flutter column cross axis alignment

Column(  
        crossAxisAlignment: CrossAxisAlignment.center,
        mainAxisAlignment: MainAxisAlignment.center,
        verticalDirection: VerticalDirection.down,
        textBaseline: TextBaseline.alphabetic,
        textDirection: TextDirection.ltr,
        mainAxisSize: MainAxisSize.max,
        children: [
          Text('Column 1'),
          Text('Column 2')
        ],
      ),

var phoneNumber = new Row(
  mainAxisSize: MainAxisSize.min,
  children: <Widget>[
    Expanded(
      child: new Padding(
        padding: const EdgeInsets.all(20.0),
        child: countryCodePicker,
      ),
    ),
    Expanded(
      child: new Padding(
        padding: const EdgeInsets.all(20.0),
        child: mobileNumber,
      ),
    ),
  ],
);