Why isn’t the Flutter page starting at the beginning by default?

Question

The scrollable page is starting at a place below the beginning, not in the middle, not at the end, I initially thought it was because I was using a Listview inside a Container, without specifying the heightand the widthof Container, but even after placing the result remains the same, if you can help me make the page start from the beginning thank you, follow the code,

@override

Widget build(BuildContext context) {
final double screenWidth = MediaQuery.of(context).size.width;
final double screenHeight = MediaQuery.of(context).size.height;

return PlatformScaffold(
  appBar: PlatformAppBar(
    title: Text("Relatório por Unidade"),
    android: (_) => MaterialAppBarData(
      backgroundColor: Colors.blue,
      leading: FlatButton(
        onPressed: () {
          Navigator.pop(context);
        },
        child: Icon(
          Icons.arrow_back,
          color: Colors.white,
        ),
      ),
    ),
  ),
  body: Container(
    height: MediaQuery.of(context).size.height,
    width: MediaQuery.of(context).size.width,
    color: Colors.grey[200],
    child: ListView( . . .)
    )
   )
  )
 );
}

The page starts like this,



An important observation is that when trying to scroll to the page for the beginning it goes up to the beginning, but soon back to this image above,