Идемпотентные сценарии PostgreSQL DDL

Я решил свою проблему.

Я сделал отдельный файл selfie_camara_widget.dart

import 'dart:async';
import 'dart:io';

import 'package:camera/camera.dart';
import 'package:path_provider/path_provider.dart';
import 'package:flutter/material.dart';

class SelfieCameraWidget extends StatefulWidget {
  static SelfieCameraWidgetState of(BuildContext context) =>
      context.ancestorStateOfType(const TypeMatcher<SelfieCameraWidgetState>());

  @override
  State<StatefulWidget> createState() => new SelfieCameraWidgetState();
}

class SelfieCameraWidgetState extends State<SelfieCameraWidget> {
  List<CameraDescription> cameras;
  CameraController controller;
  bool isReady = false;
  bool noCameraDevice = false;
  int selectedCamera = 1;

  final GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>();

  @override
  void initState() {
    super.initState();
    _setupCamera();
  }

  Future<void> _setupCamera() async {
    try {
      // initialize cameras.
      cameras = await availableCameras();
      // initialize camera controllers.
      controller = new CameraController(
          cameras[selectedCamera], ResolutionPreset.medium
      );

      await controller.initialize();
    } on CameraException catch (_) {
      debugPrint("Some error occured!");
    }

    if (!mounted) {
      return;
    }

    setState(() {
      isReady = true;
    });
  }

  @override
  Widget build(BuildContext context) {
    if (controller == null || !controller.value.isInitialized) {
      return new Container();
    }
    return new AspectRatio(
        aspectRatio: controller.value.aspectRatio,
        child: new CameraPreview(controller));
  }

  String timestamp() => DateTime.now().millisecondsSinceEpoch.toString();

  void showInSnackBar(String message) {
    _scaffoldKey.currentState.showSnackBar(SnackBar(content: Text(message)));
  }

  void logError(String code, String message) =>
      print('Error: $code\nError Message: $message');

  void toggleCamera(){
    setState(() {
      selectedCamera = (selectedCamera == 1) ? 0: 1;
      _setupCamera();
    });
  }

  Future<String> takePicture() async {
    if (!controller.value.isInitialized) {
      showInSnackBar('Error: select a camera first.');
      return null;
    }
    final Directory extDir = await getApplicationDocumentsDirectory();
    final String dirPath = '${extDir.path}/Pictures/trekker_trek';
    await Directory(dirPath).create(recursive: true);
    final String filePath = '$dirPath/${timestamp()}.jpg';

    if (controller.value.isTakingPicture) {
      // A capture is already pending, do nothing.
      return null;
    }

    try {
      await controller.takePicture(filePath);
    } on CameraException catch (e) {
      _showCameraException(e);
      return null;
    }
    return filePath;
  }

  void _showCameraException(CameraException e) {
    logError(e.code, e.description);
    showInSnackBar('Error: ${e.code}\n${e.description}');
  }
}

Затем импортируйте его на правильный экран и вызовите SelfieCameraWidget()