如何在TextFormField中用颤动改变边框的颜色

import 'package:flutter/material.dart';

class ShakingBorderFormField extends StatefulWidget {
  @override
  _ShakingBorderFormFieldState createState() => _ShakingBorderFormFieldState();
}

class _ShakingBorderFormFieldState extends State<ShakingBorderFormField>
    with SingleTickerProviderStateMixin {
  AnimationController _animationController;
  Animation<double> _animation;

  @override
  void initState() {
    super.initState();
    _animationController = AnimationController(
      vsync: this,
      duration: Duration(milliseconds: 500),
    );
    _animation = Tween(begin: -5.0, end: 5.0).animate(
      CurvedAnimation(
        parent: _animationController,
        curve: Curves.easeInOut,
      ),
    );
  }

  @override
  void dispose() {
    _animationController.dispose();
    super.dispose();
  }

  void _startAnimation() {
    _animationController.reset();
    _animationController.forward();
  }

  @override
  Widget build(BuildContext context) {
    return TextFormField(
      decoration: InputDecoration(
        labelText: 'Enter text',
        border: OutlineInputBorder(
          borderSide: BorderSide(
            color: Colors.blue,
            width: 1.0,
          ),
        ),
      ),
      onTap: _startAnimation,
      onChanged: (value) {
        // Do something with the entered text
      },
      validator: (value) {
        // Perform validation
        return null;
      },
    );
  }
}

void main() {
  runApp(MaterialApp(
    home: Scaffold(
      appBar: AppBar(
        title: Text('Shaking Border TextFormField'),
      ),
      body: Center(
        child: Padding(
          padding: EdgeInsets.all(20.0),
          child: ShakingBorderFormField(),
        ),
      ),
    ),
  ));
}