void InitThumbnailGridAndButton() { thumbnailGrid = FindViewById <PdfThumbnailGrid> (Resource.Id.thumbnailGrid); if (thumbnailGrid == null) { throw new IllegalStateException("Error while loading CustomFragmentActivity. The example layout was missing the thumbnail grid view."); } thumbnailGrid.PageClick += (sender, e) => { fragment.PageIndex = e.P1; (sender as PdfThumbnailGrid)?.Hide(); }; // The thumbnail grid is hidden by default. Set up a click listener to show it. var openTumbnailGridButton = FindViewById <ImageView> (Resource.Id.openThumbnailGridButton); openTumbnailGridButton.Click += (sender, e) => thumbnailGrid.Show(); openTumbnailGridButton.SetImageDrawable(TintDrawable(openTumbnailGridButton.Drawable, ContextCompat.GetColor(this, Resource.Color.pspdf__color_white))); }