Background Image resized when Soft keyboard is shown in Android iOS Ionic Cordova

After lot of bang bang finally I found solution to Make full screen CSS background image appear behind a mobile soft keyboard activated on Browser of Anroid Phone or Ionic or Cordova app background

background:url(img/bg.png); background-repeat: no-repeat; background-size: 100% auto; background-attachment: fixed;

BACKGROUND-SIZE : 100% AUTO -- does the magic