[BottomSheet] Fix activity leak when setting states on destroying activities

The activity leak can happen in a corner case: setting bottom sheet state when the bottom sheet is dismissed and the host activity is closed. In this situation SettleRunnable will be posted to ViewRootImpl since the bottom sheet is not attached, which leaves references of the dismissed bottom sheet (and thus the destroyed activity) in ViewRootImpl and causes activity leak.

Fixes this by using weak reference in SettleRunnable instead of the strong reference, which is the standard practice of the BottomSheetBehavior class.

Resolves #1417

PiperOrigin-RevId: 430709002

Author: drchen

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

@@ -1592,7 +1592,7 @@ void startSettlingAnimation(
         settleRunnable = new SettleRunnable(child, state);
       }
       // If the SettleRunnable has not been posted, post it with the correct state.
-      if (settleRunnable.isPosted == false) {
+      if (!settleRunnable.isPosted) {
         settleRunnable.targetState = state;
         ViewCompat.postOnAnimation(child, settleRunnable);
         settleRunnable.isPosted = true;
@@ -1890,21 +1890,23 @@ public int getLastStableState() {
 
   private class SettleRunnable implements Runnable {
 
-    private final View view;
+    private final WeakReference<View> viewRef;
 
     private boolean isPosted;
 
     @State int targetState;
 
     SettleRunnable(View view, @State int targetState) {
-      this.view = view;
+      this.viewRef = new WeakReference<>(view);
       this.targetState = targetState;
     }
 
     @Override
     public void run() {
-      if (viewDragHelper != null && viewDragHelper.continueSettling(true)) {
-        ViewCompat.postOnAnimation(view, this);
+      if (viewRef.get() != null
+          && viewDragHelper != null
+          && viewDragHelper.continueSettling(true)) {
+        ViewCompat.postOnAnimation(viewRef.get(), this);
       } else {
         setStateInternal(targetState);
       }