changecamera.dart

  void onNewCameraSelected(CameraDescription cameraDescription) async {
    if (controller != null) {
      await controller.dispose();
    }
    controller = CameraController(cameraDescription, ResolutionPreset.high);

    controller.addListener(() {
      if (mounted) setState(() {});
      if (controller.value.hasError) {
        showInSnackBar('Camera error ${controller.value.errorDescription}');
      }
    });

    try {
      await controller.initialize();
    } on CameraException catch (e) {
      showInSnackBar('Camera error ${e}');
    }

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