Yqritc的回答非常适合我。我用的是Kotlin，这里有一个等价物。

class ItemOffsetDecoration : RecyclerView.ItemDecoration  {

    // amount to add to padding
    private val _itemOffset: Int

    constructor(itemOffset: Int) {
        _itemOffset = itemOffset
    }

    constructor(@NonNull context: Context, @DimenRes itemOffsetId: Int){
       _itemOffset = context.resources.getDimensionPixelSize(itemOffsetId)
    }

    /**
     * Applies padding to all sides of the [Rect], which is the container for the view
     */
    override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView,state: RecyclerView.State) {
        super.getItemOffsets(outRect, view, parent, state)
        outRect.set(_itemOffset, _itemOffset, _itemOffset, _itemOffset)
    }
}

其他一切都是一样的。

复制@edwardaa提供的代码，我使它完美地支持RTL:

public class GridSpacingItemDecoration extends RecyclerView.ItemDecoration {
    private int spanCount;
    private int spacing;
    private boolean includeEdge;
    private int headerNum;
    private boolean isRtl = TextUtilsCompat.getLayoutDirectionFromLocale(Locale.getDefault()) == ViewCompat.LAYOUT_DIRECTION_RTL;

    public GridSpacingItemDecoration(int spanCount, int spacing, boolean includeEdge, int headerNum) {
        this.spanCount = spanCount;
        this.spacing = spacing;
        this.includeEdge = includeEdge;
        this.headerNum = headerNum;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        int position = parent.getChildAdapterPosition(view) - headerNum; // item position
        if (position >= 0) {
            int column = position % spanCount; // item column
            if(isRtl) {
                column = spanCount - 1 - column;
            }
            if (includeEdge) {
                outRect.left = spacing - column * spacing / spanCount; // spacing - column * ((1f / spanCount) * spacing)
                outRect.right = (column + 1) * spacing / spanCount; // (column + 1) * ((1f / spanCount) * spacing)

                if (position < spanCount) { // top edge
                    outRect.top = spacing;
                }
                outRect.bottom = spacing; // item bottom
            } else {
                outRect.left = column * spacing / spanCount; // column * ((1f / spanCount) * spacing)
                outRect.right = spacing - (column + 1) * spacing / spanCount; // spacing - (column + 1) * ((1f /    spanCount) * spacing)
                if (position >= spanCount) {
                    outRect.top = spacing; // item top
                }
            }
        } else {
            outRect.left = 0;
            outRect.right = 0;
            outRect.top = 0;
            outRect.bottom = 0;
        }
    }
}

这也适用于RecyclerView with header。

public class GridSpacingItemDecoration extends RecyclerView.ItemDecoration {

    private int spanCount;
    private int spacing;
    private boolean includeEdge;
    private int headerNum;

    public GridSpacingItemDecoration(int spanCount, int spacing, boolean includeEdge, int headerNum) {
        this.spanCount = spanCount;
        this.spacing = spacing;
        this.includeEdge = includeEdge;
        this.headerNum = headerNum;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        int position = parent.getChildAdapterPosition(view) - headerNum; // item position

        if (position >= 0) {
            int column = position % spanCount; // item column

            if (includeEdge) {
                outRect.left = spacing - column * spacing / spanCount; // spacing - column * ((1f / spanCount) * spacing)
                outRect.right = (column + 1) * spacing / spanCount; // (column + 1) * ((1f / spanCount) * spacing)

                if (position < spanCount) { // top edge
                    outRect.top = spacing;
                }
                outRect.bottom = spacing; // item bottom
            } else {
                outRect.left = column * spacing / spanCount; // column * ((1f / spanCount) * spacing)
                outRect.right = spacing - (column + 1) * spacing / spanCount; // spacing - (column + 1) * ((1f /    spanCount) * spacing)
                if (position >= spanCount) {
                    outRect.top = spacing; // item top
                }
            }
        } else {
            outRect.left = 0;
            outRect.right = 0;
            outRect.top = 0;
            outRect.bottom = 0;
        }
    }
    }
}

如果你有一个在列表和网格之间切换的拨动开关，不要忘记在设置任何新的项目装饰之前调用recyclerView.removeItemDecoration(..)。如果不是这样，那么新的间隔计算将是不正确的。

就像这样:

recyclerView.removeItemDecoration(gridItemDecorator)
recyclerView.removeItemDecoration(listItemDecorator)

if (showAsList) {
    recyclerView.layoutManager = LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false)
    recyclerView.addItemDecoration(listItemDecorator)
} else {
    recyclerView.layoutManager = GridLayoutManager(this, spanCount)
    recyclerView.addItemDecoration(gridItemDecorator)
}

我根据edwardaa的回答做了一个Kotlin版本

class RecyclerItemDecoration(private val spanCount: Int, private val spacing: Int) : RecyclerView.ItemDecoration() {

  override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State) {

    val spacing = Math.round(spacing * parent.context.resources.displayMetrics.density)
    val position = parent.getChildAdapterPosition(view)
    val column = position % spanCount

    outRect.left = spacing - column * spacing / spanCount
    outRect.right = (column + 1) * spacing / spanCount

    outRect.top = if (position < spanCount) spacing else 0
    outRect.bottom = spacing
  }

}

确保你在gradle模块中实现了这个:

implementation 'com.github.grzegorzojdana:SpacingItemDecoration:1.1.0'

创建这个简单的函数:

public static int dpToPx(Context c, int dp) {
    Resources r = c.getResources();
    return Math.round(TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dp, r.getDisplayMetrics()));
}

最后实现如下所示的空格:

photosRecycler.addItemDecoration(new SpacingItemDecoration(2,  dpToPx(this, 4), true));