Update BottomSheet to have a singular SettleRunnable

Resolves #516

PiperOrigin-RevId: 283802793
(cherry picked from commit e057829)

Author: melaniegoetz

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

@@ -207,6 +207,8 @@ public abstract static class BottomSheetCallback {
 
   private boolean isShapeExpanded;
 
+  private SettleRunnable settleRunnable = null;
+
   @Nullable private ValueAnimator interpolatorAnimator;
 
   private static final int DEF_STYLE_RES = R.style.Widget_Design_BottomSheet_Modal;
@@ -1181,7 +1183,19 @@ void startSettlingAnimation(View child, int state, int top, boolean settleFromVi
       setStateInternal(STATE_SETTLING);
       // STATE_SETTLING won't animate the material shape, so do that here with the target state.
       updateDrawableForTargetState(state);
-      ViewCompat.postOnAnimation(child, new SettleRunnable(child, state));
+      if (settleRunnable == null) {
+        // If the singleton SettleRunnable instance has not been instantiated, create it.
+        settleRunnable = new SettleRunnable(child, state);
+      }
+      // If the SettleRunnable has not been posted, post it with the correct state.
+      if (settleRunnable.isPosted == false) {
+        settleRunnable.targetState = state;
+        ViewCompat.postOnAnimation(child, settleRunnable);
+        settleRunnable.isPosted = true;
+      } else {
+        // Otherwise, if it has been posted, just update the target state.
+        settleRunnable.targetState = state;
+      }
     } else {
       setStateInternal(state);
     }
@@ -1356,7 +1370,9 @@ private class SettleRunnable implements Runnable {
 
     private final View view;
 
-    @State private final int targetState;
+    private boolean isPosted;
+
+    @State int targetState;
 
     SettleRunnable(View view, @State int targetState) {
       this.view = view;
@@ -1368,10 +1384,9 @@ public void run() {
       if (viewDragHelper != null && viewDragHelper.continueSettling(true)) {
         ViewCompat.postOnAnimation(view, this);
       } else {
-        if (state == STATE_SETTLING) {
-          setStateInternal(targetState);
-        }
+        setStateInternal(targetState);
       }
+      this.isPosted = false;
     }
   }
 

tests/javatests/com/google/android/material/bottomsheet/BottomSheetBehaviorTest.java

@@ -78,6 +78,7 @@ public static class Callback extends BottomSheetBehavior.BottomSheetCallback
       implements IdlingResource {
 
     private boolean isIdle;
+    private boolean idleWhileSettling;
 
     private IdlingResource.ResourceCallback resourceCallback;
 
@@ -117,9 +118,13 @@ public void registerIdleTransitionCallback(ResourceCallback callback) {
       resourceCallback = callback;
     }
 
+    public void setIdleWhileSettling(boolean idleWhileSettling) {
+      this.idleWhileSettling = idleWhileSettling;
+    }
+
     private boolean isIdleState(int state) {
       return state != BottomSheetBehavior.STATE_DRAGGING
-          && state != BottomSheetBehavior.STATE_SETTLING;
+          && (idleWhileSettling || state != BottomSheetBehavior.STATE_SETTLING);
     }
   }