How to remove the padding on the top part of SliverAppBar in flutter?

How to remove the padding on the top part of SliverAppBar in flutter?

I want to remove the extra padding at the top,I can't get rid of it anyway.Please help me find out how to achieve expectations.

code:

 Scaffold(
  backgroundColor: Colors.green.shade200,
  appBar: null,
  body: CustomScrollView(
    slivers: <Widget>[
      SliverToBoxAdapter(
        child: Container(
          height: 200,
          color: Colors.transparent,
          child: Center(
            child: Text("SliverToBoxAdapter"),
          ),
        ),
      ),
       SliverAppBar(
        pinned: true,
        snap: false,
        floating: false,
        backgroundColor: Colors.white,
        shape:  const RoundedRectangleBorder(
            borderRadius: BorderRadius.vertical(top: Radius.circular(20)) // <-- Radius
        ),
        leadingWidth: 100,
        title: Text("title", style: TextStyle(color: Colors.blueAccent),),
        // expandedHeight: 250.0,
        // flexibleSpace: FlexibleSpaceBar(
        //   title: Text('Demo'),
        // ),
      ),
      SliverGrid(
        gridDelegate: const SliverGridDelegateWithMaxCrossAxisExtent(
          maxCrossAxisExtent: 200.0,
          mainAxisSpacing: 10.0,
          crossAxisSpacing: 10.0,
          childAspectRatio: 4.0,
        ),
        delegate: SliverChildBuilderDelegate(
              (BuildContext context, int index) {
            return Container(
              alignment: Alignment.center,
              color: Colors.teal[100 * (index % 9)],
              child: Text('Grid Item $index'),
            );
          },
          childCount: 100,
        ),
      ),
    ],
  ),
)

Wrap your widget in MediaQuery.removePadding. Example:

return MediaQuery.removePadding(
  context: context,
  removeTop: true,
  child: child,
);