如何以编程方式检测 iPhone 中的耳机？

Question

我目前正在开发一个项目，该项目涉及在应用程序内部播放 iPhone 音乐库中的音乐。我使用 MPMediaPickerController 允许用户选择他们的音乐并使用 iPhone 中的 iPod 音乐播放器播放它。

但是，当用户插入耳机并将其取下时，我遇到了问题。音乐会无缘无故地突然停止播放。经过一些测试，我发现当用户从设备上拔下耳机时，iPod 播放器将暂停播放。那么有没有什么方法可以以编程方式检测耳机是否已拔出，以便我可以继续播放音乐？或者有什么方法可以防止 iPod 播放器在用户拔下耳机时暂停？

Answer 1

您应该注册 AudioRoute 更改通知并实现您想要处理路由更改的方式

    // Registers the audio route change listener callback function
    AudioSessionAddPropertyListener (kAudioSessionProperty_AudioRouteChange,
                                     audioRouteChangeListenerCallback,
                                     self);

，并且在回调中，您可以获取路由更改的原因

  CFDictionaryRef   routeChangeDictionary = inPropertyValue;

  CFNumberRef routeChangeReasonRef =
  CFDictionaryGetValue (routeChangeDictionary,
            CFSTR (kAudioSession_AudioRouteChangeKey_Reason));

  SInt32 routeChangeReason;

      CFNumberGetValue (routeChangeReasonRef, kCFNumberSInt32Type, &routeChangeReason);

  if (routeChangeReason == kAudioSessionRouteChangeReason_OldDeviceUnavailable) 
  {
       // Headset is unplugged..

  }
  if (routeChangeReason == kAudioSessionRouteChangeReason_NewDeviceAvailable)
  {
       // Headset is plugged in..                   
  }

Answer 2

如果您只想检查耳机是否在任何给定时间插入，而不监听路由变化，您可以简单地执行以下操作：

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);
}

干杯，
拉斐尔·科拉桑特

Answer 3

我看到您正在使用 MPMediaPlayer 框架，但是麦克风处理是使用 AVAudioPlayer 框架完成的，您需要将其添加到您的项目中。

Apple 的网站上有来自 AVAudioPlayer 框架的代码，我用它来处理用户插入或移除 Apple 麦克风耳机造成的中断。

查看苹果的 iPhone 开发中心音频会话编程指南。

- (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];
    }
}

我的代码有点不同，其中一些可能会对您有所帮助：

    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];
    }
}

Answer 4

大家好，只需查看 AddMusic 示例应用程序即可。将解决您所有与 iPod 相关的问题

首先使用以下代码注册 iPod 播放器以获取通知

NSNotificationCenter *notificationCenter = [NSNotificationCenter defaultCenter];

    [notificationCenter
     addObserver: self
     selector:    @selector (handle_PlaybackStateChanged:)
     name:        MPMusicPlayerControllerPlaybackStateDidChangeNotification
     object:      musicPlayer];

    [musicPlayer beginGeneratingPlaybackNotifications];

并在通知中实现以下代码

- (void) handle_PlaybackStateChanged: (id) notification 
{

    MPMusicPlaybackState playbackState = [musicPlayer playbackState];

    if (playbackState == MPMusicPlaybackStatePaused) 
    {
           [self playiPodMusic];
    } 
    else if (playbackState == MPMusicPlaybackStatePlaying) 
    {

    } 
    else if (playbackState == MPMusicPlaybackStateStopped) 
    {
        [musicPlayer stop];
    }
}