flutter close app on back button code example

Example 1: close keyboard on button click flutter

class _HomeState extends State<Home> {
 var currentFocus;
    
 unfocus() {
    currentFocus = FocusScope.of(context);

    if (!currentFocus.hasPrimaryFocus) {
      currentFocus.unfocus();
    }
  }
  
Widget build(BuildContext context) {
    return GestureDetector(
      onTap: unfocus,
      child: Scaffold(...)
      )
     }

Example 2: cordova android close app with back button

document.addEventListener("deviceready", onDeviceReady, false);

function onDeviceReady(){
    document.addEventListener("backbutton", function(e){
       if($.mobile.activePage.is('#homepage')){
           e.preventDefault();
           navigator.app.exitApp();
       }
       else {
           navigator.app.backHistory();
       }
    }, false);
}