flutter when i open keyboard the app closes code example

Example 1: how to automatically close keyboard in flutter

FocusScope.of(context).requestFocus(FocusNode());

Example 2: how i can close keyboard in flutter

class YourPage extends StatefulWidget {
  createState() => _YourPageState();
}

class _YourPageState extends State<MobileHome> {

  FocusNode focusNode = new FocusNode();
  @override
  Widget build(BuildContext context) {
  return Scaffold(
  	body: Column(
      mainAxisAlignment: MainAxisAlignment.center,
      crossAxisAlignment: CrossAxisAlignment.center,
      children: [
        TextField(
          focusNode: focusNode,
        ),
        SizedBox(height: 10,),
        RaisedButton(child: Text("UP"),onPressed: (){
          FocusScope.of(context).requestFocus(focusNode);
        },),
        SizedBox(height: 10,),
        RaisedButton(child: Text("DOWN"),onPressed: (){
          focusNode.unfocus();
        },),    
      ],
    )
  );
  }
}