How to stop a youtube video from playing

I've been messing with the YouTube API for Android. I've got it all set up and working. I'm using my Firebase database to send all relevant info to my app in the form of a list.

It all works great: the the list shows, the video plays from the list, and it goes into full screen OK. But if I want to click another video in my list after nothing happens. So I assume I have to stop and clear my YouTubePlayerView but I don't know how to do this.

This is how I get my strings from Firebase:

 Dl_Strings dlStrings = dataSnapshot.getValue(Dl_Strings.class);        Downloadscount.add(" " + String.valueOf(dlStrings.downloads));        AppNameList.add(dlStrings.name);        urlList.add(dlStrings.url);

This is where I grab the URL and add it to my YouTube player:

mlv.setOnItemClickListener(new AdapterView.OnItemClickListener() {            @Override            public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {                urlmain = urlList.get(i).toString();                tag = TAGGER.get(i).toString();                App_DownLoadCounter();                YouTubePlayerView myoutubeplayerView = (YouTubePlayerView) ((Activity)mContext).findViewById(R.id.youtube);                YouTubePlayer.OnInitializedListener mOninitial;                mOninitial = new YouTubePlayer.OnInitializedListener() {                    @Override                    public void onInitializationSuccess(YouTubePlayer.Provider provider, YouTubePlayer youTubePlayer, boolean b) {                        youTubePlayer.loadVideo(urlmain);                    }                    @Override                    public void onInitializationFailure(YouTubePlayer.Provider provider, YouTubeInitializationResult youTubeInitializationResult) {                    }                };