Making the detached scrollbar catch up faster to the actual scroll position.
Bug: 20035978
Change-Id: I4f9780e1c5c1d10a7956ece729163544d79d72c3
diff --git a/src/com/android/launcher3/allapps/AllAppsRecyclerView.java b/src/com/android/launcher3/allapps/AllAppsRecyclerView.java
index 5ec8bb2..1cde7bf 100644
--- a/src/com/android/launcher3/allapps/AllAppsRecyclerView.java
+++ b/src/com/android/launcher3/allapps/AllAppsRecyclerView.java
@@ -267,8 +267,18 @@
int diffScrollY = scrollBarY - thumbScrollY;
if (diffScrollY * dy > 0f) {
// User is scrolling in the same direction the thumb needs to catch up to the
- // current scroll position.
- thumbScrollY += dy < 0 ? Math.max(dy, diffScrollY) : Math.min(dy, diffScrollY);
+ // current scroll position. We do this by mapping the difference in movement
+ // from the original scroll bar position to the difference in movement necessary
+ // in the detached thumb position to ensure that both speed towards the same
+ // position at either end of the list.
+ if (dy < 0) {
+ int offset = (int) ((dy * thumbScrollY) / (float) scrollBarY);
+ thumbScrollY += Math.max(offset, diffScrollY);
+ } else {
+ int offset = (int) ((dy * (availableScrollBarHeight - thumbScrollY)) /
+ (float) (availableScrollBarHeight - scrollBarY));
+ thumbScrollY += Math.min(offset, diffScrollY);
+ }
thumbScrollY = Math.max(0, Math.min(availableScrollBarHeight, thumbScrollY));
mScrollbar.setThumbOffset(scrollBarX, thumbScrollY);
if (scrollBarY == thumbScrollY) {