iOS10でUIImagePickerController.cameraOverlayViewに設定したビューのユーザインタラクションが効かないのでサブクラスを作って回避

import UIKit

class ViewController: UIViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
    
    var imagePicker: UIImagePickerController?
    
    override func awakeFromNib() {
        // 左半分を覆うオーバレイビュー
        let halfLeftRect = CGRect(x: 0, y: 0, width: self.view.bounds.width / 2.0, height: self.view.bounds.height)
        let overlayView = UIView(frame: halfLeftRect)
        overlayView.backgroundColor = UIColor.blue
        overlayView.isUserInteractionEnabled = true // デフォルトtrueだが念のため
        
        // タップジェスチャをセット
        let tapGesture = UITapGestureRecognizer(target: self, action: #selector(ViewController.tapped(_:)))
        overlayView.addGestureRecognizer(tapGesture)
        
        // カメラ使えるかチェック
        if !UIImagePickerController.isSourceTypeAvailable(.camera) {
            print("camera isn't available")
        }
        else {
            // オーバレイをセットしたイメージピッカー
            imagePicker = UIImagePickerController()
            imagePicker!.sourceType = .camera
            imagePicker!.cameraOverlayView = overlayView
            imagePicker!.showsCameraControls = false
        }
    }
    
    func tapped(_ sender: UIGestureRecognizer) {
        print("TAPPED.")
    }
    
    override func viewDidAppear(_ animated: Bool) {
        // イメージピッカー表示
        if let imagePicker = self.imagePicker {
            present(imagePicker, animated: true, completion: nil)
        }
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>NSCameraUsageDescription</key>
	<string>許可してね</string>
	<key>CFBundleDevelopmentRegion</key>
	<string>en</string>
	<key>CFBundleExecutable</key>
	<string>$(EXECUTABLE_NAME)</string>
	<key>CFBundleIdentifier</key>
	<string>$(PRODUCT_BUNDLE_IDENTIFIER)</string>
	<key>CFBundleInfoDictionaryVersion</key>
	<string>6.0</string>
	<key>CFBundleName</key>
	<string>$(PRODUCT_NAME)</string>
	<key>CFBundlePackageType</key>
	<string>APPL</string>
	<key>CFBundleShortVersionString</key>
	<string>1.0</string>
	<key>CFBundleVersion</key>
	<string>1</string>
	<key>LSRequiresIPhoneOS</key>
	<true/>
	<key>UILaunchStoryboardName</key>
	<string>LaunchScreen</string>
	<key>UIMainStoryboardFile</key>
	<string>Main</string>
	<key>UIRequiredDeviceCapabilities</key>
	<array>
		<string>armv7</string>
	</array>
	<key>UISupportedInterfaceOrientations</key>
	<array>
		<string>UIInterfaceOrientationPortrait</string>
		<string>UIInterfaceOrientationLandscapeLeft</string>
		<string>UIInterfaceOrientationLandscapeRight</string>
	</array>
</dict>
</plist>

import UIKit

class ViewController: UIViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
    
    var imagePicker: MyImagePickerController?
    
    override func awakeFromNib() {
        // 左半分を覆うオーバレイビュー
        let halfLeftRect = CGRect(x: 0, y: 0, width: self.view.bounds.width / 2.0, height: self.view.bounds.height)
        let overlayView = UIView(frame: halfLeftRect)
        overlayView.backgroundColor = UIColor.yellow
        overlayView.isUserInteractionEnabled = true // デフォルトtrueだが念のため
        
        // タップジェスチャをセット
        let tapGesture = UITapGestureRecognizer(target: self, action: #selector(ViewController.tapped(_:)))
        overlayView.addGestureRecognizer(tapGesture)
        
        // カメラ使えるかチェック
        if !UIImagePickerController.isSourceTypeAvailable(.camera) {
            print("camera isn't available")
        }
        else {
            // オーバレイをセットしたイメージピッカー
            imagePicker = MyImagePickerController()
            imagePicker!.sourceType = .camera
            imagePicker!.cameraOverlayView = overlayView
            imagePicker!.showsCameraControls = false
        }
    }
    
    func tapped(_ sender: UIGestureRecognizer) {
        print("TAPPED.")
    }
    
    override func viewDidAppear(_ animated: Bool) {
        // イメージピッカー表示
        if let imagePicker = self.imagePicker {
            present(imagePicker, animated: true, completion: nil)
        }
    }
}

import UIKit

class MyImagePickerController: UIImagePickerController {

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
    
    // オリジナルのオーバレイビュー
    private var myCameraOverlayView: UIView?
    
    // スーパークラスのプロパティを横取りしてオリジナルオーバレイビューを表示用に利用する
    override var cameraOverlayView: UIView? {
        get {
            return myCameraOverlayView
        }
        set {
            myCameraOverlayView?.removeFromSuperview()
            if let newValue = newValue {
                myCameraOverlayView = newValue
                super.view.addSubview(newValue)
            }
        }
    }
}

（「だめなパターン」と同じ）