Flutter Widgets Not Displaying

Question

The following Flutter layout (two rows inside a column, each row containing a text widget and a field widget) compiles and runs - but the text and text field widgets are not displaying. What you are supposed to see is the word "username" followed by a text field in one row, and the word "password" followed by a text field in the next row. What am I doing wrong, please?

import 'package:flutter/material.dart';

void main() => runApp(new MyApp());

class MyApp extends StatelessWidget {
 @override
 Widget build(BuildContext context) {
   return new MaterialApp(
     title: 'Welcome to Flutter',
     home: new Scaffold(
         appBar: new AppBar(
           title: new Text('Welcome to Flutter'),
         ),
         body: new Container(
           padding: new EdgeInsets.all(20.0),
           child: new Column(
             crossAxisAlignment: CrossAxisAlignment.start,
             children: [
               new Row(
                 mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                 children: [
                   new Text('User Name'),
                   new TextField(
                     autofocus: true,
                     decoration: new InputDecoration(
                         border: InputBorder.none,
                         hintText: 'Please enter your user name'),
                   ),
                 ],
               ),
               new Row(
                 mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                 children: [
                   new Text('User Name'),
                   new TextField(
                     decoration: new InputDecoration(
                         border: InputBorder.none,
                         hintText: 'Please enter your pasword'),
                   ),
                 ],
               ),
             ],
           ),
         )),
   );
 }
}

Answer 1

Per https://stackoverflow.com/a/45990477/1649135 if you put widgets that don't have an intrinsic width inside a row, you must nest them inside a flexible widget.

import 'package:flutter/material.dart';

void main() => runApp(new MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Welcome to Flutter',
      home: new Scaffold(
          appBar: new AppBar(
            title: new Text('Welcome to Flutter'),
          ),
          body: new Container(
            padding: new EdgeInsets.all(20.0),
            child: new Column(
              mainAxisAlignment: MainAxisAlignment.spaceEvenly,
              crossAxisAlignment: CrossAxisAlignment.center,
              children: [
                new Row(
                  mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                  children: [
                    new Flexible(
                      child: new Text('User Name:'),
                    ),
                    new Flexible(
                      child: new Container(
                        margin: const EdgeInsets.all(15.0),
                        padding: const EdgeInsets.all(3.0),
                        decoration: new BoxDecoration(
                            border: new Border.all(color: Colors.blueAccent)),
                        child: new TextField(
                          style: Theme.of(context).textTheme.body1,
                        ),
                      ),
                    ),
                  ],
                ),
                new Row(
                  mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                  children: [
                    new Flexible(
                      child: new Text('Password:'),
                    ),
                    new Flexible(
                      child: new Container(
                        margin: const EdgeInsets.all(15.0),
                        padding: const EdgeInsets.all(3.0),
                        decoration: new BoxDecoration(
                            border: new Border.all(color: Colors.blueAccent)),
                        child: new TextField(
                          style: Theme.of(context).textTheme.body1,
                        ),
                      ),
                    ),
                  ],
                ),
              ],
            ),
          )),
    );
  }
}