Take screenshot

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// Copyright 2016 Esri.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

import UIKit
import ArcGIS

class MapViewScreenshotViewController: UIViewController {
    @IBOutlet private weak var mapView: AGSMapView!
    @IBOutlet private weak var overlayParentView: UIView!
    @IBOutlet private weak var overlayImageView: UIImageView!

    var map: AGSMap!

    var tapGestureRecognizer: UITapGestureRecognizer!

    var shutterSound: SystemSoundID = 0

    override func viewDidLoad() {
        super.viewDidLoad()

        // add the source code button item to the right of navigation bar
        (self.navigationItem.rightBarButtonItem as! SourceCodeBarButtonItem).filenames = ["MapViewScreenshotViewController"]

        // instantiate map with imagegry basemap
        self.map = AGSMap(basemapStyle: .arcGISImageryStandard)

        // assign the map to the map view
        self.mapView.map = self.map

        // initialize and assign tap gesture to hide overlay parent view
        self.tapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(MapViewScreenshotViewController.hideOverlayParentView))
        self.overlayParentView.addGestureRecognizer(self.tapGestureRecognizer)

        // add border to the overlay image view
        self.overlayImageView.layer.borderColor = UIColor.white.cgColor
        self.overlayImageView.layer.borderWidth = 2
    }

    // MARK: - Actions

    // hide the screenshot overlay view
    @objc
    func hideOverlayParentView() {
        self.overlayParentView.isHidden = true
    }

    // show the screenshot overlay view
    private func showOverlayParentView() {
        self.overlayParentView.isHidden = false
    }

    // called when the user taps on the screenshot button
    @IBAction private func screenshotAction(_ sender: AnyObject) {
        // hide the screenshot view if currently visible
        self.hideOverlayParentView()

        // the method on map view we can use to get the screenshot image
        self.mapView.exportImage { [weak self] (image: UIImage?, error: Error?) in
            if let error = error {
                self?.presentAlert(error: error)
            }
            if let image = image {
                // on completion imitate flash
                self?.imitateFlashAndPreviewImage(image)
            }
        }
    }

    // imitate the white flash screen when the user taps on the screenshot button
    private func imitateFlashAndPreviewImage(_ image: UIImage) {
        let flashView = UIView(frame: self.mapView.bounds)
        flashView.backgroundColor = .white
        self.mapView.addSubview(flashView)

        // animate the white flash view on and off to show the flash effect
        UIView.animate(
            withDuration: 0.3,
            animations: {
                flashView.alpha = 0
            },
            completion: { [weak self] (_) in
                // On completion play the shutter sound
                self?.playShutterSound()
                flashView.removeFromSuperview()
                // show the screenshot on screen
                self?.overlayImageView.image = image
                self?.showOverlayParentView()
            }
        )
    }

    // to play the shutter sound once the screenshot is taken
    func playShutterSound() {
        if self.shutterSound == 0 {
            if let filepath = Bundle.main.path(forResource: "Camera Shutter", ofType: "caf") {
                let url = URL(fileURLWithPath: filepath)
                AudioServicesCreateSystemSoundID(url as CFURL, &self.shutterSound)
            }
        }

        AudioServicesPlaySystemSound(self.shutterSound)
    }

    deinit {
        AudioServicesDisposeSystemSoundID(self.shutterSound)
    }
}