flutter写一个漂亮的登录界面

以下是一个简单的Flutter登录界面示例，使用了Material Design和一些简单的动画：

import 'package:flutter/material.dart';
 
void main() => runApp(MyApp());
 
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: LoginPage(),
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
    );
  }
}
 
class LoginPage extends StatefulWidget {
  @override
  _LoginPageState createState() => _LoginPageState();
}
 
class _LoginPageState extends State<LoginPage> with TickerProviderStateMixin {
  AnimationController _controller;
  Animation<Offset> _slideAnimation;
 
  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      vsync: this,
      duration: Duration(milliseconds: 300),
    );
    _slideAnimation = Tween<Offset>(
      begin: Offset(0, 1),
      end: Offset(0, 0),
    ).animate(_controller);
    _controller.forward();
  }
 
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Stack(
        fit: StackFit.expand,
        children: <Widget>[
          Image.asset(
            'assets/background.jpg',
            fit: BoxFit.cover,
            alignment: Alignment.center,
          ),
          SingleChildScrollView(
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.center,
              children: <Widget>[
                SizedBox(height: 100.0),
                Image.asset(
                  'assets/logo.png',
                  width: 200.0,
                  height: 200.0,
                ),
                SizedBox(height: 30.0),
                AnimatedBuilder(
                  animation: _controller,
                  builder: (context, child) {
                    return SlideTransition(
                      position: _slideAnimation,
                      child: child,
                    );
                  },
                  child: Padding(
                    padding: const EdgeInsets.all(30.0),
                    child: Column(
                      children: <Widget>[
                        TextField(
                          decoration: InputDecoration(
                            hintText: 'Enter your email',
                          ),
                        ),
                        SizedBox(height: 20.0),