Flutter カメラが内カメラに切り替わらない

Question

前提・実現したいこと

Flutterでカメラアプリを作っている者です。
ボタンを押したら、カメラが内カメラや外カメラに切り替わるような機能を実装したいです。

発生している問題・エラーメッセージ

エラーメッセージはありませんが、カメラが内カメラに切り替わりません。

該当のソースコード

import 'dart:io';
import 'package:camera/camera.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'dart:async';
import 'package:flutter_file_dialog/flutter_file_dialog.dart';
import 'package:flutter/services.dart';

  String result;
    String imagePath;
    String image;
    bool _isBusy = false;
  OpenFileDialogType _dialogType = OpenFileDialogType.image;

  SourceType _sourceType = SourceType.photoLibrary;
  bool _allowEditing = false;
  File _currentFile;
  String _savedFilePath;
  bool _localOnly = false;
  int selectedCameraIndex;
  List cameras;///````
  ///////`````↓
Future initCamera(CameraDescription cameraDescription) async {
  CameraController cameraController;
    if (cameraController != null) {
      await cameraController.dispose();
    }
}
///////``````↑
class TakePictureScreen extends StatefulWidget {
  
  final CameraDescription camera;

  const TakePictureScreen({
    Key key,
    @required this.camera,
  }) : super(key: key);

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

class TakePictureScreenState extends State<TakePictureScreen> {
  CameraController _controller;
  Future<void> _initializeControllerFuture;

  @override
  void initState() {
    super.initState();
  
    _controller = CameraController(
      
      widget.camera,
   
      ResolutionPreset.medium,
    );
  availableCameras().then((value) {////````↓
      cameras = value;
      if(cameras.length > 0){
        setState(() {
          selectedCameraIndex = 0;
        });
        initCamera(cameras[selectedCameraIndex]).then((value) {

        });
      }
  });////````↑
   
    _initializeControllerFuture = _controller.initialize();
  }

  @override
  void dispose() {
    // Dispose of the controller when the widget is disposed.
    _controller.dispose();
    super.dispose();
  }

Widget _buildControlBar() {
    return Row(
      mainAxisAlignment: MainAxisAlignment.spaceAround,
      children: <Widget>[
        IconButton(
          color: Colors.white,
          icon: Icon(Icons.flash_auto),
          onPressed: () {},
        ),
        FloatingActionButton (
        child: Icon(Icons.camera_alt),
        // Provide an onPressed callback.
        onPressed: () async {
          // Take the Picture in a try / catch block. If anything goes wrong,
          // catch the error.
          try {
            // Ensure that the camera is initialized.
            await _initializeControllerFuture;

            // Attempt to take a picture and get the file `image`
            // where it was saved.
            final image = await _controller.takePicture();
            
            // If the picture was taken, display it on a new screen.
            Navigator.push(
              context,
              MaterialPageRoute(
                builder: (context) => DisplayPictureScreen(
                
                  imagePath: image?.path,
                
                ),
              ),
            );
          } catch (e) {
            // If an error occurs, log the error to the console.
            print(e);
          }
        },
      ),
        IconButton(
          color: Colors.white,
          icon: Icon(Icons.switch_camera),
          onPressed:(){onSwitchCamera();}
        ),
      ],
    );
  }
  

  onSwitchCamera() {/////```````↓
    selectedCameraIndex =
        selectedCameraIndex < cameras.length - 1 ? selectedCameraIndex + 1 : 0;
    CameraDescription selectedCamera = cameras[selectedCameraIndex];
    initCamera(selectedCamera);
  }///////```````↑
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Take a picture')),
      // Wait until the controller is initialized before displaying the
      // camera preview. Use a FutureBuilder to display a loading spinner
      // until the controller has finished initializing.
body: Stack(
        children: <Widget>[
          FutureBuilder<void>(
            future: _initializeControllerFuture,
              builder: (context, snapshot) {
                if (snapshot.connectionState == ConnectionState.done) {
                  return CameraPreview(_controller);
                } else {
                  return Center(child: CircularProgressIndicator());
                }
            },
          ),
          Column(
            mainAxisAlignment: MainAxisAlignment.end,
            children: <Widget>[
          
          _buildControlBar(),
          Container(
                padding: EdgeInsets.symmetric(vertical: 10.0),
                child: Text(
                    'Tap for photo',
                    style: Theme.of(context)
                        .textTheme
                        .subtitle1
                        .copyWith(color: Colors.white),
                ),
          )
        ],
      ),
        ],
),
  
    );
  }

  
}

// A widget that displays the picture taken by the user.
class DisplayPictureScreen extends StatefulWidget {
  final String imagePath;
  DisplayPictureScreen({Key key, this.imagePath}) ;

  @override
  _DisplayPictureScreenState createState() => _DisplayPictureScreenState(imagePath:imagePath);
  
}

class _DisplayPictureScreenState extends State<DisplayPictureScreen>{
  final String imagePath;
  _DisplayPictureScreenState({this.imagePath});
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Display the Picture')),
      // The image is stored as a file on the device. Use the `Image.file`
      // constructor with the given path to display the image.
      body: Image.file(File(imagePath)),
  
          
          floatingActionButton:FloatingActionButton(
          onPressed:imagePath==null?null :()=> _saveFile(false),
          child:Text('save'),
                
        
          ),
      
    );
  }
  Future<void> _saveFile(bool useData) async {

    try {
      setState(() {
        _isBusy = true;
        if(imagePath!=null){
        _currentFile = File(imagePath);
        }else{
          _currentFile=null;
        }
      
      });
      final data = useData ? await _currentFile.readAsBytes() : null;
      final params = SaveFileDialogParams(
          sourceFilePath: useData ? null : _currentFile.path,
          data: data,
          localOnly: _localOnly,
          fileName: useData ? "untitled" : null);
      result= await FlutterFileDialog.saveFile(params: params);
      print(result);
    } on PlatformException catch (e) {
      print(e);
    } finally {
      setState(() {
        _savedFilePath = result ?? _savedFilePath;
        _isBusy = false;
      });
    }
  }
}

試したこと

このコードを参考に内カメラに切り替わる機能を追加しようとしたのですが、うまくいきませんでした。

補足情報（FW/ツールのバージョンなど）

pubspec.yamlのdependenciesは以下の通りです。
camera: ^0.7.0+2
flutter_file_dialog: ^1.0.0
よろしくお願いいたします。