如何在Flutter/Dart中访问摄像头本身？

dependencies:
  camera: ^0.9.4+5

import 'package:camera/camera.dart';

List<CameraDescription> cameras;

Future<void> initCamera() async {
  cameras = await availableCameras();
}

CameraController controller;

Future<void> openCamera() async {
  controller = CameraController(cameras[0], ResolutionPreset.medium);
  await controller.initialize();
  await controller.startPreview();
}

Widget build(BuildContext context) {
  return Scaffold(
    body: Center(
      child: AspectRatio(
        aspectRatio: controller.value.aspectRatio,
        child: CameraPreview(controller),
      ),
    ),
  );
}