Fix notification launch animation for groups

This fixes a problem where the z ordering is not correct during the launch animation of a child notification inside a notification group. The launched notification was rendered below other notifications in some cases.

Test: Manual, i.e. posting various types of notifications and analyzing the animations in screenrecordings.
Bug: 246932690
Change-Id: I658b4b3db75da5199b7b7cb416b7d7fabbc75520

packages/SystemUI/src/com/android/systemui/statusbar/notification/row/ExpandableNotificationRow.java

@@ -976,10 +976,10 @@ public class ExpandableNotificationRow extends ActivatableNotificationView
     /**
      * Updates states of all children.
      */
-    public void updateChildrenStates(AmbientState ambientState) {
+    public void updateChildrenStates() {
         if (mIsSummaryWithChildren) {
             ExpandableViewState parentState = getViewState();
-            mChildrenContainer.updateState(parentState, ambientState);
+            mChildrenContainer.updateState(parentState);
         }
     }
 

packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/NotificationChildrenContainer.java

@@ -616,9 +616,8 @@ public class NotificationChildrenContainer extends ViewGroup
      * Update the state of all its children based on a linear layout algorithm.
      *
      * @param parentState  the state of the parent
-     * @param ambientState the ambient state containing ambient information
      */
-    public void updateState(ExpandableViewState parentState, AmbientState ambientState) {
+    public void updateState(ExpandableViewState parentState) {
         int childCount = mAttachedChildren.size();
         int yPosition = mNotificationHeaderMargin + mCurrentHeaderTranslation;
         boolean firstChild = true;
@@ -661,9 +660,17 @@ public class NotificationChildrenContainer extends ViewGroup
             childState.height = intrinsicHeight;
             childState.setYTranslation(yPosition + launchTransitionCompensation);
             childState.hidden = false;
-            // When the group is expanded, the children cast the shadows rather than the parent
-            // so use the parent's elevation here.
-            if (childrenExpandedAndNotAnimating && mEnableShadowOnChildNotifications) {
+            if (child.isExpandAnimationRunning() || mContainingNotification.hasExpandingChild()) {
+                // Not modifying translationZ during launch animation. The translationZ of the
+                // expanding child is handled inside ExpandableNotificationRow and the translationZ
+                // of the other children inside the group should remain unchanged. In particular,
+                // they should not take over the translationZ of the parent, since the parent has
+                // a positive translationZ set only for the expanding child to be drawn above other
+                // notifications.
+                childState.setZTranslation(child.getTranslationZ());
+            } else if (childrenExpandedAndNotAnimating && mEnableShadowOnChildNotifications) {
+                // When the group is expanded, the children cast the shadows rather than the parent
+                // so use the parent's elevation here.
                 childState.setZTranslation(parentState.getZTranslation());
             } else {
                 childState.setZTranslation(0);
@@ -716,9 +723,15 @@ public class NotificationChildrenContainer extends ViewGroup
                 mHeaderViewState = new ViewState();
             }
             mHeaderViewState.initFrom(mNotificationHeader);
-            mHeaderViewState.setZTranslation(childrenExpandedAndNotAnimating
-                    ? parentState.getZTranslation()
-                    : 0);
+
+            if (mContainingNotification.hasExpandingChild()) {
+                // Not modifying translationZ during expand animation.
+                mHeaderViewState.setZTranslation(mNotificationHeader.getTranslationZ());
+            } else if (childrenExpandedAndNotAnimating) {
+                mHeaderViewState.setZTranslation(parentState.getZTranslation());
+            } else {
+                mHeaderViewState.setZTranslation(0);
+            }
             mHeaderViewState.setYTranslation(mCurrentHeaderTranslation);
             mHeaderViewState.setAlpha(mHeaderVisibleAmount);
             // The hiding is done automatically by the alpha, otherwise we'll pick it up again

packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/StackScrollAlgorithm.java

@@ -128,7 +128,7 @@ public class StackScrollAlgorithm {
         updateSpeedBumpState(algorithmState, speedBumpIndex);
         updateShelfState(algorithmState, ambientState);
         updateAlphaState(algorithmState, ambientState);
-        getNotificationChildrenStates(algorithmState, ambientState);
+        getNotificationChildrenStates(algorithmState);
     }
 
     private void updateAlphaState(StackScrollAlgorithmState algorithmState,
@@ -231,14 +231,13 @@ public class StackScrollAlgorithm {
         }
     }
 
-    private void getNotificationChildrenStates(StackScrollAlgorithmState algorithmState,
-                                               AmbientState ambientState) {
+    private void getNotificationChildrenStates(StackScrollAlgorithmState algorithmState) {
         int childCount = algorithmState.visibleChildren.size();
         for (int i = 0; i < childCount; i++) {
             ExpandableView v = algorithmState.visibleChildren.get(i);
             if (v instanceof ExpandableNotificationRow) {
                 ExpandableNotificationRow row = (ExpandableNotificationRow) v;
-                row.updateChildrenStates(ambientState);
+                row.updateChildrenStates();
             }
         }
     }