iOS monitoring call state in background state
<p>My app is recording all the time and it should play sound and stop recording when phone call detected. After the phone call, recording should goes on. </p>

<p>I've had these task done with CTCallCenter in foreground.</p>

<p>However, CTCallCenter doesn't work properly while my app is in background. Even if add background flag "VoIp" to my app, CTCallCenter would miss CallDisconnected. Is this a bug of iOS?</p>

<p>So I tried "AVAudioSessionInterruptionNotification". It seemed that it never miss a single InterruptionBegin and InterruptionEnd. But It doesn't work as I need to play sound after InterruptionBegin detected. Apparently, InterruptionBegin means my audio session is inactive and no sound could be made.</p>

<p>Is there any way to make CTCallCenter workable in my case?</p>