getChildCount() return 0 in recyclerview

[fouriertry]

I need reset my recyclerview position when i refresh the adapter ,but the parcelable from onSaveInstanceState() in recyclerview return a wrong AnchorOffset, i find that getchildcount return 0 :

@Override
    public Parcelable onSaveInstanceState() {
        if (mPendingSavedState != null) {
            return new SavedState(mPendingSavedState);
        }
        SavedState state = new SavedState();
        if (getChildCount() > 0) {
            ensureLayoutState();
            boolean didLayoutFromEnd = mLastStackFromEnd ^ mShouldReverseLayout;
            state.mAnchorLayoutFromEnd = didLayoutFromEnd;
            if (didLayoutFromEnd) {
                final View refChild = getChildClosestToEnd();
                state.mAnchorOffset = mOrientationHelper.getEndAfterPadding()
                        - mOrientationHelper.getDecoratedEnd(refChild);
                state.mAnchorPosition = getPosition(refChild);
            } else {
                final View refChild = getChildClosestToStart();
                state.mAnchorPosition = getPosition(refChild);
                state.mAnchorOffset = mOrientationHelper.getDecoratedStart(refChild)
                        - mOrientationHelper.getStartAfterPadding();
            }
        } else {
            state.invalidateAnchor();
        }
        return state;
    }