How to implement video recorder in Camera2 API android?

public void startRecordingVideo() {
if (null == mCameraDevice || !mTextureView.isAvailable() || null == mPreviewSize) {
  return;
}
try {
  closePreviewSession();
  setUpMediaRecorder();
  SurfaceTexture texture = mTextureView.getSurfaceTexture();
  assert texture != null;
  texture.setDefaultBufferSize(mPreviewSize.getWidth(), mPreviewSize.getHeight());
  mPreviewBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_RECORD);
  List<Surface> surfaces = new ArrayList<>();
  /**
   * Surface for the camera preview set up
   */
  Surface previewSurface = new Surface(texture);
  surfaces.add(previewSurface);
  mPreviewBuilder.addTarget(previewSurface);
  //MediaRecorder setup for surface
  Surface recorderSurface = mMediaRecorder.getSurface();
  surfaces.add(recorderSurface);
  mPreviewBuilder.addTarget(recorderSurface);
  // Start a capture session
  mCameraDevice.createCaptureSession(surfaces, new CameraCaptureSession.StateCallback() {
    @Override
    public void onConfigured(@NonNull CameraCaptureSession cameraCaptureSession) {
      mPreviewSession = cameraCaptureSession;
      updatePreview();
      getActivity().runOnUiThread(() -> {
        mIsRecordingVideo = true;
        // Start recording
        mMediaRecorder.start();
      });
    }
    @Override
    public void onConfigureFailed(@NonNull CameraCaptureSession cameraCaptureSession) {
      Log.e(TAG, "onConfigureFailed: Failed");
    }
  }, mBackgroundHandler);
} catch (CameraAccessException | IOException e) {
  e.printStackTrace();
}

}

on this site there is an example with your question https://androidwave.com/video-recording-with-camera2-api-android/

The official basic video recording sample is here.