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, howeve

Answer 1

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];
}

Answer 2

Documentation explains it very well. https://developer.apple.com/library/ios/documentation/EventHandling/Conceptual/EventHandlingiPhoneOS/Remote-ControlEvents/Remote-ControlEvents.html

Answer 3

One thing that seems to influence this behavior is any category options you set for your AVAudioSession using setCategory:withOptions:error: instead of just setCategory:error:. In particular, from trial and error, it appears that if you set AVAudioSessionCategoryOptionMixWithOthers you will not get remote control events; the now playing controls will still control the iPod app. If you set AVAudioSessionCategoryOptionDuckOthers you will get remote control events, but it seems like there may be some ambiguity regarding which app is controlled. Setting the categoryOptions to 0 or just calling setCategory:error: works best.

Answer 4

The second method didn't work for me, sendEvent was never called. However the first method worked just nicely (subclassing UIWindow).

Answer 5

I struggled with this one for a while and none of the answers above worked. The bug in my code, and I hope that it will help someone reading this, was that I had the AudioSession set to mix with others. You want to be the foreground audio player to get Remote Control events. Check to see if you have INCORRECT code like this:

    [[AVAudioSession sharedInstance] setDelegate: self];
    [[AVAudioSession sharedInstance] setCategory: AVAudioSessionCategoryPlayback error: nil];
    UInt32 doSetProperty = 0;
    AudioSessionSetProperty (
                             kAudioSessionProperty_OverrideCategoryMixWithOthers,
                             sizeof (doSetProperty),
                             &doSetProperty
                             );
    NSError *activationError = nil;
    [[AVAudioSession sharedInstance] setActive: YES error: &activationError];       

And remove the AudioSessionSetProperty, or change doSetProperty to 1.

Answer 6

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.