How can I make persistent cache in an android application with a webview (xwalkView)?

Question

I use jStorage.js to manage the local storage in a web app. I run this web app in a web view built with Crosswalk. I start app and fill local storage with set function of jStorage. When I restart the app, local storage is empty. Any suggest?

This is code for XWalkView:

 XWalkView xw = (XWalkView) findViewById(R.id.xwalkWebView);
 String path = "file://" + Environment.getExternalStorageDirectory().getAbsolutePath() + "/project/index.html";

 xw.load(path, null);
 XWalkPreferences.setValue(XWalkPreferences.REMOTE_DEBUGGING, true);

Edit 1: Ok. The problem is that when I close app, android destroy cache. So. My answer is:

How can I make persistent cache in an android application with a webview (xwalkView))?