QLThumbnailGenerator doesn't generate the thumbnail

Question

I tried using QLThumbnailGenerator in Simulator/Device for iOS and iPadOS, but it does not work. I'am able to only obtain a standard empty thumbnail but not the rich icon from my files from documents directory.

Some progress with files in sandbox but nothing useful.

Do you make it work? Maybe something with the permission is wrong...but what? From my app I am able to list files, and read (open) them.

@IBAction func generateDidSelect(_ sender: Any) {  

    let docDir = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true).last  
    print("DOC: \(docDir)")  

    let absPath = URL(fileURLWithPath: docDir ?? "").appendingPathComponent("flowers.png").absoluteString  
    //[[NSBundle mainBundle]URLForResource:@"flowers" withExtension:@"png"];  
    let fileURL = URL(fileURLWithPath: absPath)  
    fileURL.startAccessingSecurityScopedResource()  

    let size = CGSize(width: 200, height: 200)  
    let scale = UIScreen.main.scale  

    let isFile = fileURL.isFile()  
    let exists = FileManager.default.fileExists(atPath: fileURL.path)  
    print("isFILE? \(isFile ? "YES" : "NO") exists? \(exists ? "YES" : "NO") \nFILE: \(fileURL)")  

    let request = QLThumbnailGenerationRequest(fileAtURL: fileURL, size: size, scale: scale, representationTypes: QLThumbnailGenerationRequestRepresentationTypeAll)  
    //request.iconMode = YES;  

    QLThumbnailGenerator.shared().generateRepresentations(for: request, updateHandler: { thumbnail, type, error i  

        DispatchQueue.main.async(execute: {  

            print(String(format: "*** TYPE: %ld ****", Int(type)))  
            let uiimage = thumbnail?.uiImage  
            let cgImage = thumbnail?.cgImage  

            if let uiimage = uiimage {  
                print("uiimage: \(uiimage)")  
            }  
            if let cgImage = cgImage {  
                print("cgImage: \(cgImage)")  
           }  

            if uiimage != nil {  
                self.thumbnailImageView.image = uiimage  
            }  

            if error != nil {  
                if let error = error {  
                    print("ERROR: \(error)")  
                }  
                //self.thumbnailImageView.image = [UIImage imageWithContentsOfFile:fileURL.path]; // test read, works  
            }  
        })  
    })  

}  

Then I tried with an image into the bundle.

Getting the file url with:

Bundle.main.url(forResource: "flowers", withExtension: "png")  

and it magically works! ...but no with fileURLWithPath method.

But, accessing the same identical file uploaded via iTunes into the Documents directory of the app i get a read error.

2019-10-01 12:41:27.167091+0200 test_thumb_obj[618:57118] DOC: /var/mobile/Containers/Data/Application/BE4A5950-5D24-4620-A1FE-B837222E8B64/Documents  
2019-10-01 12:41:27.196739+0200 test_thumb_obj[618:57118] isFILE? YES exists? YES   
FILE: file:///var/mobile/Containers/Data/Application/BE4A5950-5D24-4620-A1FE-B837222E8B64/Documents/flowers.png  
2019-10-01 12:41:27.233546+0200 test_thumb_obj[618:57118] *** TYPE: 0 ****  
2019-10-01 12:41:27.233788+0200 test_thumb_obj[618:57118] uiimage:   
2019-10-01 12:41:27.233858+0200 test_thumb_obj[618:57118] cgImage:  (DP)  
  < (kCGColorSpaceDeviceRGB)>  
  width = 493, height = 640, bpc = 8, bpp = 32, row bytes = 1984   
  kCGImageAlphaPremultipliedFirst | kCGImageByteOrder32Little  | kCGImagePixelFormatPacked   
  is mask? No, has masking color? No, has soft mask? No, has matte? No, should interpolate? Yes  
2019-10-01 12:41:27.234761+0200 test_thumb_obj[618:57118] *** TYPE: 1 ****  
2019-10-01 12:41:27.234836+0200 test_thumb_obj[618:57118] uiimage: (null)  
2019-10-01 12:41:27.234865+0200 test_thumb_obj[618:57118] cgImage: (null)  
2019-10-01 12:41:27.234943+0200 test_thumb_obj[618:57118] ERROR: Error Domain=QLThumbnailErrorDomain Code=2 "No cached thumbnail"  
2019-10-01 12:41:27.262228+0200 test_thumb_obj[618:57118] *** TYPE: 2 ****  
2019-10-01 12:41:27.262317+0200 test_thumb_obj[618:57118] uiimage: (null)  
2019-10-01 12:41:27.262349+0200 test_thumb_obj[618:57118] cgImage: (null)  
2019-10-01 12:41:27.262452+0200 test_thumb_obj[618:57118] ERROR: Error Domain=QLThumbnailErrorDomain Code=0 "Could not generate a thum  
bnail" UserInfo={NSUnderlyingError=0x281676940 {Error Domain=NSCocoaErrorDomain Code=256 "The file couldn’t be opened."}}  

The only image a get i TYPE = 0, the white empty one.

And, as before, on simulator nothing good....

Error Domain=NSPOSIXErrorDomain Code=22 "couldn't issue sandbox extension com.apple.app-sandbox.read for...  

Some test i missed to make it working?

Answer 1

Solved on iOS13.2 beta. On device ok, still read issues on simulator