Merge "Fixed an issue where the top edge flickered" into sc-dev am: 4f0d02b4c8

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/14964841

Change-Id: Ifc96bdbdbe4a441959d8cd817184562634aef299

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

@@ -224,8 +224,14 @@ public class AmbientState {
         return mScrollY;
     }
 
+    /**
+     * Set the new Scroll Y position.
+     */
     public void setScrollY(int scrollY) {
-        this.mScrollY = scrollY;
+        // Because we're dealing with an overscroller, scrollY could sometimes become smaller than
+        // 0. However this is only for internal purposes and the scroll position when read
+        // should never be smaller than 0, otherwise it can lead to flickers.
+        this.mScrollY = Math.max(scrollY, 0);
     }
 
     /**

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

@@ -1185,7 +1185,8 @@ public class NotificationStackScrollLayout extends ViewGroup implements Dumpable
     private void updateStackPosition(boolean listenerNeedsAnimation) {
         // Consider interpolating from an mExpansionStartY for use on lockscreen and AOD
         float endTopPosition = mTopPadding + mExtraTopInsetForFullShadeTransition
-                + mAmbientState.getOverExpansion();
+                + mAmbientState.getOverExpansion()
+                - getCurrentOverScrollAmount(false /* top */);
         final float fraction = mAmbientState.getExpansionFraction();
         final float stackY = MathUtils.lerp(0, endTopPosition, fraction);
         mAmbientState.setStackY(stackY);
@@ -1907,6 +1908,7 @@ public class NotificationStackScrollLayout extends ViewGroup implements Dumpable
             if (onTop) {
                 notifyOverscrollTopListener(amount, isRubberbanded);
             }
+            updateStackPosition();
             requestChildrenUpdate();
         }
     }

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

@@ -1071,10 +1071,6 @@ public class NotificationStackScrollLayoutController {
         mView.setAlpha(alpha);
     }
 
-    public float getCurrentOverScrollAmount(boolean top) {
-        return mView.getCurrentOverScrollAmount(top);
-    }
-
     public float calculateAppearFraction(float height) {
         return mView.calculateAppearFraction(height);
     }

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

@@ -218,13 +218,7 @@ public class StackScrollAlgorithm {
      */
     private void initAlgorithmState(ViewGroup hostView, StackScrollAlgorithmState state,
             AmbientState ambientState) {
-        float bottomOverScroll = ambientState.getOverScrollAmount(false /* onTop */);
+        state.scrollY = ambientState.getScrollY();
-        int scrollY = ambientState.getScrollY();
-
-        // Due to the overScroller, the stackscroller can have negative scroll state. This is
-        // already accounted for by the top padding and doesn't need an additional adaption
-        scrollY = Math.max(0, scrollY);
-        state.scrollY = (int) (scrollY + bottomOverScroll);
         state.mCurrentYPosition = -state.scrollY;
         state.mCurrentExpandedYPosition = -state.scrollY;
 
@@ -261,7 +255,7 @@ public class StackScrollAlgorithm {
         // Save the index of first view in shelf from when shade is fully
         // expanded. Consider updating these states in updateContentView instead so that we don't
         // have to recalculate in every frame.
-        float currentY = -scrollY;
+        float currentY = -ambientState.getScrollY();
         if (!ambientState.isOnKeyguard()) {
             currentY += mNotificationScrimPadding;
         }