Question

I’m currently working with a piece of code to detect whether a user has plugged in/unplugged headphones with their iPhone. The method I’m using to detect it is shown below.

void audioRouteChangeListenerCallback (void *inUserData, AudioSessionPropertyID inPropertyID,UInt32 inPropertyValueSize, const void *inPropertyValue){                            
    if (inPropertyID != kAudioSessionProperty_AudioRouteChange) return;

    CFStringRef route; UInt32 routeSize = sizeof(CFStringRef);
    AudioSessionGetProperty(kAudioSessionProperty_AudioRoute,&routeSize, &route);
    NSString *oldroute = (NSString*)route;
    NSLog(@"Audio Route changed to: %@",oldroute);
}

My issue occurs when I go to unplug the headphones. Plugging them in works as I expect, with the Log file showing “Audio Route changed to: Headphones”, however, when I unplug I get an empty string for oldroute. I was hoping that this value would be “Speaker” as it says in the Apple documents. Has anyone seen this before? Am I doing something wrong in getting the string oldroute? Thanks

Answer 1

I still have not found a good answer for the exact issue that I have posted as the question. Here is a workaround that may work for some people with a similar problem. This solution gives you the route that was active before the change. Ex. if you unplug your headphones you will get a string that is “Headphones” or if you put in your headphones you’ll get a string that is “Speaker”.

void audioRouteChangeListenerCallback (void *inUserData, AudioSessionPropertyID     inPropertyID,UInt32 inPropertyValueSize, const void *inPropertyValue){                            
    if (inPropertyID != kAudioSessionProperty_AudioRouteChange) return;

    CFDictionaryRef routeChangeDictionary = (CFDictionaryRef)inPropertyValue;
    CFStringRef oroute;
    oroute = (CFStringRef)CFDictionaryGetValue(routeChangeDictionary,   CFSTR(kAudioSession_AudioRouteChangeKey_OldRoute));
    NSString *oldroute = (NSString*)oroute;
}

Hope this helps.

Edit: I’m going to accept my answer until a better one comes along