下面的代码工作得很好，每个列都有相同的宽度:

public class GridSpacingItemDecoration extends RecyclerView.ItemDecoration {

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

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

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

使用

1. 没有优势

int spanCount = 3; // 3 columns
int spacing = 50; // 50px
boolean includeEdge = false;
recyclerView.addItemDecoration(new GridSpacingItemDecoration(spanCount, spacing, includeEdge));

2. 与边缘

int spanCount = 3; // 3 columns
int spacing = 50; // 50px
boolean includeEdge = true;
recyclerView.addItemDecoration(new GridSpacingItemDecoration(spanCount, spacing, includeEdge));

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));

为了使https://stackoverflow.com/a/29905000/1649371(上面)解决方案工作，我必须修改以下方法(以及所有后续调用)

@SuppressWarnings("all")
protected int getItemSpanSize(RecyclerView parent, View view, int childIndex) {

    RecyclerView.LayoutManager mgr = parent.getLayoutManager();
    if (mgr instanceof GridLayoutManager) {
        return ((GridLayoutManager) mgr).getSpanSizeLookup().getSpanSize(childIndex);
    } else if (mgr instanceof StaggeredGridLayoutManager) {
        return ((StaggeredGridLayoutManager.LayoutParams) view.getLayoutParams()).isFullSpan() ? spanCount : 1;
    } else if (mgr instanceof LinearLayoutManager) {
        return 1;
    }

    return -1;
}

@SuppressWarnings("all")
protected int getItemSpanIndex(RecyclerView parent, View view, int childIndex) {

    RecyclerView.LayoutManager mgr = parent.getLayoutManager();
    if (mgr instanceof GridLayoutManager) {
        return ((GridLayoutManager) mgr).getSpanSizeLookup().getSpanIndex(childIndex, spanCount);
    } else if (mgr instanceof StaggeredGridLayoutManager) {
        return ((StaggeredGridLayoutManager.LayoutParams) view.getLayoutParams()).getSpanIndex();
    } else if (mgr instanceof LinearLayoutManager) {
        return 0;
    }

    return -1;
}

对我来说，完美的解决方案是设置RecyclerView的宽度它的layoutmanager为GridLayoutManager为wrap_content

这是我对SpacesItemDecoration的修改，它可以在顶部，底部，左边和右边同样采取numofcolumns和空间。

public class SpacesItemDecoration extends RecyclerView.ItemDecoration {
    private int space;
    private int mNumCol;

    public SpacesItemDecoration(int space, int numCol) {
        this.space = space;
        this.mNumCol=numCol;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view,
                               RecyclerView parent, RecyclerView.State state) {

        //outRect.right = space;
        outRect.bottom = space;
        //outRect.left = space;

        //Log.d("ttt", "item position" + parent.getChildLayoutPosition(view));
        int position=parent.getChildLayoutPosition(view);

        if(mNumCol<=2) {
            if (position == 0) {
                outRect.left = space;
                outRect.right = space / 2;
            } else {
                if ((position % mNumCol) != 0) {
                    outRect.left = space / 2;
                    outRect.right = space;
                } else {
                    outRect.left = space;
                    outRect.right = space / 2;
                }
            }
        }else{
            if (position == 0) {
                outRect.left = space;
                outRect.right = space / 2;
            } else {
                if ((position % mNumCol) == 0) {
                    outRect.left = space;
                    outRect.right = space/2;
                } else if((position % mNumCol) == (mNumCol-1)){
                    outRect.left = space/2;
                    outRect.right = space;
                }else{
                    outRect.left=space/2;
                    outRect.right=space/2;
                }
            }

        }

        if(position<mNumCol){
            outRect.top=space;
        }else{
            outRect.top=0;
        }
        // Add top margin only for the first item to avoid double space between items
        /*
        if (parent.getChildLayoutPosition(view) == 0 ) {

        } else {
            outRect.top = 0;
        }*/
    }
}

并在逻辑上使用下面的代码。

recyclerView.addItemDecoration(new SpacesItemDecoration(spacingInPixels, numCol));

如果你已经滚动到这个答案，我写了一个等间距库，支持垂直/水平，LTR/RTL，线性布局/GridLayout管理器和边缘包含。它基本上是一个文件，所以你可以复制粘贴该文件到你的代码中。

我试图支持StaggeredGridLayout，但这个布局返回的跨度索引不可靠。我很乐意听到任何有关这方面的建议。