CoreAudio实现录音播音和扬声器听筒模式的切换

本例子使用Core Audio实现类似于微信的音频对讲功能，可以录音和播放并且实现了听筒模式和扬声器模式的切换。录音主要使用AVAudioRecorder类来实现录音功能，播放则使用AVAudioPlayer类来实现播放音频功能，扬声器和听筒模式的切换是通过设置AVAudioSession类的属性值来实现切换效果。

- (void)viewDidLoad
{
    [super viewDidLoad];
    //创建录音按钮
    UIButton* recorderB = [[[UIButton alloc]initWithFrame:CGRectMake(20, 220, 60, 40)]autorelease];
    [recorderB setTitle:@"record" forState:UIControlStateNormal];
    [recorderB setBackgroundColor:[UIColor grayColor]];
    [recorderB addTarget:self action:@selector(prerecord:) forControlEvents:UIControlEventTouchDown];
    [recorderB addTarget:self action:@selector(startrecord:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:recorderB];
    
    //创建播放按钮
    UIButton* play = [[[UIButton alloc]initWithFrame:CGRectMake(230, 220, 60, 40)]autorelease];
    [play setTitle:@"play" forState:UIControlStateNormal];
    [play setBackgroundColor:[UIColor grayColor]];
    [play addTarget:self action:@selector(play:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:play];
    
    //创建听筒模式和扬声器模式切换按钮
    change = [[[UISwitch alloc]initWithFrame:CGRectMake(120, 225, 40, 40)]autorelease];
    //默认设置为没有打开，则用听筒模式
    [change setOn:NO];
    [change addTarget:self action:@selector(change:) forControlEvents:UIControlEventValueChanged];
    [self.view addSubview:change];
    
}

//切换按钮事件
-(void)change:(UISwitch*)sender{
    NSLog(@"%@",NSStringFromSelector(_cmd));
     //录音的时候因为设置的音频会话是录音模式，所以录音完成后要把音频会话设置回听筒模式或者扬声器模式，根据切换器的值判断,kAudioSessionOverrideAudioRoute_None为听筒模式，kAudioSessionOverrideAudioRoute_Speaker为扬声器模式
    UInt32 audioRouteOverride = ![sender isOn] ?kAudioSessionOverrideAudioRoute_None:kAudioSessionOverrideAudioRoute_Speaker;
    AudioSessionSetProperty(kAudioSessionProperty_OverrideAudioRoute, sizeof(audioRouteOverride), &audioRouteOverride);
    AVAudioSession *audioSession = [AVAudioSession sharedInstance];
    [audioSession setActive:YES error:nil];
}

//录音事件
-(void)record:(id)sender{
        //获取当前应用的AudioSession,每个应用都有自己唯一的声频会话
        AVAudioSession * audioSession = [AVAudioSession sharedInstance];
        NSError* error1;
        //设置当前应用的声频会话为录音模式
        /*
        Use this category for background sounds such as rain, car engine noise, etc.
         Mixes with other music.
         
         AVF_EXPORT NSString *const AVAudioSessionCategoryAmbient;
         
         Use this category for background sounds.  Other music will stop playing.     AVF_EXPORT NSString *const AVAudioSessionCategorySoloAmbient;
         
         Use this category for music tracks.
         
         AVF_EXPORT NSString *const AVAudioSessionCategoryPlayback;
         
         Use this category when recording audio.
         
         AVF_EXPORT NSString *const AVAudioSessionCategoryRecord;
         
         Use this category when recording and playing back audio.
         
         AVF_EXPORT NSString *const AVAudioSessionCategoryPlayAndRecord;
         
         Use this category when using a hardware codec or signal processor while
         not playing or recording audio.
         
         AVF_EXPORT NSString *const AVAudioSessionCategoryAudioProcessing;
         */
        [audioSession setCategory:AVAudioSessionCategoryRecord error: &error1];
        //激活音频会话
        [audioSession setActive:YES error: &error1];
        NSLog(@"record...");
        //创建录音的文件保存位置
        NSString* filepath = [DOCUMENT_PATH stringByAppendingPathComponent:@"test.caf"];
        url = [[NSURL fileURLWithPath:filepath]retain];
        NSLog(@"path:%@",filepath);
        //设置录音的相关属性
        NSMutableDictionary *settings = [[NSMutableDictionary alloc] init];
        //设置音频格式
        [settings
         setValue:[NSNumber numberWithInteger:kAudioFormatLinearPCM] forKey:AVFormatIDKey];
        //设置采用率
        [settings
         setValue:[NSNumber numberWithFloat:44100.0f] forKey:AVSampleRateKey];
        //设置频道
        [settings
         setValue:[NSNumber numberWithInteger:2] forKey:AVNumberOfChannelsKey];
        //设置录音质量
        [settings
         setValue:[NSNumber numberWithInteger:AVAudioQualityHigh] forKey:AVEncoderAudioQualityKey];
        NSError* error;
        recorder = [[AVAudioRecorder alloc]initWithURL:url settings:settings error:&error];
        recorder.delegate = self;
        //录音准备，会为建立录音文件做好需要的准备
        BOOL isrecord = [recorder prepareToRecord];
        NSLog(@"isrecord:%d",isrecord);
        //正式开始录音
        [recorder record];
        NSLog(@"record begin...");

}
//手指离开点击录音按钮的事件
-(void)startrecord:(id)sender{

NSLog(@"%@",NSStringFromSelector(_cmd));
    NSTimeInterval now = [[NSDate date]timeIntervalSince1970];
    //获取长按录音按钮的时间
    NSTimeInterval offset = now - starttime;
    NSLog(@"offset:%f",offset);
    //如果长按的时间少于1秒，则不录音
    if (offset<=1) {
        [NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(record:) object:self];
    }else{
        //超过一秒，则完成录音，停止继续录音
        [self stoprecorder:recorder];
    }
}
//手指点击录音按钮时间
-(void)prerecord:(id)sender{
    NSLog(@"%@",NSStringFromSelector(_cmd));
    //获取点击的时间
    starttime = [[NSDate date]timeIntervalSince1970];
    NSLog(@"starttime:%f",starttime);
    //点击超过一秒后才正式录音
    [self performSelector:@selector(record:) withObject:self afterDelay:1];
}

//停止录音的事件
-(void)stoprecorder:(AVAudioRecorder*)sender{
    NSLog(@"%@",NSStringFromSelector(_cmd));
    //判断是否还在录音，如果是就停止
    if ([recorder isRecording]) {
        [recorder stop];
    }
   
}
//播放事件
-(void)play:(id)sender{
   
    NSLog(@"%@",NSStringFromSelector(_cmd));
    NSError* error;
    NSLog(@"url:%@",url);
    //通过AVAudioPlayer打开刚才录音的文件
    AVAudioPlayer* player = [[AVAudioPlayer alloc]initWithData:[NSData dataWithContentsOfURL:url] error:&error];
    //AVAudioPlayer预处理，为需要播放做好准备
    BOOL isplay = [player prepareToPlay];
    NSLog(@"isplay:%d",isplay);
  //  player.volume = 1;
    player.delegate = self;
    //正式播放
    [player play];
}
- (void)didReceiveMemoryWarning
{
    
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}
//录音完成后的回调事件
- (void)audioRecorderDidFinishRecording:(AVAudioRecorder *)recorder successfully:(BOOL)flag{
    NSLog(@"%@",NSStringFromSelector(_cmd));
    //录音完成后关闭释放资源
    if ([recorder isRecording]) {
        [recorder stop];
    }
    [recorder release];
    //录音的时候因为设置的音频会话是录音模式，所以录音完成后要把音频会话设置回听筒模式或者扬声器模式，根据切换器的值判断,kAudioSessionOverrideAudioRoute_None为听筒模式，kAudioSessionOverrideAudioRoute_Speaker为扬声器模式
    UInt32 audioRouteOverride = ![change isOn] ?kAudioSessionOverrideAudioRoute_None:kAudioSessionOverrideAudioRoute_Speaker;
    AudioSessionSetProperty(kAudioSessionProperty_OverrideAudioRoute, sizeof(audioRouteOverride), &audioRouteOverride);
    AVAudioSession *audioSession = [AVAudioSession sharedInstance];
    //类别要AVAudioSessionCategoryPlayAndRecord，才有效
    [audioSession setCategory:AVAudioSessionCategoryPlayAndRecord error:nil];
    [audioSession setActive:YES error:nil];
    
}

//录音编码出错的回调
- (void)audioRecorderEncodeErrorDidOccur:(AVAudioRecorder *)recorder error:(NSError *)error{
    NSLog(@"%@",NSStringFromSelector(_cmd));
    [recorder release];
}
//播放音频完成后的回调
- (void)audioPlayerDidFinishPlaying:(AVAudioPlayer *)player successfully:(BOOL)flag{
     NSLog(@"%@",NSStringFromSelector(_cmd));
    //成功播放完音频后释放资源
    if ([player isPlaying]) {
        [player stop];
    }
    [player release];
}

//音频播放解码出错的回调
- (void)audioPlayerDecodeErrorDidOccur:(AVAudioPlayer *)player error:(NSError *)error{
 NSLog(@"%@",NSStringFromSelector(_cmd));
    [player release];
}