Widget not going to bottom of screen in Flutter?

Question

So I'm trying to get the REGISTER button to align on the bottom center of the screen. I'm relatively new to Flutter and am wondering if there is a way to do this easily, or do I need to rewrite a lot of code? Here's what I have so far. As you can see, I put it in an Align(), but it only goes to the bottom center of the filled area. I think what I have to do is make the outside Container() the height of the entire screen, but I also don't know how to do this. If you have a way to do this, please let me know. Thanks.

import 'package:flutter/material.dart';  class LoginSignupScreen extends StatefulWidget {   @override   _LoginSignupScreenState createState() => _LoginSignupScreenState(); }  class _LoginSignupScreenState extends State<LoginSignupScreen> {   // TRUE: register page, FALSE: login page   bool _register = true;    void _changeScreen() {     setState(() {       // sets it to the opposite of the current screen       _register = !_register;     });   }    @override   Widget build(BuildContext context) {     return Container( //      height:,       child: Column( //      mainAxisAlignment: MainAxisAlignment.start,         children: <Widget>[           Padding(             padding: const EdgeInsets.all(20),             child: Row(               mainAxisAlignment: MainAxisAlignment.center,               children: <Widget>[                 ButtonBar(                   children: <Widget>[                     MaterialButton(                       onPressed: _changeScreen,                       child: Text('REGISTER'),                     ),                     MaterialButton(                       onPressed: _changeScreen,                       child: Text('LOGIN'),                     ),                   ],                 ),               ],             ),           ),           Padding(             padding: EdgeInsets.all(20),             child: Column(               children: <Widget>[                 TextField(                   decoration: InputDecoration(                       border: InputBorder.none, hintText: 'E-MAIL'),                 ),                 TextField(                   decoration: InputDecoration(                       border: InputBorder.none, hintText: 'USERNAME'),                 ),                 TextField(                   decoration: InputDecoration(                       border: InputBorder.none, hintText: 'PASSWORD'),                 )               ],             ),           ),           Align(             alignment: FractionalOffset.bottomCenter,             child: MaterialButton(               onPressed: () => {},               child: Text(_register ? 'REGISTER' : 'LOGIN'),             ),           ),         ],       ),     );   } } 

Answer 1

You will solve using Expanded widget.

        Expanded(           child: Align(             alignment: FractionalOffset.bottomCenter,             child: MaterialButton(               onPressed: () => {},               child: Text(_register ? 'REGISTER' : 'LOGIN'),             ),           ),         ),