iOS原生语音识别使用的正确姿势

语音识别技术这几年在移动App上的应用越来越广，各种第三方语音识别SDK也是层出不穷，例如科大讯飞、百度语音等，同时引入语音识别技术也是一个提高App逼格的好方法😁。所以今年的WWDC上，苹果开放了他的语音识别的API 视频在这。有了语音识别技术我们开发者就可以开发出像Siri这样炫酷的应用。我们最近也要上这个功能，所以调研一些这方面的东西。本文主要介绍iOS语音识别SDK的用法。

• 首先需要在plist文件中申请语音识别和麦克风使用权限：

  
  
• 引入头文件

#import <Speech/Speech.h>
#import <AVFoundation/AVFoundation.h>

• 申请权限

 - (void)viewDidAppear:(BOOL)animated{
    [super viewDidAppear:animated];
    __weak typeof(self) weakSelf = self;
    [SFSpeechRecognizer requestAuthorization:^(SFSpeechRecognizerAuthorizationStatus status) {
        dispatch_async(dispatch_get_main_queue(), ^{
            switch (status) {
                case SFSpeechRecognizerAuthorizationStatusNotDetermined:
                    weakSelf.recordButton.enabled = NO;
                    [weakSelf.recordButton setTitle:@"语音识别未授权" forState:UIControlStateDisabled];
                    break;
                case SFSpeechRecognizerAuthorizationStatusDenied:
                    weakSelf.recordButton.enabled = NO;
                    [weakSelf.recordButton setTitle:@"用户未授权使用语音识别" forState:UIControlStateDisabled];
                    break;
                case SFSpeechRecognizerAuthorizationStatusRestricted:
                    weakSelf.recordButton.enabled = NO;
                    [weakSelf.recordButton setTitle:@"语音识别在这台设备上受到限制" forState:UIControlStateDisabled];
                    
                    break;
                case SFSpeechRecognizerAuthorizationStatusAuthorized:
                    weakSelf.recordButton.enabled = YES;
                    [weakSelf.recordButton setTitle:@"开始录音" forState:UIControlStateNormal];
                    break;
                    
                default:
                    break;
            }
  
        });
    }];
}

• 核心代码
  • 识别实时音频流，如下

   - (void)startRecording{
        if (_recognitionTask) {
           [_recognitionTask cancel];
            _recognitionTask = nil;
         }
    
    AVAudioSession *audioSession = [AVAudioSession sharedInstance];
    NSError *error;
    [audioSession setCategory:AVAudioSessionCategoryRecord error:&error];
    NSParameterAssert(!error);
    [audioSession setMode:AVAudioSessionModeMeasurement error:&error];
    NSParameterAssert(!error);
    [audioSession setActive:YES withOptions:AVAudioSessionSetActiveOptionNotifyOthersOnDeactivation error:&error];
    NSParameterAssert(!error);
    
    _recognitionRequest = [[SFSpeechAudioBufferRecognitionRequest alloc] init];
    AVAudioInputNode *inputNode = self.audioEngine.inputNode;
    NSAssert(inputNode, @"录入设备没有准备好");
    NSAssert(_recognitionRequest, @"请求初始化失败");
    _recognitionRequest.shouldReportPartialResults = YES;
    __weak typeof(self) weakSelf = self;
    _recognitionTask = [self.speechRecognizer recognitionTaskWithRequest:_recognitionRequest resultHandler:^(SFSpeechRecognitionResult * _Nullable result, NSError * _Nullable error) {
        __strong typeof(weakSelf) strongSelf = weakSelf;
        BOOL isFinal = NO;
        if (result) {
            strongSelf.resultStringLable.text = result.bestTranscription.formattedString;
            isFinal = result.isFinal;
        }
        if (error || isFinal) {
            [self.audioEngine stop];
            [inputNode removeTapOnBus:0];
            strongSelf.recognitionTask = nil;
            strongSelf.recognitionRequest = nil;
            strongSelf.recordButton.enabled = YES;
            [strongSelf.recordButton setTitle:@"开始录音" forState:UIControlStateNormal];
        }
     
    }];
    
    AVAudioFormat *recordingFormat = [inputNode outputFormatForBus:0];
//在添加tap之前先移除上一个  不然有可能报"Terminating app due to uncaught exception 'com.apple.coreaudio.avfaudio',"之类的错误
    [inputNode removeTapOnBus:0];
    [inputNode installTapOnBus:0 bufferSize:1024 format:recordingFormat block:^(AVAudioPCMBuffer * _Nonnull buffer, AVAudioTime * _Nonnull when) {
        __strong typeof(weakSelf) strongSelf = weakSelf;
        if (strongSelf.recognitionRequest) {
            [strongSelf.recognitionRequest appendAudioPCMBuffer:buffer];
        }
    }];
    
    [self.audioEngine prepare];
    [self.audioEngine startAndReturnError:&error];
     NSParameterAssert(!error);
    self.resultStringLable.text = @"正在录音。。。";
}

   - (SFSpeechRecognizer *)speechRecognizer{
    if (!_speechRecognizer) {
        //要为语音识别对象设置语言，这里设置的是中文
        NSLocale *local =[[NSLocale alloc] initWithLocaleIdentifier:@"zh_CN"];
        
        _speechRecognizer =[[SFSpeechRecognizer alloc] initWithLocale:local];
        _speechRecognizer.delegate = self;
    }
    return _speechRecognizer;
}

• 识别本地音频文件，如下

   - (IBAction)recognizeLocalAudioFile:(UIButton *)sender {   
//此处设置支持的语言
 NSLocale *local =[[NSLocale alloc] initWithLocaleIdentifier:@"zh_CN"];
    SFSpeechRecognizer *localRecognizer =[[SFSpeechRecognizer alloc] initWithLocale:local];
    NSURL *url =[[NSBundle mainBundle] URLForResource:@"录音.m4a" withExtension:nil];
    if (!url) return;
    SFSpeechURLRecognitionRequest *res =[[SFSpeechURLRecognitionRequest alloc] initWithURL:url];
    __weak typeof(self) weakSelf = self;
    [localRecognizer recognitionTaskWithRequest:res resultHandler:^(SFSpeechRecognitionResult * _Nullable result, NSError * _Nullable error) {
        if (error) {
            NSLog(@"语音识别解析失败,%@",error);
        }
        else
        {
            weakSelf.resultStringLable.text = result.bestTranscription.formattedString;
        }
    }];
}

• 注意
• iOS语音识别Api只支持iOS10SDK以及以后的版本，开发工具至少要Xcode8.0。
• 本文的Demo在这里下载，要看效果的话要在真机上运行。
• 谢谢阅读此文，希望它能对你有用。

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2018-03-30 更新：修复iOS11状态栏菊花一直有的bug。。。。