Attempt to invoke virtual method 'int android.hardware.camera2.CameraCaptureSession.capture(android.hardware.camera2.CaptureRequest, android.hardware.camera2.CameraCaptureSession$CaptureCallback, android.os.Handler)' on a null object reference

main.dart

import 'dart:io';

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

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatelessWidget {
  MyHomePage({Key key, this.title}) : super(key: key);
  final String title;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(title),
      ),
      body: Center(
        child: new Camera(),
      ),
    );
  }
}

class Camera extends StatefulWidget {
  @override
  State<Camera> createState() => new _CameraState();
}

class _CameraState extends State<Camera> {
  CameraController _controller;
  List<CameraDescription> _cameras;

  bool _runningErrorCreation = false;
  int _count;

  void _runErrorCreation() async {
    if (!_runningErrorCreation) {
      _count = 0;
      _runningErrorCreation = true;
      while (await _startImageStream()) {}
      _runningErrorCreation = false;
    }
  }

  Future<bool> _startImageStream() async {
    _count++;
    try {
      Directory dir = await getTemporaryDirectory();
      String path = join(dir.path, "capture.jpg");
      File img = new File(path);
      if (await img.exists()) {
        await img.delete();
      }

      await _controller.startImageStream((_) {});
      await _controller.stopImageStream();
      await _controller.takePicture(path);
      return true;
    } catch (e) {
      debugPrint(e.toString());
      debugPrint("Times ran before error occurred: $_count");
      return false;
    }
  }

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

    _getCameras().then((_) {
      _initialise();
    });
  }

  Future<void> _getCameras() async {
    _cameras = await availableCameras();
  }

  Future<void> _initialise() async {
    if (_cameras.isEmpty) {
      setState(() {});
      return;
    }

    CameraDescription camera;
    for (int i = 0; i < _cameras.length; i++) {
      if (_cameras[i].lensDirection == CameraLensDirection.front) {
        camera = _cameras[i];
        break;
      }
    }

    if (camera == null) {
      // In the case cameras for the given direction were found
      camera = _cameras[0];
    }

    _controller = new CameraController(camera, ResolutionPreset.low);
    await _controller.initialize();

    if (!mounted) return;
    setState(() {});
  }

  bool get isInitialised {
    return _controller != null && _controller.value.isInitialized;
  }

  Widget get contents {
    if (_cameras != null && _cameras.isEmpty) {
      return new Center(
        child: new Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            new Text(
              "No cameras found...",
            ),
            new Text(
              "Check that you are using a device with connected cameras.",
            ),
          ],
        ),
      );
    }

    if (!isInitialised) {
      return Container();
    }

    return new AspectRatio(
      aspectRatio: _controller.value.aspectRatio,
      child: CameraPreview(_controller),
    );
  }

  Widget build(BuildContext context) {
    return new GestureDetector(
      onTap: _runErrorCreation,
      child: contents,
    );
  }
}

pubspec.yaml

name: tst
description: A new Flutter project.

version: 1.0.0+1

environment:
  sdk: ">=2.1.0 <3.0.0"

dependencies:
  flutter:
    sdk: flutter
  cupertino_icons: ^0.1.2
  camera: 0.3.0+3
  path_provider: ^0.4.1

dev_dependencies:
  flutter_test:
    sdk: flutter

flutter:
  uses-material-design: true