showGeneralDialog在我们的页面上创建了一个新页面，因为这个页面我们无法控制我们的页面，这是在新页面后面。
我已经按照您的需要执行代码。您可能需要根据您的要求进行修改。它将帮助你继续前进。我们将使用Stack以及Animated Positioned来满足您的用例。
Stack有两个子组件，第一个是可见列表项，第二个是AnimatedPositioned小部件。
该示例的灵感来自AnimatedPositioned Demo
这是你的代码。

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});
  final String title;
  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  bool showModel = false;

  @override
  Widget build(BuildContext context) {
    final listItems = [0,1,2,3,4,5,6,7,8,9.10,11,12,13,14,15,16,17,18];

    return Scaffold(
      appBar: !showModel ? AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title: Text(widget.title),
       ):PreferredSize(child: SizedBox(), preferredSize: Size(0,0),),,
      body: Stack(
        children: <Widget>[
          ListView(
            children: listItems.map((e) {
              return Container(
                  height: 50,
                  child: Text('Widget number $e'));
            }).toList(),
          ),
          AnimatedPositioned(
          curve: Curves.easeOutCubic,
            height: 200,
            bottom: showModel ?
            MediaQuery.of(context).size.height - 200:
            MediaQuery.of(context).size.height,
            duration: const Duration(milliseconds: 250),
            child: Container(
              height: MediaQuery.of(context).size.height - 100,
              width: MediaQuery.of(context).size.width,
              color: Colors.white,
              child: const Center(child: Text("I am modal prompt")),
            ),)
        ],
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          setState(() {
            showModel = !showModel;
          });
          },
        child: Text("Toggle"),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}