Как программно обнаружить наушник в iPhone?

Я вижу, что вы используете MPMediaPlayer Framework, однако работа с микрофоном осуществляется с помощью фреймворка AVAudioPlayer, который вам нужно будет добавить в проект.

На сайте Apple есть код фреймворка AVAudioPlayer, который я использую для обработки прерываний при подключении или отключении микрофонных наушников Apple.

Посмотрите Apple iPhone Dev Center Audio Session Programming Guide.

- (void) beginInterruption {
    if (playing) {
        playing = NO;
        interruptedWhilePlaying = YES;
        [self updateUserInterface];
    }
}

NSError *activationError = nil;
- (void) endInterruption {
    if (interruptedWhilePlaying) {
        [[AVAudioSession sharedInstance] setActive: YES error: &activationError];
        [player play];
        playing = YES;
        interruptedWhilePlaying = NO;
        [self updateUserInterface];
    }
}

Мой код немного отличается, и некоторые из них могут помочь вам:

    void interruptionListenerCallback (
                                   void *inUserData,
                                   UInt32   interruptionState
) {
    // This callback, being outside the implementation block, needs a reference
    //  to the AudioViewController object
    RecordingListViewController *controller = (RecordingListViewController *) inUserData;

    if (interruptionState == kAudioSessionBeginInterruption) {

        //NSLog (@"Interrupted. Stopping playback or recording.");

        if (controller.audioRecorder) {
            // if currently recording, stop
            [controller recordOrStop: (id) controller];
        } else if (controller.audioPlayer) {
            // if currently playing, pause
            [controller pausePlayback];
            controller.interruptedOnPlayback = YES;
        }

    } else if ((interruptionState == kAudioSessionEndInterruption) && controller.interruptedOnPlayback) {
        // if the interruption was removed, and the app had been playing, resume playback
        [controller resumePlayback];
        controller.interruptedOnPlayback = NO;
    }
}

void recordingListViewMicrophoneListener (
                         void                      *inUserData,
                         AudioSessionPropertyID    inPropertyID,
                         UInt32                    inPropertyValueSize,
                         const void                *isMicConnected
                         ) {

    // ensure that this callback was invoked for a change to microphone connection
    if (inPropertyID != kAudioSessionProperty_AudioInputAvailable) {
        return;
    }

    RecordingListViewController *controller = (RecordingListViewController *) inUserData;

    // kAudioSessionProperty_AudioInputAvailable is a UInt32 (see Apple Audio Session Services Reference documentation)
    // to read isMicConnected, convert the const void pointer to a UInt32 pointer
    // then dereference the memory address contained in that pointer
    UInt32 connected = * (UInt32 *) isMicConnected;

    if (connected){
        [controller setMicrophoneConnected : YES];
    }
    else{
        [controller setMicrophoneConnected: NO];    
    }

    // check to see if microphone disconnected while recording
    // cancel the recording if it was
    if(controller.isRecording && !connected){
        [controller cancelDueToMicrophoneError];
    }
}

Если вы просто хотите проверить, подключены ли наушники в любой момент времени, не слушая изменений маршрута, вы можете просто сделать следующее:

OSStatus error = AudioSessionInitialize(NULL, NULL, NULL, NULL);
if (error) 
    NSLog("Error %d while initializing session", error);

UInt32 routeSize = sizeof (CFStringRef);
CFStringRef route;

error = AudioSessionGetProperty (kAudioSessionProperty_AudioRoute,
                                 &routeSize,
                                 &route);

if (error) 
    NSLog("Error %d while retrieving audio property", error);
else if (route == NULL) {
    NSLog(@"Silent switch is currently on");
} else  if([route isEqual:@"Headset"]) {
    NSLog(@"Using headphones");
} else {
    NSLog(@"Using %@", route);
}

Ура, Рафаэлло Коласанте