AVSpeechSynthesizer代表不在iOS 11中调用

这是我的文字转语音代码. iOS 11以下的一切工作正常.但是在iOS 11中没有调用委托方法.

AVSpeechSynthesizerDelegate准确设置. (因为它在iOS 11下工作)

按下按钮

AVSpeechSynthesizer *synthesizer = [[AVSpeechSynthesizer alloc]init];
synthesizer.delegate = self;

AVSpeechUtterance *utterance = [AVSpeechUtterance speechUtteranceWithString:stringToSpeech];
[utterance setRate:AVSpeechUtteranceDefaultSpeechRate];
[utterance setPitchMultiplier:1];
[utterance setVolume:1];
utterance.voice = [AVSpeechSynthesisVoice voiceWithLanguage:@"en-US"];
[synthesizer speakUtterance:utterance];

这些是我实现的委托方法.

-(void)speechSynthesizer:(AVSpeechSynthesizer *)synthesizer didFinishSpeechUtterance:(AVSpeechUtterance *)utterance {
    NSLog(@"finished");
}

-(void)speechSynthesizer:(AVSpeechSynthesizer *)synthesizer didStartSpeechUtterance:(AVSpeechUtterance *)utterance{
    NSLog(@"Started");
}

有人面对这个问题吗？
任何帮助将不胜感激.

我在iOS 11.0.3上使用Xcode 9.0进行测试

你的合成器对象必须是一个属性,以便工作:).

要么你的AVSpeechSynthesizer实例,这是合成器,如下所示：

@property (strong, nonatomic) AVSpeechSynthesizer *synthesizer;

或者像readwrite一样.

@property (readwrite, strong, nonatomic) AVSpeechSynthesizer *synthesizer;

让我知道这个是否奏效.