如何将文本对齐到底部

Question

我正在尝试构建一个非常简单的登录页面，并且我希望“注册”文本位于屏幕底部。
我正在尝试将最后一列中的文本与屏幕底部对齐，但是以某种方式无法进行调整。
当我尝试使用Expanded窗口小部件时，IDE向我抛出一个绘制错误。

   class EmailLogin extends StatefulWidget {
  @override
  _EmailLoginState createState() => _EmailLoginState();
}

class _EmailLoginState extends State<EmailLogin> {
  final Map<String, dynamic> _formData = {'email': null, 'password': null};
  final GlobalKey<FormState> _formKey = GlobalKey<FormState>();

  Widget _emailTextField() {
    return TextFormField(
      decoration: InputDecoration(
        labelText: 'Email',
      ),
      keyboardType: TextInputType.emailAddress,
  },
  onSaved: (String value) {
    _formData['email'] = value;
  },
);
 }

  Widget _passwordTextField() {
    return TextFormField(
      obscureText: true,
      validator: (String value) {
        if (value.isEmpty || value.length < 6) {
          return "please enter valid password";
        }
      },
      onSaved: (String value) {
        _formData['password'] = value;
      },
      decoration: InputDecoration(
        labelText: 'Password',
      ),
    );
  }

  Widget _passwordConfirmTextField() {
    return TextFormField(
      obscureText: true,
      validator: (String value) {
        if (value.isEmpty || value.length < 6) {
          return "please enter valid password";
       }
      },
      onSaved: (String value) {
        _formData['password'] = value;
      },
      decoration: InputDecoration(
       labelText: 'Password',
      ),
    );
  }

  void _submitForm() {
    if (!_formKey.currentState.validate()) {
      return;
    }
    _formKey.currentState.save();
    print(_formData);
    Navigator.of(context).pushNamed('/home');
    }


@override
  Widget build(BuildContext context) {
return Scaffold(
  body: Stack(
    fit: StackFit.expand,
    children: <Widget>[
      Image(
        image: AssetImage("assets2/car.jpg"),
        fit: BoxFit.cover,
        color: Colors.black87,
        colorBlendMode: BlendMode.darken,
      ),
      SingleChildScrollView(
        child: Form(
          key: _formKey,
          child: Container(
            width: double.infinity,
            child: Column(
              children: <Widget>[
                Padding(
                  padding: const EdgeInsets.only(top: 80.0),
                  child: Logo(),
                ),
                Row(
                  mainAxisAlignment: MainAxisAlignment.center,
                  children: <Widget>[
                    Padding(
                      padding: EdgeInsets.only(top: 8.0, bottom: 80.0),
                      child: Text(
                        "Airbnb",
                        style: TextStyle(fontSize: 30.0),
                      ),
                    ),
                  ],
                ),
                Padding(
                    padding: const EdgeInsets.symmetric(horizontal: 20.0),
                    child: _emailTextField()),
                SizedBox(
                  height: 15.0,
                ),
                Padding(
                    padding: const EdgeInsets.symmetric(horizontal: 20.0),
                    child: _passwordTextField()),
                Row(
                  children: <Widget>[
                    Expanded(
                      child: Padding(
                        padding: const EdgeInsets.only(
                            left: 20.0, right: 5.0, top: 10.0),
                        child: GestureDetector(
                          onTap: () {
                            _submitForm();
                          },
                          child: Container(
                            alignment: Alignment.center,
                            height: 60.0,
                            decoration: BoxDecoration(
                                color: Color(0xFF18D191),
                                borderRadius: BorderRadius.circular(10.0)),
                            child: Text(
                              'login',
                              style: TextStyle(
                                  fontSize: 20.0, color: Colors.white),
                            ),
                          ),
                        ),
                      ),
                    ),
                    Expanded(
                      child: Padding(
                        padding: const EdgeInsets.only(
                            left: 10.0, right: 20.0, top: 10.0),
                        child: Container(
                          alignment: Alignment.center,
                          height: 70.0,
                          child: Text(
                            'Forgot Password?',
                            style: TextStyle(
                                fontSize: 15.0, color: Color(0xFF18D191)),
                          ),
                        ),
                      ),
                    ),
                  ],
                ),
                Column(
                  children: <Widget>[
                    Container(
                      child: Text("switch to sign up"),
                      alignment: Alignment.bottomCenter,
                    ),