How to position a Widget at the bottom of a SingleChildScrollView?

The issue with SingleChildScrollView is that it shrikwrap it’s children.
So to have auto size widget in between – we need to use MediaQuery to get the screen height & SizedBox to expand – SingleChildScrollView.

Here Button will be at bottom of screen.

working Code:

double height = MediaQuery.of(context).size.height;

    SingleChildScrollView(
          child: SizedBox(
              height: height,
              child: Column(
                  crossAxisAlignment: CrossAxisAlignment.stretch,
                  mainAxisSize: MainAxisSize.max,
                  children: <Widget>[
                    Column(
                      children: <Widget>[
                        Text('Dummy'),
                        Text('Dummy'),
                        Text('Dummy'),
                      ],
                    ),
                    Spacer(),
                    FlatButton(
                      onPressed: () {},
                      child: Text('Demo'),
                    )
                  ])),
        )