saving contents of screen in HWC

hello,

We are developing a hybrid application.

We have a requirement to save field contents of screen.

We have put the following code in custombeforeshowscreen() of custom.js,

if(screenToShow === "Screen-Name"')

  {

  var mvc1 = getCurrentMessageValueCollection();

  saveScreen(mvc1, 'Screen name');

  }

But, contents are not getting saved as per.

Kindly help.

Regards

Ajay