可以使用 MediaQuery.of(context).padding.top 来获取当前屏幕的顶部内边距大小，再根据 AppBar 的高度来计算出需要设置的内边距大小。

示例代码：

class MyPage extends StatefulWidget {
  @override
  _MyPageState createState() => _MyPageState();
}

class _MyPageState extends State {
  double appBarHeight = 80;
  EdgeInsetsGeometry contentPadding = EdgeInsets.zero;

  @override
  Widget build(BuildContext context) {
    contentPadding = EdgeInsets.only(top: MediaQuery.of(context).padding.top + appBarHeight);

    return Scaffold(
      appBar: AppBar(
        title: Text('My Page'),
        centerTitle: true,
        elevation: 0,
        backgroundColor: Colors.blueAccent,
        leading: IconButton(
          icon: Icon(Icons.arrow_back),
          onPressed: () {},
        ),
        actions: [
          IconButton(
            icon: Icon(Icons.search),
            onPressed: () {},
          ),
          IconButton(
            icon: Icon(Icons.menu),
            onPressed: () {},
          ),
        ],
      ),
      body: Container(
        padding: contentPadding,
        child: SingleChildScrollView(
          child: Column(
            children: [
              SizedBox(
                height: 100,
                child: Placeholder(),
              ),
              SizedBox(height: 20),
              SizedBox(
                height: 100,
                child: Placeholder(),
              ),
              SizedBox(height: 20),
              SizedBox(
                height: 100,
                child: Placeholder(),
              ),
              SizedBox(height: 20),
              SizedBox(
                height: 100,
                child: Placeholder(),
              ),
              SizedBox(height: 20),
              SizedBox(
                height: 100,
                child: Placeholder(),
              ),
              SizedBox(height: 20),
              SizedBox(
                height: 100,
                child: Placeholder(),
              ),
              SizedBox(height: 20),
              SizedBox(
                height: 100,
                child: Placeholder(),
              ),
            ],
          ),
        ),
      ),
    );
  }
}