添加一项功能来停止语音识别，即在iOS音频API中，n秒钟内没有听到语音

Question

我正在使用带有Unity本机插件的IOS Speech API构建应用程序。

Swift: stop speech recognition after x seconds of silence

我已经参照上面的URL创建了它，但是出现了以下错误。

Value of type 'SpeechRecognizer' has no member 'detectionTimer'

什么是detectionTimer？

下面是源代码。

import Foundation
import UIKit
import Speech

public class SpeechRecognizer : NSObject {
    static let sharedInstance: SpeechRecognizer = SpeechRecognizer()

    private var _unitySendMessageGameObjectName: String = "SpeechRecognizer"

    var unitySendMessageGameObjectName: String {
        get {
            return _unitySendMessageGameObjectName
        }
        set {
            _unitySendMessageGameObjectName = newValue
        }
    }




    private let speechRecognizer = SFSpeechRecognizer(locale: Locale(identifier: "ja-JP"))!

    private var recognitionRequest: SFSpeechAudioBufferRecognitionRequest?

    private var recognitionTask: SFSpeechRecognitionTask?

    private let audioEngine = AVAudioEngine()


    private override init() {
        super.init()
        speechRecognizer.delegate = self
    }



    func requestRecognizerAuthorization() {
        SFSpeechRecognizer.requestAuthorization { authStatus in
            OperationQueue.main.addOperation {
                switch authStatus {
                case .authorized:
                    self.unitySendMessage("OnAuthorized")
                    break

                case .denied:
                    // User denied access to speech recognition
                    self.unitySendMessage("OnUnauthorized")

                case .restricted:
                    // Speech recognition restricted on this device
                    self.unitySendMessage("OnUnauthorized")

                case .notDetermined:
                    // Speech recognition not yet authorized
                    self.unitySendMessage("OnUnauthorized")
                }
            }
        }
    }




    func startRecord() -> Bool {
        if audioEngine.isRunning {
            return false
        }

        try! startRecording()
        return true
    }
    func stopRecord() -> Bool {
        if !audioEngine.isRunning {
            return false
        }

        audioEngine.stop()
        recognitionRequest?.endAudio()
        return true
    }


    private func startRecording() throws {
        refreshTask()

        let audioSession = AVAudioSession.sharedInstance()
        try audioSession.setCategory(AVAudioSessionCategoryRecord)
        try audioSession.setMode(AVAudioSessionModeMeasurement)
        try audioSession.setActive(true, with: .notifyOthersOnDeactivation)


        recognitionRequest = SFSpeechAudioBufferRecognitionRequest()

        guard let inputNode = audioEngine.inputNode else { fatalError("Audio engine has no input node") }
        guard let recognitionRequest = recognitionRequest else { fatalError("Unable to created a SFSpeechAudioBufferRecognitionRequest object") }

        recognitionRequest.shouldReportPartialResults = false





        recognitionTask = speechRecognizer.recognitionTask(with: recognitionRequest) { result, error in

            var isFinal = false
            if let result = result {
                self.unitySendMessage("OnRecognized", message: result.bestTranscription.formattedString)
                isFinal = result.isFinal
                print("result\(isFinal)")
            }
            if let timer = self.detectionTimer, timer.isValid {
                if isFinal {
                    // self.unitySendMessage("OnError")
                    self.detectionTimer?.invalidate()
                }
            }
            else {
                self.detectionTimer = Timer.scheduledTimer(withTimeInterval: 1.5, repeats: false, block: { (timer) in
                    self.handleSend()
                    isFinal = true
                    timer.invalidate()
                })
            }
        }


        let recordingFormat = inputNode.outputFormat(forBus: 0)
        inputNode.installTap(onBus: 0, bufferSize: 1024, format: recordingFormat) { (buffer: AVAudioPCMBuffer, when: AVAudioTime) in
            self.recognitionRequest?.append(buffer)
        }
        try startAudioEngine()
    }


    private func refreshTask() {
        if let recognitionTask = recognitionTask {
            recognitionTask.cancel()
            self.recognitionTask = nil
        }
    }


    private func startAudioEngine() throws {
        audioEngine.prepare()
        try audioEngine.start()
    }

    func unitySendMessage(_ methodName: String, message: String = "") {
        UnitySendMessage(self.unitySendMessageGameObjectName, methodName, message)
    }
}






extension SpeechRecognizer: SFSpeechRecognizerDelegate {
    public func speechRecognizer(_ speechRecognizer: SFSpeechRecognizer, 
                                 availabilityDidChange available: Bool) {
        if (available) {
            unitySendMessage("OnAvailable")
        } else {
            unitySendMessage("OnUnavailable")
        }
    }
}