Android 如何仅在滚动时在项目之间添加空间

我有水平循环视图，显示在全屏上。 这是我的活动布局：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/photos_list"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</RelativeLayout>

在屏幕截图上，我展示了我想要的空间：

---

要获得此空间，应使用DividerItemDecoration。您可以设置它的宽度和颜色。比如说,

可提取：

或者在回收机闲置时，像这样移除

recyclerView.removeItemDecoration(dividerItemDecoration);

要检测回收器是否正在滚动，请实现RecyclerView.OnScrollListener

RecyclerView photoList = findViewById(R.id.photos_list);
        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this, RecyclerView.HORIZONTAL, false);
        photoList.setLayoutManager(linearLayoutManager);


        PagerSnapHelper pagerSnapHelper = new PagerSnapHelper();
        pagerSnapHelper.attachToRecyclerView(photoList);

        PhotoListAdapter photoListAdapter = new PhotoListAdapter(this, photoResults);
        photoList.setAdapter(photoListAdapter);

 <shape xmlns:android="http://schemas.android.com/apk/res/android"
           android:shape="rectangle">
        <size
            android:width="1dp"
            android:height="1dp" />
        <solid android:color="@color/primary" />
    </shape>

DividerItemDecoration dividerItemDecoration = new DividerItemDecoration(getContext(),
                    LinearLayoutManager.VERTICAL);//or HORIZONTAL
dividerItemDecoration.setDrawable(getContext().getResources().getDrawable(R.drawable.sk_line_divider));
recyclerView.addItemDecoration(dividerItemDecoration);

recyclerView.removeItemDecoration(dividerItemDecoration);