android - YouTube player API integration Error NullPointerException -

i getting error while integrating youtube player in android app. error in on line - youtubeview.initialize(config.developer_key, this);

caused by: java.lang.nullpointerexception: attempt invoke virtual method 'void com.google.android.youtube.player.youtubeplayerview.initialize(java.lang.string, com.google.android.youtube.player.youtubeplayer$oninitializedlistener)' on null object reference 

my code:

private static final int recovery_dialog_request = 1;     private youtubeplayerview youtubeview;      @override     protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_you_tube_test);         //requestwindowfeature(window.feature_no_title);         getwindow().setflags(windowmanager.layoutparams.flag_fullscreen,                 windowmanager.layoutparams.flag_fullscreen);          setcontentview(r.layout.activity_main);          youtubeview = findviewbyid(r.id.youtube_view);          // initializing video player developer key         youtubeview.initialize(config.developer_key, this);     }      @override     public void oninitializationsuccess(youtubeplayer.provider provider, youtubeplayer youtubeplayer, boolean b) {         if (!b) {              // loadvideo() auto play video             // use cuevideo() method, if don't want play automatically             youtubeplayer.loadvideo(config.youtube_video_code);              // hiding player controls             youtubeplayer.setplayerstyle(youtubeplayer.playerstyle.chromeless);         }     }      @override     public void oninitializationfailure(youtubeplayer.provider provider, youtubeinitializationresult youtubeinitializationresult) {         if (youtubeinitializationresult.isuserrecoverableerror()) {             youtubeinitializationresult.geterrordialog(this, recovery_dialog_request).show();         } else {             toast.maketext(this, youtubeinitializationresult.tostring(), toast.length_long).show();         }     }      @override     protected void onactivityresult(int requestcode, int resultcode, intent data) {         if (requestcode == recovery_dialog_request) {             // retry initialization if user performed recovery action             getyoutubeplayerprovider().initialize(config.developer_key, this);         }     }      private youtubeplayer.provider getyoutubeplayerprovider() {         return (youtubeplayerview) findviewbyid(r.id.youtube_view);     } 

get api developer key google api console , and add key in separate class below example.

public class config { private config() {} public static final string developer_key="aizasyawhk2xxxxxxx-xxxxxxxxxxxe"; }