iOS 4: Remote controls for background audio

Question

I'm currently attempting to set up background audio for an app I'm developing for iOS 4. The app doesn't have a dedicated music player viewController, however, unlike other background audio apps such as Pandora, which makes the task a bit more confusing.

I've set the appropriate Info.plist settings correctly and have an AVAudioPlayer object in my app delegate which is accessible from everywhere. When the user plays a song, I replace the AVAudioPlayer with a new one initialized with the song and play it. This all works great, except now I have no idea how to go about supporting remote control events.

Based on Apple's documentation, I have this:

- (void)viewDidAppear:(BOOL)animated {     [super viewDidAppear:animated];     [[UIApplication sharedApplication] beginReceivingRemoteControlEvents];     [self becomeFirstResponder]; }  - (void)viewWillDisappear:(BOOL)animated {     [super viewWillDisappear:animated];     [[UIApplication sharedApplication] endReceivingRemoteControlEvents];     [self resignFirstResponder]; }  - (BOOL)canBecomeFirstResponder {     return YES; }  - (void)remoteControlReceivedWithEvent:(UIEvent *)event {     switch(event.subtype) {         case UIEventSubtypeRemoteControlTogglePlayPause:             if([iPhoneAppDelegate backgroundAudioPlayer].playing)                 [iPhoneAppDelegate pauseBackgroundAudioPlayer];             else                 [iPhoneAppDelegate playBackgroundAudioPlayer];             break;     } } 

The thing is, where do I put this? Apple's documentation seems to suggest this should go in some view controller somewhere, but my app has lots of view controllers and navigation controllers. Wherever I try to put this, for some reason tapping the Toggle Play/Pause button in the multitasking tray remote controls either causes the song to just pause for a moment and then unpause, or somehow causes the song to play twice.

Answer 1

The documentation examples are a bit misleading, but there is no need to subclass anything anywhere. The correct place to put remoteControlReceivedWithEvent: is in the application delegate, as it remains in the responder chain regardless of whether the app is in the foreground or not. Also the begin/end receiving remote control events should be based on whether you actually need the events, not on the visibility of some random view.

Answer 2

I found a couple of solutions to receiving global remote control events on the Apple Developer Forums after a bit of searching.

One way is to subclass UIWindow and override its remoteControlReceivedWithEvent:.

The second, perhaps nicer way is to subclass UIApplication and override sendEvent:. That way, you can intercept all the remote control events and handle them there globally, and not have any other responders handle them later in the responder chain.

- (void)sendEvent:(UIEvent *)event {      if (event.type == UIEventTypeRemoteControl) {           // Handle event      }      else           [super sendEvent:event]; }