经过多次尝试（都失败了）打开第二个系统弹出窗口请求always权限，我开始想，正如Paulw11所评论的，可能问题出在Geolocator所做的通用位置权限请求上，所以我决定试试permission_handler插件（只是为了iOS启动）它确实允许检查状态和请求特定的位置权限类型。它确实起作用了。现在它最终打开第二系统弹出窗口以便用户可以将许可改变为总是，在iOS上（在模拟器和我即将退休的iPhone6上）以及Android平台上。这个通用位置权限实际上可能是iOS不显示第二个系统弹出窗口的真正原因，即使使用permission_handler也是如此Permission.location.request()没有显示系统弹出窗口，而Permission.locationWhenInUse.request()显示。下面是工作代码：
位置

/// Using permission_handler for both platforms
  Future<String> getLocationPermission() async {
    print('\n\nLocationRepository.getLocationPermission() started\n\n');
    late String permission;
    permission = await Permission.locationWhenInUse.status.then((value) {
      print(
          '\n\n LocationRepository.getLocationPermission Permission.locationWhenInUse.status is ${value.name}');

      // permission = await Permission.location.status.then((value) {
      //   print(
      //       '\n\n LocationRepository.getLocationPermission Permission.location.status is ${value.name}');
      switch (value) {
        case PermissionStatus.denied:
          return 'denied';
        case PermissionStatus.permanentlyDenied:
          return 'deniedForever';
        case PermissionStatus.limited:
          return 'limited';
        case PermissionStatus.granted:
          return 'granted';
        case PermissionStatus.restricted:
          return 'restricted';
      }
    });
    return permission;
  }

  Future<String> requestLocationPermission() async {
    print('LocationRepository.requestLocationPermission started');
    late String permission;
    // general location doesn't open the popup
    // var status = await Permission.location.status;
    // print('Permission.location.status is $status');
    var status = await Permission.locationWhenInUse.status;
    print('Permission.locationWhenInUse.status is $status');

    /// NOT Granted
    if (!status.isGranted) {
      // var status = await Permission.location.request();
      // print('Permission.location.request() status is $status');
      var status = await Permission.locationWhenInUse.request();
      print('Permission.locationWhenInUse.request() status is $status');
      if (status.isGranted) {
        permission = 'granted';
      } else {
        permission = 'denied';
      }
    }

    /// Granted
    else {
      permission = 'granted';
    }
    return permission;
  }

Bg位置

/// Using permission_handler for both
  Future<String> getLocationPermissionStatus() async {
    print('\n\nTrackingRepository.getLocationPermissionStatus() started\n\n');
    late String permission;
    permission = await Permission.locationAlways.status.then((value) {
      print(
          'TrackingRepository.getLocationPermissionStatus() Permission.locationAlways.status is: ${value.name}\n\n');
      switch (value) {
        case PermissionStatus.denied:
          return 'denied';
        case PermissionStatus.permanentlyDenied:
          return 'deniedForever';
        case PermissionStatus.limited:
          return 'limited';
        case PermissionStatus.granted:
          return 'granted';
        case PermissionStatus.restricted:
          return 'restricted';
      }
    });
    return permission;
  }

  Future<String> requestLocationPermission() async {
    late String permission;
    var locationWhenInUseStatus =
        await Permission.locationWhenInUse.status.then((value) {
      print('\n\nTrackingRepository.requestLocationPermission() iOS\n'
          'Permission.locationWhenInUse.status is: ${value.name}');
      return value;
    });

    /// locationWhenInUseStatus NOT Granted
    if (!locationWhenInUseStatus.isGranted) {
      print('\n\nTrackingRepository.requestLocationPermission() iOS\n'
          'locationWhenInUseRequest NOT Granted, we now request it');

      /// Ask locationWhileInUse permission
      var locationWhenInUseRequest =
          await Permission.locationWhenInUse.request();
      print('\n\nTrackingRepository.requestLocationPermission() iOS\n'
          'Permission.locationWhenInUse.request() status is: $locationWhenInUseRequest');

      /// locationWhenInUseRequest granted
      if (locationWhenInUseRequest.isGranted) {
        /// When in use NOW Granted
        print('\n\nTrackingRepository.requestLocationPermission() ios\n'
            'When in use NOW Granted');
        permission = 'whileInUse';
        PermissionStatus status = await Permission.locationAlways.request();
        print(
            '\n\nTrackingRepository.requestLocationPermission() ios locationWhenInUse is Now Granted\n'
            'Permission.locationAlways.request() status is: $status');

        if (status.isGranted) {
          /// Always is NOW Granted
          print('\n\nTrackingRepository.requestLocationPermission() ios\n'
              'Always use NOW Granted');
          permission = 'granted';
          print(
              '\n\nTrackingRepository.requestLocationPermission() ios locationAlways is Now Granted\n'
              'Permission.locationAlways.request() status is: $status');
        } else {
          //Do another stuff
        }
      }

      /// locationWhenInUseRequest not granted
      else {
        //The user deny the permission
        permission = 'denied';
      }
      if (locationWhenInUseRequest.isPermanentlyDenied) {
        //When the user previously rejected the permission and select never ask again
        //Open the screen of settings
        print('\n\nTrackingRepository.requestLocationPermission() iOS\n'
            'Permission.locationWhenInUse.request is isPermanentlyDenied');
        permission = 'deniedForever';
        bool didOpen = await openAppSettings();
        print(
            '\n\nTrackingRepository.requestLocationPermission() ios isPermanentlyDenied\n'
            'openAppSettings() didOpen: $didOpen');

        // TODO: re-check for locationWhenInUse permission status?
      }
    }

    /// locationWhenInUseStatus is ALREADY Granted
    else {
      print('\n\nTrackingRepository.requestLocationPermission() iOS\n'
          'locationWhenInUse ALREADY Granted, we now check for locationAlways permission');
      permission = 'whenInUse';

      var locationAlwaysStatus =
          await Permission.locationAlways.status.then((value) {
        print(
            '\n\nTrackingRepository.requestLocationPermission() iOS\nlocationWhenInUse already granted\n'
            'Permission.locationAlways.status is: ${value.name}');
        return value;
      });

      /// locationAlways is NOT Already Granted
      if (!locationAlwaysStatus.isGranted) {
        print('\n\nTrackingRepository.requestLocationPermission() iOS\n'
            'locationAlways not granted, we now ask for permission');

        /// ask locationAlways permission
        var locationAlwaysStatus = await Permission.locationAlways.request();

        /// finally it opens the system popup
        print('\n\nTrackingRepository.requestLocationPermission() iOs\n'
            'Permission.locationAlways.request() status is: $locationAlwaysStatus');

        /// locationAlways is NOW Granted
        if (locationAlwaysStatus.isGranted) {
          print('\n\nTrackingRepository.requestLocationPermission() iOS\n'
              'locationAlways was Granted upon request');
          permission = 'granted';
        }

        /// locationAlways was NOT Granted
        else {
          print('\n\nTrackingRepository.requestLocationPermission() iOS\n'
              'Permission.locationAlways.request() status was NOT Granted upon request, we now open AppSettings');
          await openAppSettings().then((value) {
            print(
                '\n\nTrackingRepository.requestLocationPermission() ios locationAlways isPermanentlyDenied\n'
                'openAppSettings() didOpen: $value');
          });
          // TODO: re-check locationAlways permission status??
        }
      }

      /// locationAlways is ALREADY Granted
      else {
        permission = 'granted';
      }
    }
    return permission;
  }