[Bottom Sheet] Allow dragging the sheet on overscroll when draggableO…

…nNestedScroll=false

PiperOrigin-RevId: 624269903

lib/java/com/google/android/material/bottomsheet/BottomSheetBehavior.java

@@ -307,6 +307,7 @@ void onLayout(@NonNull View bottomSheet) {}
  private boolean draggable = true;
 
  private boolean draggableOnNestedScroll = true;
+ private boolean draggableOnNestedScrollLastDragIgnored;
 
  @State int state = STATE_COLLAPSED;
 
@@ -744,12 +745,14 @@ public void onNestedPreScroll(
  if (isNestedScrollingCheckEnabled() && target != scrollingChild) {
  return;
  }
- if (!draggableOnNestedScroll && target == scrollingChild) {
- return;
- }
  int currentTop = child.getTop();
  int newTop = currentTop - dy;
- if (dy > 0) { // Upward
+ if (dy > 0) { // Upward swipe
+ if (!draggableOnNestedScroll && target == scrollingChild && target.canScrollVertically(1)) {
+ // Prevent dragging if draggableOnNestedScroll=false and we can scroll the scrolling child.
+ draggableOnNestedScrollLastDragIgnored = true;
+ return;
+ }
  if (newTop < getExpandedOffset()) {
  consumed[1] = currentTop - getExpandedOffset();
  ViewCompat.offsetTopAndBottom(child, -consumed[1]);
@@ -764,8 +767,14 @@ public void onNestedPreScroll(
  ViewCompat.offsetTopAndBottom(child, -dy);
  setStateInternal(STATE_DRAGGING);
  }
- } else if (dy < 0) { // Downward
- if (!target.canScrollVertically(-1)) {
+ } else if (dy < 0) { // Downward swipe
+ boolean canScrollUp = target.canScrollVertically(-1);
+ if (!draggableOnNestedScroll && target == scrollingChild && canScrollUp) {
+ // Prevent dragging if draggableOnNestedScroll=false and we can scroll the scrolling child.
+ draggableOnNestedScrollLastDragIgnored = true;
+ return;
+ }
+ if (!canScrollUp) {
  if (newTop <= collapsedOffset || canBeHiddenByDragging()) {
  if (!draggable) {
  // Prevent dragging
@@ -785,6 +794,7 @@ public void onNestedPreScroll(
  dispatchOnSlide(child.getTop());
  lastNestedScrollDy = dy;
  nestedScrolled = true;
+ draggableOnNestedScrollLastDragIgnored = false;
  }
 
  @Override
@@ -885,7 +895,7 @@ public boolean onNestedPreFling(
 
  if (isNestedScrollingCheckEnabled() && nestedScrollingChildRef != null) {
  return target == nestedScrollingChildRef.get()
- && ((state != STATE_EXPANDED && draggableOnNestedScroll)
+ && ((state != STATE_EXPANDED && !draggableOnNestedScrollLastDragIgnored)
  || super.onNestedPreFling(coordinatorLayout, child, target, velocityX, velocityY));
  } else {
  return false;