camera.dart

void onTakePictureButtonPressed() {
    takePicture().then((String filePath) {
      if (mounted) {
        setState(() {
          showCamera = false;
          imagePath = filePath;
        });
      }
    });
  }

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

    if (controller.value.isTakingPicture) {
      return null;
    }

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