Document Loading Indicator

PdfViewer.uri may take long time to download PDF file and you want to show some loading indicator. You can do that by PdfViewerParams.loadingBannerBuilder:

loadingBannerBuilder: (context, bytesDownloaded, totalBytes) {
  return Center(
    child: CircularProgressIndicator(
      // totalBytes may not be available on certain case
      value: totalBytes != null ? bytesDownloaded / totalBytes : null,
      backgroundColor: Colors.grey,
    ),
  );
}