_todolist.dart

/// display a dialog that accepts text
  _promptDialog(BuildContext context) {
    String _todoLabel = '';
    return showDialog(
        context: context,
        builder: (context) {
          return AlertDialog(
            title: Text('Enter TODO item'),
            content: TextField(
                onChanged: (value) => _todoLabel = value,
                decoration: InputDecoration(hintText: 'Add new TODO item')),
            actions: <Widget>[
              FlatButton(
                child: new Text('CANCEL'),
                onPressed: () => Navigator.of(context).pop(),
              ),
              FlatButton(
                child: new Text('ADD'),
                onPressed: () {
                  setState(() => todos.add(Todo(_todoLabel, false)));
                  /// dismisses the alert dialog
                  Navigator.of(context).pop();
                },
              )
            ],
          );
        });
  }