Embedded youtube on webview still playing on Android

Hi I have this code:

var movieUrl = "http://www.youtube.com/embed/" + trailerId + "?fs=1&autoplay=1";
webview = Ti.UI.createWebView({
  url : movieUrl,
  width: Titanium.UI.FILL,
  enableZoomControls: false,
  scalesPageToFit: true,
  scrollsToTop: false,
});
 
win.add(webview);
win.open();

and It's working properly but when I hit back button, home button or switch application the video is still playing. How can I close the webview or activity when I am not on the webview window.