phone volume key does not affect youtube volume (webview) - android-fragments

Question

I set a webview and load youtube.
the problem is that when I play a video in youtube, my phone volume does not affect the volume of the video playing in youtube.
I have tried with setSreanVolume as you could see in the code snippet, to no avail.
Any suggestion and help will be appreciated
public class FragmentYoutube extends Fragment {
private WebView webView;
#Nullable
#Override
public View onCreateView(#NonNull LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_youtube, container, false);
}
#Override
public void onViewCreated(#NonNull View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
webView = view.findViewById(R.id.webview_youtube);
webView.setWebChromeClient(new MyChrome());
webView.setWebViewClient(new WebViewClient());
webView.loadUrl("https://www.youtube.com");
WebSettings webSettings = webView.getSettings();
webSettings.setJavaScriptEnabled(true);
webSettings.setAllowFileAccess(true);
webView.getSettings().setCacheMode(WebSettings.LOAD_NO_CACHE);
if (savedInstanceState==null){
webView.post(new Runnable() {
#Override
public void run() {
webView.loadUrl("https://www.youtube.com");
}
});
}
AudioManager audioManager = (AudioManager) getActivity().getApplicationContext().getSystemService(Context.AUDIO_SERVICE);
audioManager.setStreamVolume(AudioManager.STREAM_MUSIC, AudioManager.FLAG_SHOW_UI, AudioManager.FLAG_PLAY_SOUND);
webView.setOnKeyListener(new View.OnKeyListener() {
#RequiresApi(api = Build.VERSION_CODES.P)
#Override
public boolean onKey(View v, int keyCode, KeyEvent event) {
if (event.getAction()== KeyEvent.ACTION_DOWN){
if (keyCode== KeyEvent.KEYCODE_BACK){
if (webView !=null){
if (webView.canGoBack()){
webView.goBack();
} else {
getActivity().onBackPressed();
}
return true;
}
}
}
return true;
}
});
}
}