iOS8 : Custom Keyboard - Open Camera with AVCaptureVideoPreviewLayer in the background of keyboard

Question

It is posible to open AVCaptureVideoPreviewLayer in the background of iOS8 Custom keyboard ? I tried with this code

    AVCaptureSession *session = [[AVCaptureSession alloc] init];
AVCaptureDevice *videoDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
if (videoDevice)
{
    NSError *error;
    AVCaptureDeviceInput *videoInput = [AVCaptureDeviceInput deviceInputWithDevice:videoDevice error:&error];
    if (!error)
    {
        if ([session canAddInput:videoInput])
        {
            [session addInput:videoInput];
            AVCaptureVideoPreviewLayer *previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:session];
            previewLayer.frame = self.bounds;
            NSLog(@"open %@",NSStringFromCGRect(self.bounds));
            [self.camView.layer addSublayer:previewLayer];
            [session startRunning];
        }
    }
}

It is ask for permission to use camera but not open camera in background of keyboard. Please help me. Thanks.