Camera orientation

import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:camera/camera.dart';
import 'package:flutter/services.dart';

class CameraView extends StatefulWidget {
  @override
  _CameraViewState createState() => _CameraViewState();
}

class _CameraViewState extends State<CameraView> {
  CameraController _cameraController;
  bool _isLoading;

  void _initializeCamera() async {
    setState(() {
      _isLoading = true;
    });

    final List<CameraDescription> cameras = await availableCameras();
    final CameraDescription description = cameras.firstWhere(
        (camera) => camera.lensDirection == CameraLensDirection.back);

    _cameraController = CameraController(
      description,
      defaultTargetPlatform == TargetPlatform.iOS
          ? ResolutionPreset.low
          : ResolutionPreset.medium,
      enableAudio: false,
    );

    await _cameraController.initialize();
    setState(() {
      _isLoading = false;
    });
  }

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

    SystemChrome.setEnabledSystemUIOverlays(<SystemUiOverlay>[]);
    SystemChrome.setPreferredOrientations(
      <DeviceOrientation>[DeviceOrientation.landscapeLeft],
    );

    _initializeCamera();
  }

  @override
  void dispose() {
    _cameraController.dispose().then((_) {
      // Caso precise desativare alguma coisa interno na camera
    });

    SystemChrome.setPreferredOrientations(<DeviceOrientation>[]);
    SystemChrome.setEnabledSystemUIOverlays(<SystemUiOverlay>[
      SystemUiOverlay.top,
      SystemUiOverlay.bottom,
    ]);

    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    final Size querySizes = MediaQuery.of(context).size;
    final double captureHeight = 144;
    final double vSpacing = (querySizes.height - captureHeight) / 2;
    final double hSpacing = 30;
    final Color overlayColor = Colors.green.withOpacity(0.3);

    return Material(
      child: _isLoading
          ? Center(
              child: Text(
                "Iniciando Câmera...",
                style: TextStyle(
                  color: Colors.green,
                  fontSize: 30,
                ),
              ),
            )
          : Stack(
              alignment: FractionalOffset.center,
              children: <Widget>[
                Positioned.fill(
                  child: AspectRatio(
                    aspectRatio: _cameraController.value.aspectRatio,
                    child: CameraPreview(_cameraController),
                  ),
                ),
                Column(
                  children: <Widget>[
                    Container(
                      height: vSpacing,
                      width: double.infinity,
                      color: overlayColor,
                    ),
                    Row(
                      mainAxisAlignment: MainAxisAlignment.center,
                      children: <Widget>[
                        Container(
                          width: hSpacing,
                          height: captureHeight,
                          color: overlayColor,
                        ),
                        Expanded(
                          child: Container(
                            alignment: Alignment.center,
                            height: captureHeight,
                            decoration: BoxDecoration(
                              border: Border.all(
                                width: 2,
                                color: Colors.white.withGreen(255),
                              ),
                              // borderRadius: BorderRadius.circular(6),
                              color: Colors.white.withOpacity(0),
                            ),
                          ),
                        ),
                        Container(
                          width: hSpacing,
                          height: captureHeight,
                          color: overlayColor,
                        ),
                      ],
                    ),
                    Container(
                      height: vSpacing,
                      width: double.infinity,
                      color: overlayColor,
                    ),
                  ],
                ),
              ],
            ),
    );
  }
}