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copied!<p>Edit:</p> <p>Though the code below works on both iOS 5 and 6, starting with iOS 6.0 there is an official way to do this, which is much much easier. Just look at the documentation of <code>MPVolumeView</code>, specifically <code>– setRouteButtonImage:forState:</code>.</p> <p>==== Old answer: ====</p> <p>This is pretty hard to accomplish, but I found a way for iOS 5.0+. First of all, add the following line to your ViewController:</p> <pre><code>#import <AudioToolbox/AudioToolbox.h> </code></pre> <p>In your viewDidLoad, you're already doing most of the things right, this is my code:</p> <pre><code>for (id current in self.volumeView.subviews){ if([current isKindOfClass:[UIButton class]]) { UIButton *airPlayButton = (UIButton*)current; self.airPlayButton = airPlayButton; [self setAirPlayButtonSelected:[self isAirPlayActive]]; [airPlayButton addObserver:self forKeyPath:@"alpha" options:NSKeyValueObservingOptionNew context:nil]; } } </code></pre> <p>Here's the helper <code>setAirPlayButtonSelected</code> method, it just sets the image:</p> <pre><code>- (void)setAirPlayButtonSelected:(BOOL)selected { UIImage* image; if (selected) { image = [UIImage imageNamed:@"button-airplay-selected"]; }else { image = [UIImage imageNamed:@"button-airplay"]; } [self.airPlayButton setImage:image forState:UIControlStateNormal]; [self.airPlayButton setImage:image forState:UIControlStateHighlighted]; [self.airPlayButton setImage:image forState:UIControlStateSelected]; } </code></pre> <p>For completion's sake, the <code>observeValueForKeyPath</code>:</p> <pre><code>- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context { if (object == self.airPlayButton && [[change valueForKey:NSKeyValueChangeNewKey] intValue] == 1) { [self setAirPlayButtonSelected:[self isAirPlayActive]]; } } </code></pre> <p>And now comes the interesting part. Here's the <code>isAirPlayActive</code> helper method. It uses the AudioSession framework to determine the currently playing audioSource. </p> <pre><code>- (BOOL)isAirPlayActive{ CFDictionaryRef currentRouteDescriptionDictionary = nil; UInt32 dataSize = sizeof(currentRouteDescriptionDictionary); AudioSessionGetProperty(kAudioSessionProperty_AudioRouteDescription, &dataSize, &currentRouteDescriptionDictionary); if (currentRouteDescriptionDictionary) { CFArrayRef outputs = CFDictionaryGetValue(currentRouteDescriptionDictionary, kAudioSession_AudioRouteKey_Outputs); if(CFArrayGetCount(outputs) > 0) { CFDictionaryRef currentOutput = CFArrayGetValueAtIndex(outputs, 0); CFStringRef outputType = CFDictionaryGetValue(currentOutput, kAudioSession_AudioRouteKey_Type); return (CFStringCompare(outputType, kAudioSessionOutputRoute_AirPlay, 0) == kCFCompareEqualTo); } } return NO; } </code></pre> <p>So all this code changes the AirPlay Button correctly on app launch. What about updates? We need to listen for AudioSource changes. Add the following line to your <code>viewDidLoad</code>:</p> <pre><code> AudioSessionAddPropertyListener (kAudioSessionProperty_AudioRouteChange, audioRouteChangeCallback, (__bridge void*)self); </code></pre> <p>Don't forget to unregister in <code>dealloc</code>:</p> <pre><code>- (void)dealloc { [self.airPlayButton removeObserver:self forKeyPath:@"alpha"]; AudioSessionRemovePropertyListenerWithUserData(kAudioSessionProperty_AudioRouteChange, audioRouteChangeCallback, (__bridge void*)self); } </code></pre> <p>And add this C function above your ViewController's <code>@implementation</code>:</p> <pre><code>void audioRouteChangeCallback (void *inUserData, AudioSessionPropertyID inPropertyID, UInt32 inPropertyValueSize, const void *inPropertyValue) { if (inPropertyID != kAudioSessionProperty_AudioRouteChange) { return; } CFDictionaryRef routeChangeDictionary = inPropertyValue; CFDictionaryRef currentRouteDescriptionDictionary = CFDictionaryGetValue(routeChangeDictionary, kAudioSession_AudioRouteChangeKey_CurrentRouteDescription); CFArrayRef outputs = CFDictionaryGetValue(currentRouteDescriptionDictionary, kAudioSession_AudioRouteKey_Outputs); if(CFArrayGetCount(outputs) > 0) { CFDictionaryRef currentOutput = CFArrayGetValueAtIndex(outputs, 0); CFStringRef outputType = CFDictionaryGetValue(currentOutput, kAudioSession_AudioRouteKey_Type); [(__bridge SettingsViewController*)inUserData setAirPlayButtonSelected:CFStringCompare(outputType, kAudioSessionOutputRoute_AirPlay, 0) == kCFCompareEqualTo]; } } </code></pre> <p>As you can see, all it does is determine whether or not an AirPlay output source is active and calls the <code>setAirPlayButtonSelected</code> method accordingly.</p> <p>See Apple's <a href="http://developer.apple.com/library/ios/#documentation/Audio/Conceptual/AudioSessionProgrammingGuide/Introduction/Introduction.html" rel="noreferrer">Audio Session Programming Guide</a>, specifically <a href="http://developer.apple.com/library/ios/#documentation/Audio/Conceptual/AudioSessionProgrammingGuide/HandlingRouteChanges/HandlingRouteChanges.html#//apple_ref/doc/uid/TP40007875-CH12-SW1" rel="noreferrer">this section</a> for detailed information on how the callbacks exactly work, etc.</p>

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