Future<void> main() async {
  // Ensure that plugin services are initialized so that
  // `availableCameras()` can be called before `runApp().
  WidgetsFlutterBinding.ensureInitialized();
  
  // Obtain a list of the available cameras on the device.
  List<CameraDescription> cameras = await availableCameras();

  // Get a specific camera from the list of available cameras.
  final firstCamera = cameras.first;

  runApp(
    MaterialApp(
      theme: ThemeData.dark(),
      home: CameraApp(
        // Pass the appropriate camera to the CameraApp widget.
        camera: firstCamera,
      ),
    ),
  );
}

class CameraApp extends StatefulWidget {

  final CameraDescription camera;

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

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

class _CameraAppState extends State<CameraApp> {
  CameraController controller;

  @override
  void initState() {
    super.initState();
    controller = CameraController(widget.camera, 
    	ResolutionPreset.medium);
    controller.initialize().then((_) {
      // do nothing if state has already been disposed
      if (!mounted) {
        return;
      }
      setState(() {});
    });
  }

  @override
  void dispose() {
    controller?.dispose();
    super.dispose();
  }
}

  @override
  Widget build(BuildContext context) {
    if (!controller.value.isInitialized) {
      return Container();
    }
    return Scaffold(
      backgroundColor: Theme.of(context).backgroundColor,
      extendBody: true,
      bottomNavigationBar: _buildBottomNavigationBar(),
      body: _buildCameraPreview(),
    );
  }

  Widget _buildCameraPreview() {
    // get screen aspect ratio
    final size = MediaQuery.of(context).size;
    return Container(
      child: Transform.scale(
        scale: controller.value.aspectRatio / size.aspectRatio,
        child: Center(
          child: AspectRatio(
            aspectRatio: controller.value.aspectRatio,
            child: CameraPreview(controller),
          ),
        ),
      ),
    );
  }

  Widget _buildBottomNavigationBar() {
    return Container(
      color: Theme.of(context).bottomAppBarColor,
      height: 100.0,
      width: double.infinity,
      child: Row(
        mainAxisAlignment: MainAxisAlignment.spaceAround,
        children: <Widget>[
          CircleAvatar(
            backgroundColor: Colors.white,
            radius: 28.0,
            child: IconButton(
              icon: Icon(
                Icons.camera_alt,
                size: 28.0,
                color: Colors.black,
              ),
              onPressed: () async {
                _captureImage();
              }
            ),
          ),
        ],
      ),
    );
  }

  void _captureImage() async {
    if (controller.value.isInitialized) {
      // getExternalStorageDirectory() comes from the path_provider plugin 
      // which exposes commonly used filesystem locations
      final Directory extDir = await getExternalStorageDirectory();
      final String dirPath = '${extDir.path}/media';
      await Directory(dirPath).create(recursive: true);
      final String filePath = '$dirPath/${_timestamp()}.jpeg';
      print("filePath: $filePath");
      await controller.takePicture(filePath);
      setState(() {});
      Navigator.push(
        context,
        MaterialPageRoute(
          builder: (context) => DisplayPictureScreen(imagePath: filePath),
        ),
      );
    }
  }
  
  String _timestamp() => DateTime.now().millisecondsSinceEpoch.toString();
  

class DisplayPictureScreen extends StatelessWidget {
  final String imagePath;

  const DisplayPictureScreen({Key key, this.imagePath}) : super(key: key);

  @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: Center(
          child: Image.file(File(imagePath))
      ),
    );
  }
}