DART

show shadow on focus input flutter

import 'package:flutter/material.dart';
import 'package:flutter/widgets.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(),
        body: Home(),
      ),
    );
  }
}

class Home extends StatefulWidget {
  @override
  _HomeState createState() => _HomeState();
}

class _HomeState extends State<Home> {
  static GlobalKey<FormState> _formKey = new GlobalKey<FormState>();
  FocusNode focusNode;

  @override
  void initState() {
    super.initState();
    focusNode = FocusNode();
    focusNode.addListener(() => setState(() {}));
  }

  @override
  Widget build(BuildContext context) {
    return AnimatedContainer(
      duration: Duration(seconds: 5),
      margin: const EdgeInsets.all(16),
      decoration: focusNode.hasFocus ? BoxDecoration(boxShadow: [BoxShadow(blurRadius: 6)]) : null,
      child: Form(
        key: _formKey,
        child: TextFormField(
          focusNode: focusNode,
          decoration: InputDecoration(
              fillColor: Colors.white,
              hoverColor: Colors.white,
              filled: true,
              enabledBorder: OutlineInputBorder(borderSide: BorderSide.none),
              focusedBorder: OutlineInputBorder(borderSide: BorderSide(color: Colors.grey, width: 1))),
        ),
      ),
    );
  }
}