NSProgressIndicator未在后台线程中更新-Swift 3

我已经建立了一个渲染器来处理图像，我想展示一下进度。虽然我似乎不知道如何更新用户界面。渲染完成后，ui将更新

这是我的设置，简化了：

DispatchQueue.global(qos: .background).async(execute: {
    for i in 0..<count {
        // CIImage manipulation and definition of progress
        DispatchQueue.main.async(execute: {
            self.progress.doubleValue = progress
        })
    }
})

DispatchQueue.global（qos:.background）.异步（执行：{
对于0中的i，请显示更多代码。您是否为进度指标设置了
minValue
和
maxValue
？进度的值是否正确地落在这些最小值和最大值之间？例如，macOS中的进度指标范围为0到100（而不是0.0和1.0，如果您来自iOS世界，您可能会想到这一点）。查看是否通过添加断点或通过添加打印语句调用代码。在for循环完成后，将调用代码get并更新ui。我将添加更多代码。所有打印（进度）直到结束时才会打印。。。
@IBAction func render_now(_ sender: Any) {

    self.render_button.isEnabled = false

    self.duration = self.player_x1?.currentItem?.asset.duration.seconds

    let videoATrack: AVAssetTrack = (self.player_x1?.currentItem?.asset.tracks(withMediaType: AVMediaTypeVideo).last)!
    self.fps = CMTimeScale(videoATrack.nominalFrameRate)
    self.frame_count = Int(self.duration! * Double(self.fps!))

    let asset_generator = AVAssetImageGenerator(asset: (self.player_x1?.currentItem?.asset)!)
    var time_zero = kCMTimeZero
    var asset_image_arr: [CGImage] = []
    do {
        for i in 0..<self.frame_count! {

            let time = Double(i) / Double(self.fps!)
            let asset_image = try asset_generator.copyCGImage(at: CMTime(seconds: time, preferredTimescale: self.fps!), actualTime: &time_zero)
            asset_image_arr.append(asset_image)

        }
    } catch {print("err")}

    let image_size = CGSize(width: asset_image_arr[0].width, height: asset_image_arr[0].height)
    var ci_image_arr: [CIImage] = []
    for i in 0..<self.frame_count! {
        ci_image_arr.append(CIImage(cgImage: asset_image_arr[i], options: nil))
    }

    let x_factor = Int(NSDecimalNumber(decimal: pow(2, self.radio_index! + 1)))

    let filter_brightness = CIFilter(name: "CIToneCurve")
    let brightness = 1.0 / CGFloat(x_factor)
    filter_brightness?.setValue(CIVector(x:0.0, y: 0.0), forKey: "inputPoint0")
    filter_brightness?.setValue(CIVector(x:0.25, y: 0.25 * brightness), forKey: "inputPoint1")
    filter_brightness?.setValue(CIVector(x:0.50, y: 0.5 * brightness), forKey: "inputPoint2")
    filter_brightness?.setValue(CIVector(x:0.75, y: 0.75 * brightness), forKey: "inputPoint3")
    filter_brightness?.setValue(CIVector(x:1.0, y: 1.0 * brightness), forKey: "inputPoint4")

    let filter_add = CIFilter(name: "CIAdditionCompositing")

    var images: [NSImage] = []

    DispatchQueue.global(qos: .background).async(execute: {

        for i in 0..<self.frame_count! / x_factor {

            filter_brightness?.setValue(ci_image_arr[i * x_factor], forKey: kCIInputImageKey)
            var ci_image: CIImage = (filter_brightness?.outputImage)!

            for x in 1..<x_factor {

                filter_brightness?.setValue(ci_image_arr[i * x_factor + x], forKey: kCIInputImageKey)
                let ci_image_add: CIImage = (filter_brightness?.outputImage)!

                filter_add?.setValue(ci_image, forKey: kCIInputImageKey)
                filter_add?.setValue(ci_image_add, forKey: kCIInputBackgroundImageKey)

                ci_image = (filter_add?.outputImage)!

            }
            let rep: NSCIImageRep = NSCIImageRep(ciImage: ci_image)
            let nsImage: NSImage = NSImage(size: rep.size)
            nsImage.addRepresentation(rep)

            images.append(nsImage)

            let progress = Double(i) / Double(self.frame_count! / x_factor - 1) * 100.0
            DispatchQueue.main.async(execute: {
                print(progress)
                self.progress.doubleValue = progress
            })

        }

    })

    let desktopURL = FileManager.default.urls(for: .desktopDirectory, in: .userDomainMask).first!

    let movie_out = MovieOut()
    movie_out.writeImagesAsMovie(images, path: self.movie_out_x_urls[self.radio_index! - 1].path, size: image_size, fps: self.fps!) { () -> () in

        let player_x = AVPlayer(url: self.movie_out_x_urls[self.radio_index! - 1])
        self.player_view.player = player_x
        self.view.addSubview(self.player_view)
        self.save_button.isEnabled = true
    }

}