diff --git a/ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactScrollView.java b/ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactScrollView.java index f10bd47ebbebb1..d39159a8b9de9b 100644 --- a/ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactScrollView.java +++ b/ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactScrollView.java @@ -309,8 +309,18 @@ public void getClippingRect(Rect outClippingRect) { @Override public void fling(int velocityY) { + // Workaround. + // On Android P if a ScrollView is inverted, we will get a wrong sign for + // velocityY (see https://issuetracker.google.com/issues/112385925). + // At the same time, mOnScrollDispatchHelper tracks the correct velocity direction. + // + // Hence, we can use the absolute value from whatever the OS gives + // us and use the sign of what mOnScrollDispatchHelper has tracked. + final int correctedVelocityY = (int)(Math.abs(velocityY) * Math.signum(mOnScrollDispatchHelper.getYFlingVelocity())); + + if (mPagingEnabled) { - flingAndSnap(velocityY); + flingAndSnap(correctedVelocityY); } else if (mScroller != null) { // FB SCROLLVIEW CHANGE @@ -326,7 +336,7 @@ public void fling(int velocityY) { getScrollX(), // startX getScrollY(), // startY 0, // velocityX - velocityY, // velocityY + correctedVelocityY, // velocityY 0, // minX 0, // maxX 0, // minY @@ -339,9 +349,9 @@ public void fling(int velocityY) { // END FB SCROLLVIEW CHANGE } else { - super.fling(velocityY); + super.fling(correctedVelocityY); } - handlePostTouchScrolling(0, velocityY); + handlePostTouchScrolling(0, correctedVelocityY); } private void enableFpsListener() {