AlertDialog而不是CircularProgressIndicator被消除的原因是因为AlertDialog在堆栈的顶部。这里你可以做的是在显示AlertDialog之前调用Navigator.of(Get.overlayContext).pop();来消除CircularProgressIndicator。

示例代码基于所提供的代码段。

import 'package:flutter/material.dart';
import 'package:get/get.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return GetMaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;
  final HomeController c = Get.put(HomeController());

  void _incrementCounter() {
    c.openAndCloseLoadingDialog();
    // setState(() {
    //   _counter++;
    // });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}

class HomeController extends GetxController {

  Future<void> openAndCloseLoadingDialog() async {
    showDialog(
      context: Get.overlayContext,
      barrierDismissible: false,
      builder: (_) => WillPopScope(
        onWillPop: () async => false,
        child: Center(
          child: SizedBox(
            width: 60,
            height: 60,
            child: CircularProgressIndicator(
              strokeWidth: 10,
            ),
          ),
        ),
      ),
    );

    await Future.delayed(Duration(seconds: 3));
    // Dismiss CircularProgressIndicator
    Navigator.of(Get.overlayContext).pop();

    Get.dialog(
      AlertDialog(
        title: Text("This should not be closed automatically"),
        content: Text("This should not be closed automatically"),
        actions: <Widget>[
          FlatButton(
            child: Text("CLOSE"),
            onPressed: () {
              Get.back();
            },
          )
        ],
      ),
      barrierDismissible: false,
    );

    // await Future.delayed(Duration(seconds: 3));
    // Navigator.of(Get.overlayContext).pop();
  }
}

我在bottomSheet()中使用了它，但它在Dialog中也能很好地工作，只需向Get.back(closeOverlays: true)添加一个参数：

Get.bottomSheet(
  WillPopScope(
    onWillPop: () async {
      Get.back(closeOverlays: true);
      return false;
    },
    child: const QuestionWidget(),
);

尝试按以下方式使用closeOverlays参数：

Get.back(closeOverlays: true);