In the login.dart, there is a typo

[hyukjin0419]

Maybe that code should be right here. It is correct in github, but not in the code that presented in this -> https://codelabs.developers.google.com/codelabs/mdc-101-flutter#3

TextField(
decoration: const InputDecoration(
filled: true,
labelText: 'Username',
),
),
// spacer

Here the height should be 12.0, not 120.0

const SizedBox**(height: 120.0),**
// [Password]
TextField(
decoration: const InputDecoration(
filled: true,
labelText: 'Password',
),
obscureText: true,
),