如何从另一个dart文件调用alert对话框，当用户单击 addstudents.dart 中的按钮时，我想在另一个文件中创建alert对话框，以防万一它可以重用？在我的addstudents.dart中我有这个容器，请看下面的代码，谢谢。
addstudents.dart

Container(
              padding: EdgeInsets.only(top: 10),
              width: (globals.screenWidth * 0.48),
              height: (globals.screenHeight * 0.10),
              decoration:
                  BoxDecoration(borderRadius: BorderRadius.circular(10)),
              child: RaisedButton(
                shape: new RoundedRectangleBorder(
                  borderRadius: new BorderRadius.circular(10.0),
                ),
                onPressed: () {
                  // calling another file dart
                },
                color: Colors.green,
                child: RichText(
                  text: TextSpan(
                      text: "Confirmed!",
                      style: TextStyle(
                          fontWeight: FontWeight.bold,
                          fontFamily: "Nunito",
                          color: Colors.white,
                          fontSize: globals.fontsize_19)),
                ),
              ),
            ),

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这是我的alertdialog.dart

void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter',
      home: Scaffold(
          appBar: AppBar(
            title: Text('Flutter'),
          ),
          body: MyLayout()),
    );
  }
}
class MyLayout extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.all(8.0),
      child: RaisedButton(
        child: Text('Show alert'),
        onPressed: () {
          showAlertDialog(context);
        },
      ),
    );
  }
}
showAlertDialog(BuildContext context) {
  Widget okButton = FlatButton(
    child: Text("OK"),
    onPressed: () {},
  );
  AlertDialog alert = AlertDialog(
    title: Text("My title"),
    content: Text("This is my message."),
    actions: [
      okButton,
    ],
  );
  showDialog(
    context: context,
    builder: (BuildContext context) {
      return alert;
    },
  );
}

型