Delegate Method: "willSpeakRangeOfSpeechString" of AVSpeechSynthesizerDelegate gets not called

In my app I want Siri to read out a text. This works fine. But I also want to use the delegate methods of AVSpeechSynthesizerDelegate. These 2 methods are called properly, but willSpeakRangeOfSpeechString not:

speechSynthesizer(_ synthesizer: AVSpeechSynthesizer, didStart utterance: AVSpeechUtterance)
speechSynthesizer(_ synthesizer: AVSpeechSynthesizer, didFinish utterance: AVSpeechUtterance)

Thats my code to generate the AVSpeechSynthesizer. This is done in didSelectItemAt of my UICollectionViewController:

let utterance = AVSpeechUtterance(string: "testString")
utterance.rate = 0.5
utterance.volume = 1

utterance.preUtteranceDelay = 0.0
utterance.postUtteranceDelay = 0.0

self.synthesizer.speak(utterance)

The AVSpeechSynthesizer is declared at the top of the class, and the delegate is set in viewDidLoad:

override func viewDidLoad() {
   super.viewDidLoad()
    self.synthesizer.delegate = self
}

Why this delegate method is`nt called?

Edit:

Of course I have implemented AVSpeechSynthesizerDelegate and imported AVFoundation.

Solution

This error made me search for 2 days straight without finding an answer, the problem is. you need to add AVSpeechSynthesizerDelegate at the top of your viewcontroller:

Update

Based off of your comments. you need to specify the utterance language. For german-- it's de-DE

  utterance.voice = AVSpeechSynthesisVoice(language: "de-DE")

List of supported languages:

[AVSpeechSynthesisVoice 0x6080000097d0] Language: ar-SA, Name: Maged, Quality: Default [com.apple.ttsbundle.Maged-compact]
[AVSpeechSynthesisVoice 0x608000009780] Language: cs-CZ, Name: Zuzana, Quality: Default [com.apple.ttsbundle.Zuzana-compact]
[AVSpeechSynthesisVoice 0x608000009440] Language: da-DK, Name: Sara, Quality: Default [com.apple.ttsbundle.Sara-compact]
[AVSpeechSynthesisVoice 0x608000009670] Language: de-DE, Name: Anna, Quality: Default [com.apple.ttsbundle.Anna-compact]
[AVSpeechSynthesisVoice 0x6080000092e0] Language: el-GR, Name: Melina, Quality: Default [com.apple.ttsbundle.Melina-compact]
[AVSpeechSynthesisVoice 0x608000009310] Language: en-AU, Name: Karen, Quality: Default [com.apple.ttsbundle.Karen-compact]
[AVSpeechSynthesisVoice 0x6080000098d0] Language: en-GB, Name: Daniel, Quality: Default [com.apple.ttsbundle.Daniel-compact]
[AVSpeechSynthesisVoice 0x6080000094e0] Language: en-IE, Name: Moira, Quality: Default [com.apple.ttsbundle.Moira-compact]
[AVSpeechSynthesisVoice 0x6080000096b0] Language: en-US, Name: Samantha, Quality: Default [com.apple.ttsbundle.Samantha-compact]
[AVSpeechSynthesisVoice 0x608000009480] Language: en-ZA, Name: Tessa, Quality: Default [com.apple.ttsbundle.Tessa-compact]
[AVSpeechSynthesisVoice 0x6080000093d0] Language: es-ES, Name: Monica, Quality: Default [com.apple.ttsbundle.Monica-compact]
[AVSpeechSynthesisVoice 0x6080000096c0] Language: es-MX, Name: Paulina, Quality: Default [com.apple.ttsbundle.Paulina-compact]
[AVSpeechSynthesisVoice 0x608000009550] Language: fi-FI, Name: Satu, Quality: Default [com.apple.ttsbundle.Satu-compact]
[AVSpeechSynthesisVoice 0x6080000094f0] Language: fr-CA, Name: Amelie, Quality: Default [com.apple.ttsbundle.Amelie-compact]
[AVSpeechSynthesisVoice 0x608000009880] Language: fr-FR, Name: Thomas, Quality: Default [com.apple.ttsbundle.Thomas-compact]
[AVSpeechSynthesisVoice 0x608000009290] Language: he-IL, Name: Carmit, Quality: Default [com.apple.ttsbundle.Carmit-compact]
[AVSpeechSynthesisVoice 0x608000009570] Language: hi-IN, Name: Lekha, Quality: Default [com.apple.ttsbundle.Lekha-compact]
[AVSpeechSynthesisVoice 0x608000009510] Language: hu-HU, Name: Mariska, Quality: Default [com.apple.ttsbundle.Mariska-compact]
[AVSpeechSynthesisVoice 0x608000009040] Language: id-ID, Name: Damayanti, Quality: Default [com.apple.ttsbundle.Damayanti-compact]
[AVSpeechSynthesisVoice 0x6080000096a0] Language: it-IT, Name: Alice, Quality: Default [com.apple.ttsbundle.Alice-compact]
[AVSpeechSynthesisVoice 0x6080000092b0] Language: ja-JP, Name: Kyoko, Quality: Default [com.apple.ttsbundle.Kyoko-compact]
[AVSpeechSynthesisVoice 0x608000009540] Language: ko-KR, Name: Yuna, Quality: Default [com.apple.ttsbundle.Yuna-compact]
[AVSpeechSynthesisVoice 0x6080000090e0] Language: nl-BE, Name: Ellen, Quality: Default [com.apple.ttsbundle.Ellen-compact]
[AVSpeechSynthesisVoice 0x608000009380] Language: nl-NL, Name: Xander, Quality: Default [com.apple.ttsbundle.Xander-compact]
[AVSpeechSynthesisVoice 0x608000009240] Language: no-NO, Name: Nora, Quality: Default [com.apple.ttsbundle.Nora-compact]
[AVSpeechSynthesisVoice 0x6080000090f0] Language: pl-PL, Name: Zosia, Quality: Default [com.apple.ttsbundle.Zosia-compact]
[AVSpeechSynthesisVoice 0x608000009250] Language: pt-BR, Name: Luciana, Quality: Default [com.apple.ttsbundle.Luciana-compact]
[AVSpeechSynthesisVoice 0x6080000094d0] Language: pt-PT, Name: Joana, Quality: Default [com.apple.ttsbundle.Joana-compact]
[AVSpeechSynthesisVoice 0x608000009210] Language: ro-RO, Name: Ioana, Quality: Default [com.apple.ttsbundle.Ioana-compact]
[AVSpeechSynthesisVoice 0x608000009130] Language: ru-RU, Name: Milena, Quality: Default [com.apple.ttsbundle.Milena-compact]
[AVSpeechSynthesisVoice 0x608000009620] Language: sk-SK, Name: Laura, Quality: Default [com.apple.ttsbundle.Laura-compact]
[AVSpeechSynthesisVoice 0x608000009730] Language: sv-SE, Name: Alva, Quality: Default [com.apple.ttsbundle.Alva-compact]
[AVSpeechSynthesisVoice 0x608000009740] Language: th-TH, Name: Kanya, Quality: Default [com.apple.ttsbundle.Kanya-compact]
[AVSpeechSynthesisVoice 0x6080000095e0] Language: tr-TR, Name: Yelda, Quality: Default [com.apple.ttsbundle.Yelda-compact]
[AVSpeechSynthesisVoice 0x608000009010] Language: zh-CN, Name: Ting-Ting, Quality: Default [com.apple.ttsbundle.Ting-Ting-compact]
[AVSpeechSynthesisVoice 0x608000009660] Language: zh-HK, Name: Sin-Ji, Quality: Default [com.apple.ttsbundle.Sin-Ji-compact]
[AVSpeechSynthesisVoice 0x608000009860] Language: zh-TW, Name: Mei-Jia, Quality: Default [com.apple.ttsbundle.Mei-Jia-compact]

e.g:

Also, don't forget to import the following frameworks:

import AVKit
import AVFoundation // mandatory

class myViewController: UITableViewController, AVSpeechSynthesizerDelegate

Finally:

func speechSynthesizer(_ synthesizer: AVSpeechSynthesizer,
                       willSpeakRangeOfSpeechString characterRange: NSRange,
                       utterance: AVSpeechUtterance){

    // Do your UI changes with characterRange
}
func speechSynthesizer(_ synthesizer: AVSpeechSynthesizer, didFinish utterance: AVSpeechUtterance) {

    print("finished")  
}