[Catalog][Carousel] Update slider position when carousel is scrolled in uncontained carousel demo

Resolves #3539

GIT_ORIGIN_REV_ID=c520f2f5fa88a9c08e65e9d3e34db075fdb938dd
PiperOrigin-RevId: 560815648

Author: manabu-nakamura

catalog/java/io/material/catalog/carousel/UncontainedCarouselDemoFragment.java

@@ -103,8 +103,31 @@ public void onViewCreated(@NonNull View view, @Nullable Bundle bundle) {
 
     CarouselAdapter adapter =
         new CarouselAdapter(
-            (item, position) -> uncontainedRecyclerView.scrollToPosition(position),
+            (item, position) -> {
+              uncontainedRecyclerView.scrollToPosition(position);
+              positionSlider.setValue(position + 1);
+            },
             R.layout.cat_carousel_item_narrow);
+    uncontainedRecyclerView.addOnScrollListener(
+        new RecyclerView.OnScrollListener() {
+          private boolean dragged = false;
+
+          @Override
+          public void onScrollStateChanged(@NonNull RecyclerView recyclerView, int newState) {
+            if (newState == RecyclerView.SCROLL_STATE_DRAGGING) {
+              dragged = true;
+            } else if (dragged && newState == RecyclerView.SCROLL_STATE_IDLE) {
+              if (recyclerView.computeHorizontalScrollRange() != 0) {
+                positionSlider.setValue(
+                    (adapter.getItemCount() - 1)
+                        * recyclerView.computeHorizontalScrollOffset()
+                        / recyclerView.computeHorizontalScrollRange()
+                        + 1);
+              }
+              dragged = false;
+            }
+          }
+        });
 
     itemCountDropdown.setOnItemClickListener(
         (parent, view1, position, id) ->