可以使用FlexboxLayoutManager和FlexboxItemDecoration来实现固定列数的布局。

在XML布局中定义使用FlexboxLayout，并设置布局属性：

然后在代码中，使用FlexboxLayoutManager设置固定列数：

FlexboxLayoutManager layoutManager = new FlexboxLayoutManager(context);
layoutManager.setFlexDirection(FlexDirection.ROW);
layoutManager.setFlexWrap(FlexWrap.WRAP);
layoutManager.setAlignItems(AlignItems.STRETCH);
layoutManager.setJustifyContent(JustifyContent.SPACE_BETWEEN);
layoutManager.setFlexItemCount(numColumns);  //设置列数

RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
recyclerView.setLayoutManager(layoutManager);

使用FlexboxItemDecoration设置间隔：

FlexboxItemDecoration itemDecoration = new FlexboxItemDecoration(context);
itemDecoration.setFlexDirection(FlexDirection.ROW);
itemDecoration.setJustifyContent(JustifyContent.SPACE_BETWEEN);
itemDecoration.setWithOffset(true);
itemDecoration.setHorizontalOffset(10);  //设置水平方向间隔
itemDecoration.setVerticalOffset(10);  //设置垂直方向间隔

RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
recyclerView.addItemDecoration(itemDecoration);