item高度不同时Recyclerview获取滑动距离的方法

private int totalDy = 0;
mRecycler.addOnScrollListener(new RecyclerView.OnScrollListener() {
  @Override
  public void onScrolled(RecyclerView recyclerview, int dx, int dy) {
    totalDy -= dy;
  }
}

private Map<Integer, Integer> heightMap = new HashMap<>();
int count = getChildCount();
for (int i = 0; i < count; i++) {
  View view = getChildAt(i);
  heightMap.put(i, view.getHeight());
}

@Override
public int computeVerticalScrollOffset(RecyclerView.State state) {
  if (getChildCount() == 0) {
    return 0;
  }
  int firstVisiablePosition = findFirstVisibleItemPosition();
  View firstVisiableView = findViewByPosition(firstVisiablePosition);
  int offsetY = -(int) (firstVisiableView.getY());
  for (int i = 0; i < firstVisiablePosition; i++) {
    offsetY += heightMap.get(i) == null ? 0 : heightMap.get(i);
  }
  return offsetY;
}

public class OffsetLinearLayoutManager extends LinearLayoutManager {

  public OffsetLinearLayoutManager(Context context) {
    super(context);
  }

  private Map<Integer, Integer> heightMap = new HashMap<>();

  @Override
  public void onLayoutCompleted(RecyclerView.State state) {
    super.onLayoutCompleted(state);
    int count = getChildCount();
    for (int i = 0; i < count ; i++) {
      View view = getChildAt(i);
      heightMap.put(i, view.getHeight());
    }
  }

  @Override
  public int computeVerticalScrollOffset(RecyclerView.State state) {
    if (getChildCount() == 0) {
      return 0;
    }
    try {
      int firstVisiablePosition = findFirstVisibleItemPosition();
      View firstVisiableView = findViewByPosition(firstVisiablePosition);
      int offsetY = -(int) (firstVisiableView.getY());
      for (int i = 0; i < firstVisiablePosition; i++) {
        offsetY += heightMap.get(i) == null ? 0 : heightMap.get(i);
      }
      return offsetY;
    } catch (Exception e) {
      return 0;
    }
  }
}

mRecycler.setLayoutManager(new OffsetLinearLayoutManager(mContext));