you have to do some mechanism to achieve it.
i need to sesssion out when user not use the application like not touch the application.
As you know if you are not working on some page so there is no any mouse movement. so you can do something with that.
I have same requirement I have done like this refer Mouse movement for session timeout in GWT
i create one GWT client side application and paste the compiled folder in android project asset folder.i call GWT application through web view.
I didn't check this with webview. it should work!!