Android recyclerView横条指示器实现淘宝菜单模块

<RelativeLayout
  android:id="@ id/parent_layout"
  android:layout_marginTop="10dp"
  android:layout_width="80dp"
  android:layout_height="4dp"
  android:layout_gravity="center"
  android:background="@drawable/bg_store_classify_normal">

  <View
   android:id="@ id/main_line"
   android:layout_width="40dp"
   android:layout_height="4dp"
   android:layout_centerVertical="true"
   android:background="@drawable/bg_store_classify_selected" />
</RelativeLayout>

rcvClassifyTypes.addOnScrollListener(new RecyclerView.OnScrollListener() {
 @Override
 public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
  super.onScrollStateChanged(recyclerView, newState);
 
 }
 
 @Override
 public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
  super.onScrolled(recyclerView, dx, dy);
  //整体的总宽度，注意是整体，包括在显示区域之外的
  //滚动条表示的总范围
  int temp = rcvClassifyTypes.computeHorizontalScrollRange();
  if (temp > range) {
   range = temp;
  }
  //滑块的偏移量
  int offset = rcvClassifyTypes.computeHorizontalScrollOffset();
  //可视区域长度
  int extent = rcvClassifyTypes.computeHorizontalScrollExtent();
  //滑出部分在剩余范围的比例
  float proportion = (float) (offset * 1.0 / (range - extent));
  //计算滚动条宽度
  float transMaxRange = parentLayout.getWidth() - childline.getWidth();
  //设置滚动条移动
  childline.setTranslationX(transMaxRange * proportion);
 }
});