iOS 音频播放时听筒及扬声器切换

- (IBAction)playPause:(UIButton *)sender
{
    //初始化播放器的时候如下设置
    UInt32 sessionCategory = kAudioSessionCategory_MediaPlayback;
    AudioSessionSetProperty(kAudioSessionProperty_AudioCategory,
                            sizeof(sessionCategory),
                            &sessionCategory);
    
    UInt32 audioRouteOverride = kAudioSessionOverrideAudioRoute_Speaker;
    AudioSessionSetProperty (kAudioSessionProperty_OverrideAudioRoute,
                             sizeof (audioRouteOverride),
                             &audioRouteOverride);
    
    AVAudioSession *audioSession = [AVAudioSession sharedInstance];
    //默认情况下扬声器播放
    [audioSession setCategory:AVAudioSessionCategoryPlayback error:nil];
    [audioSession setActive:YES error:nil];
    
    NSError *playerError;
    myPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL URLWithString:[VoiceRecorderBaseVC getPathByFileName:recordedFile ofType:@"aac"]] error:&playerError];
    myPlayer.meteringEnabled = YES;
    myPlayer.delegate = self;
    
    
    if (myPlayer == nil)
    {
        NSLog(@"ERror creating player: %@", [playerError description]);
    }
   
    [self handleNotification:YES];
    [myPlayer play];
}

- (void)audioPlayerDidFinishPlaying:(AVAudioPlayer *)player successfully:(BOOL)flag
{
    NSLog(@"播放结束");
    [self handleNotification:NO];
    [myPlayer release];
}

#pragma mark - 监听听筒or扬声器
- (void) handleNotification:(BOOL)state
{
    [[UIDevice currentDevice] setProximityMonitoringEnabled:state]; //建议在播放之前设置yes，播放结束设置NO，这个功能是开启红外感应
    
    if(state)//添加监听
        [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(sensorStateChange:) name:@"UIDeviceProximityStateDidChangeNotification"
                                               object:nil];
    else//移除监听
        [[NSNotificationCenter defaultCenter] removeObserver:self name:@"UIDeviceProximityStateDidChangeNotification" object:nil];
}

//处理监听触发事件
-(void)sensorStateChange:(NSNotificationCenter *)notification;
{
    //如果此时手机靠近面部放在耳朵旁，那么声音将通过听筒输出，并将屏幕变暗（省电啊）
    if ([[UIDevice currentDevice] proximityState] == YES)
    {
        NSLog(@"Device is close to user");
        [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayAndRecord error:nil];
    }
    else
    {
        NSLog(@"Device is not close to user");
        [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback error:nil];
    }
}