingString("/Report.pdf"))
if fileManager.fileExistsAtPath(destinationURLForFile.path!){
// showFileWithPath(destinationURLForFile.path!)
do{
try fileManager.removeItemAtPath(destinationURLForFile.path!)
destinationURLForFile = NSURL(fileURLWithPath: documentDirectoryPath.stringByAppendingString("/Report.pdf"))
}catch{
print(error)
}
}
do {
try fileManager.moveItemAtURL(location, toURL: destinationURLForFile)
// show file
dispatch_async(dispatch_get_main_queue(), { () -> Void in
self.showFileWithPath(destinationURLForFile.path!)
})
}catch{
print("An error occurred while moving file to destination url")
}
}
func showFileWithPath(path: String){
let isFileFound:Bool? = NSFileManager.defaultManager().fileExistsAtPath(path)
if isFileFound == true{
dispatch_async(dispatch_get_main_queue(), { () -> Void in
let viewer = UIDocumentInteractionController(URL: NSURL(fileURLWithPath: path))
viewer.delegate = self
viewer.presentPreviewAnimated(true)
})
}
}
func URLSession(session: NSURLSession,
downloadTask: NSURLSessionDownloadTask,
didWriteData bytesWritten: Int64,
totalBytesWritten: Int64,
totalBytesExpectedToWrite: Int64){
progressView.setProgress(Float(totalBytesWritten)/Float(totalBytesExpectedToWrite), animated: true)
}
func documentInteractionControllerViewControllerForPreview(controller: UIDocumentInteractionController) -> UIViewController{
return self
}
func documentInteractionControllerDidEndPreview(controller: UIDocumentInteractionController) {
print("document preview ends")
}
}
I cannot find any proper solution that solve my problem. I am new with swift
please anyone on help me. Thanks in advance

Answer 1

UIDocumentInteractionController is not kind of UIViewController. So you cannot present an UIDocumentInteractionController with presentViewController: method.
Checkout https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIDocumentInteractionController_class/
You can presenting a document preview or options menus with UIDocumentInteractionController.