Swift 2 - 后台音频 - 收到呼叫时未调用remoteControlReceivedWithEvent

Question

在我的应用程序中，我有一个在后台播放音频的音频播放器。但是，当我收到一个电话或打开另一个应用程序时，我的应用程序中的后台音频会变为静音但remoteControlReceivedWithEvent功能未被调用。

我的功能是：

override func remoteControlReceivedWithEvent(event: UIEvent?) {

        if event!.type == UIEventType.RemoteControl {

            if event!.subtype == UIEventSubtype.RemoteControlPlay {
                //print("received remote play")
                NSNotificationCenter.defaultCenter().postNotificationName("AudioPlayerIsPlaying", object: nil)

            } else if event!.subtype == UIEventSubtype.RemoteControlPause {
                //print("received remote pause")
                NSNotificationCenter.defaultCenter().postNotificationName("AudioPlayerIsNotPlaying", object: nil)

            } else if event!.subtype == UIEventSubtype.RemoteControlNextTrack{
                //print("received next")
                nextBtn.sendActionsForControlEvents(UIControlEvents.TouchUpInside)

            }else if event!.subtype == UIEventSubtype.RemoteControlPreviousTrack{
                //print("received previus")
                backBtn.sendActionsForControlEvents(UIControlEvents.TouchUpInside)

            }else if event!.subtype == UIEventSubtype.RemoteControlTogglePlayPause{
                //print("received toggle")

                playBtn.sendActionsForControlEvents(UIControlEvents.TouchUpInside)

            }
        }
    }

如何告诉我的应用已收到来电或已打开其他应用？