[解決済み] iOS 8でSwiftを使ってアクティビティインジケータをテキストで表示するには？

質問

写真アプリにあるようなテキスト付きのアクティビティインジケータをプログラムで表示したいです（写真を編集して保存した後）。どうすればよいでしょうか。

どのように解決するのですか？

Xcode 9.0 - Swift 4.0。

import UIKit
class ViewController: UIViewController, UINavigationControllerDelegate, UIImagePickerControllerDelegate {
    @IBOutlet weak var imageView: UIImageView!
    @IBOutlet weak var filterButton: UIButton!
    @IBOutlet weak var saveButton: UIButton!
    let destinationUrl = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
        .appendingPathComponent("filteredImage.png")
    let imagePicker = UIImagePickerController()
    let messageFrame = UIView()
    var activityIndicator = UIActivityIndicatorView()
    var strLabel = UILabel()
    let effectView = UIVisualEffectView(effect: UIBlurEffect(style: .dark))
    func activityIndicator(_ title: String) {
        strLabel.removeFromSuperview()
        activityIndicator.removeFromSuperview()
        effectView.removeFromSuperview()
        strLabel = UILabel(frame: CGRect(x: 50, y: 0, width: 160, height: 46))
        strLabel.text = title
        strLabel.font = .systemFont(ofSize: 14, weight: .medium)
        strLabel.textColor = UIColor(white: 0.9, alpha: 0.7)
        effectView.frame = CGRect(x: view.frame.midX - strLabel.frame.width/2, y: view.frame.midY - strLabel.frame.height/2 , width: 160, height: 46)
        effectView.layer.cornerRadius = 15
        effectView.layer.masksToBounds = true
        activityIndicator = UIActivityIndicatorView(activityIndicatorStyle: .white)
        activityIndicator.frame = CGRect(x: 0, y: 0, width: 46, height: 46)
        activityIndicator.startAnimating()
        effectView.contentView.addSubview(activityIndicator)
        effectView.contentView.addSubview(strLabel)
        view.addSubview(effectView)
    }
    func saveImage() {
        do {
            try imageView.image?.data?.write(to: destinationUrl, options: .atomic)
            print("file saved")
        } catch {
            print(error)
        }
    }        
    func applyFilterToImage() {
        imageView.image = imageView.image?.applying(contrast: 1.5)
    }
    override func viewDidLoad() {
        super.viewDidLoad()
        guard let url = URL(string: "https://upload.wikimedia.org/wikipedia/commons/a/a8/VST_images_the_Lagoon_Nebula.jpg"), let data = try? Data(contentsOf: url), let image = UIImage(data: data) else { return }
        view.backgroundColor = UIColor(white: 0, alpha: 1)
        imageView.image = image
    }
    @IBAction func startSavingImage(_ sender: AnyObject) {
        saveButton.isEnabled = false
        filterButton.isEnabled = false
        activityIndicator("Saving Image")
        DispatchQueue.main.async {
            self.saveImage()
            DispatchQueue.main.async {
                self.effectView.removeFromSuperview()
                self.saveButton.isEnabled = true
                self.filterButton.isEnabled = true
            }
        }
    }
    @IBAction func filterAction(_ sender: AnyObject) {
        filterButton.isEnabled = false
        saveButton.isEnabled = false
        activityIndicator("Applying Filter")
        DispatchQueue.main.async {
            self.applyFilterToImage()
            DispatchQueue.main.async {
                self.effectView.removeFromSuperview()
                self.filterButton.isEnabled = true
                self.saveButton.isEnabled = true
            }
        }
    }
    @IBAction func cameraAction(_ sender: AnyObject) {
        if UIImagePickerController.isSourceTypeAvailable(.camera) {
            imagePicker.delegate = self
            imagePicker.sourceType = .camera
            present(imagePicker, animated: true)
        }
    }
    func imagePickerController(_ picker: UIImagePickerController, didFinishPickingImage image: UIImage!, editingInfo: [AnyHashable: Any]!) {
        dismiss(animated: true, completion: nil)
        imageView.image = image
    }
}

extension Data {
    var image: UIImage? { return UIImage(data: self) }
}

extension UIImage {
    var data: Data? { return UIImagePNGRepresentation(self) }
    func applying(contrast value: NSNumber) -> UIImage? {
        guard let ciImage = CIImage(image: self)?.applyingFilter("CIColorControls", withInputParameters: [kCIInputContrastKey: value]) else { return nil }
        UIGraphicsBeginImageContextWithOptions(size, false, scale)
        defer { UIGraphicsEndImageContext() }
        UIImage(ciImage: ciImage).draw(in: CGRect(origin: .zero, size: size))
        return UIGraphicsGetImageFromCurrentImageContext()
    }
}