title: Cocos2d-x app code not allowing volume control buttons to work on iPhone or iPad
body: <p>I cannot confirm whether this has been since a newer iOS version (perhaps 11 onwards) but the hardware volume buttons do not respond whilst using an app I am updating at present.
  It uses <code>SimpleAudioEngine</code> and whilst I have looked at some other projects I have that use Cocos2d-x, I have tried to use the <code>SimpleAudioEngine</code> source from there, with zero success.</p>
  
  <p>The version of cocos2d-x is v2.1.1 </p>
  
  <p>In my <code>HelloWorldScene.cpp</code> I am calling</p>
  
  <pre><code>`void HelloWorld::StartSoundAction()
  {
      if(soundflag==0)
      {
          SimpleAudioEngine::sharedEngine()-&gt;playBackgroundMusic("background_music.mp3");
          soundflag=1;
      }
      else
      {
          SimpleAudioEngine::sharedEngine()-&gt;stopAllEffects();
          SimpleAudioEngine::sharedEngine()-&gt;playEffect("choose_your_patient3.mp3");
      }
  }`
  </code></pre>
  
  <p>The music works, but I am unable to control the volume using the hardware keys on the iPhone x or the iPad Pro.</p>