当专注于TextField时，键盘将隐藏在TextField上方。下面我附上了带有代码的屏幕截图。请指导我解决此问题。

signup.dart

import 'package:flutter/material.dart';
import 'package:yfobs/utilities/desc.dart';

class SignUpPage extends StatefulWidget {
  static String tag = 'SignUpPage';
  @override
  _SignUpPageState createState() => _SignUpPageState();
}

class _SignUpPageState extends State<SignUpPage> {

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      resizeToAvoidBottomPadding: false,
      body: Container(
        width: double.infinity,
        decoration: BoxDecoration(
            gradient: LinearGradient(begin: Alignment.topCenter, colors: [
          Color(0xFF832685),
          Color(0xFFC81379),
        ])),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: <Widget>[
            SizedBox(
              height: 80,
            ),
            Padding(
              padding: EdgeInsets.only(top: 0, bottom: 20, left: 20, right: 20),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: <Widget>[
                  Text(
                    "SignUp",
                    style: TextStyle(color: Colors.white, fontSize: 28),
                  ),
                  SizedBox(
                    height: 10,
                  ),
                  Text(
                    "",
                    style: TextStyle(color: Colors.white, fontSize: 14),
                  ),
                ],
              ),
            ),
            SizedBox(
              height: 20,
            ),
            Expanded(
              child: Container(
                decoration: BoxDecoration(
                    color: Colors.white,
                    borderRadius: BorderRadius.only(
                        topLeft: Radius.circular(60),
                        topRight: Radius.circular(60))),
                child: Padding(
                  padding:
                      EdgeInsets.only(top: 20, bottom: 0, right: 20, left: 20),
                  child: Column(
                    children: <Widget>[
                      Container(
                        height: MediaQuery.of(context).size.height / 1.5,
                        width: MediaQuery.of(context).size.width,
                        padding: EdgeInsets.only(top: 60),
                        child: Column(
                          children: <Widget>[
                            Container(
                              width: MediaQuery.of(context).size.width / 1.2,
                              height: 45,
                              padding: EdgeInsets.only(
                                  top: 0, left: 16, right: 16, bottom: 0),
                              decoration: BoxDecoration(
                                  borderRadius:
                                      BorderRadius.all(Radius.circular(50)),
                                  color: Colors.white,
                                  boxShadow: [
                                    BoxShadow(
                                        color: Colors.black12, blurRadius: 5)
                                  ]),
                              child: TextField(
                                decoration: InputDecoration(
                                  border: InputBorder.none,
                                  icon: Icon(
                                    Icons.person,
                                    color: Colors.grey,
                                  ),
                                  hintText: 'Full Name',
                                ),
                              ),
                            ),

                            Container(
                              width: MediaQuery.of(context).size.width / 1.2,
                              height: 45,
                              padding: EdgeInsets.only(
                                  top: 0, left: 16, right: 16, bottom: 0),
                              margin: EdgeInsets.only(top: 16),
                              decoration: BoxDecoration(
                                  borderRadius:
                                      BorderRadius.all(Radius.circular(50)),
                                  color: Colors.white,
                                  boxShadow: [
                                    BoxShadow(
                                        color: Colors.black12, blurRadius: 5)
                                  ]),
                              child: TextField(
                                decoration: InputDecoration(
                                  border: InputBorder.none,
                                  icon: Icon(
                                    Icons.email,
                                    color: Colors.grey,
                                  ),
                                  hintText: 'Email',
                                ),
                              ),
                            ),

                            Container(
                              width: MediaQuery.of(context).size.width / 1.2,
                              height: 45,
                              padding: EdgeInsets.only(
                                  top: 0, left: 16, right: 16, bottom: 0),
                              margin: EdgeInsets.only(top: 16),
                              decoration: BoxDecoration(
                                  borderRadius:
                                      BorderRadius.all(Radius.circular(50)),
                                  color: Colors.white,
                                  boxShadow: [
                                    BoxShadow(
                                        color: Colors.black12, blurRadius: 5)
                                  ]),
                              child: TextField(
                                decoration: InputDecoration(
                                  border: InputBorder.none,
                                  icon: Icon(
                                    Icons.call,
                                    color: Colors.grey,
                                  ),
                                  hintText: 'Mobile Number',
                                ),
                              ),
                            ),

                            Container(
                              width: MediaQuery.of(context).size.width / 1.2,
                              height: 45,
                              padding: EdgeInsets.only(
                                  top: 0, left: 16, right: 16, bottom: 0),
                              margin: EdgeInsets.only(top: 16),
                              decoration: BoxDecoration(
                                  borderRadius:
                                      BorderRadius.all(Radius.circular(50)),
                                  color: Colors.white,
                                  boxShadow: [
                                    BoxShadow(
                                        color: Colors.black12, blurRadius: 5)
                                  ]),
                              child: TextField(
                                decoration: InputDecoration(
                                  border: InputBorder.none,
                                  icon: Icon(
                                    Icons.vpn_key,
                                    color: Colors.grey,
                                  ),
                                  hintText: 'Password',
                                ),
                                obscureText: true,
                              ),
                            ),
                            Spacer(),

                            Container(
                              padding: EdgeInsets.all(16),
                              width: double.infinity,
                              child: RaisedButton(
                                elevation: 5.0,
                                padding: EdgeInsets.all(12),
                                shape: RoundedRectangleBorder(
                                  borderRadius: BorderRadius.circular(30),
                                ),
                                color: Color(0xFFC81379),
                                child: Text(
                                  'Sign Up'.toUpperCase(),
                                  style: TextStyle(
                                      color: Colors.white,
                                      fontWeight: FontWeight.bold),
                                ),
                                onPressed: () {
                                  //Navigator.of(context).pushNamed('HomePage');
                                },
                              ),
                            ),

                            Align(
                              alignment: Alignment.center,
                              child: Column(
                                  mainAxisAlignment: MainAxisAlignment.center,
                                  children: <Widget>[
                                    new FlatButton(
                                      child: Padding(
                                        padding: const EdgeInsets.only(
                                            top: 0, right: 16, left: 16),
                                        child: new Text(
                                          Desc.alreadyUser,
                                          style: TextStyle(color: Colors.grey),
                                        ),
                                      ),
                                      onPressed: () {
                                        Navigator.of(context)
                                            .pushNamed('SignInPage');
                                      },
                                      color: Colors.white,
                                      highlightColor: Colors.transparent,
                                    ),
                                  ]),
                            )
                          ],
                        ),
                      ),
                    ],
                  ),
                ),
              ),
            ),
          ],
        ),
      ),
    );
  }
}