下面是一个不需要“spanCount”(列数)的解决方案 我使用它是因为我使用GridAutofitLayoutManager(根据所需的单元格大小计算列数)

(注意，这将只工作在GridLayoutManager)

public class GridSpacesItemDecoration extends RecyclerView.ItemDecoration {
    private final boolean includeEdge;
    private int spacing;


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

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        if (parent.getLayoutManager() instanceof GridLayoutManager) {
            GridLayoutManager layoutManager = (GridLayoutManager)parent.getLayoutManager();
            int spanCount = layoutManager.getSpanCount();
            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
                }
            }

        }

    }
}

这是GridAutofitLayoutManager是谁感兴趣:

public class GridAutofitLayoutManager extends GridLayoutManager {
    private int mColumnWidth;
    private boolean mColumnWidthChanged = true;

    public GridAutofitLayoutManager(Context context, int columnWidth)
    {
        /* Initially set spanCount to 1, will be changed automatically later. */
        super(context, 1);
        setColumnWidth(checkedColumnWidth(context, columnWidth));
    }

    public GridAutofitLayoutManager(Context context,int unit, int columnWidth)
    {
        /* Initially set spanCount to 1, will be changed automatically later. */
        super(context, 1);
        int pixColumnWidth = (int) TypedValue.applyDimension(unit, columnWidth, context.getResources().getDisplayMetrics());
        setColumnWidth(checkedColumnWidth(context, pixColumnWidth));
    }

    public GridAutofitLayoutManager(Context context, int columnWidth, int orientation, boolean reverseLayout)
    {
        /* Initially set spanCount to 1, will be changed automatically later. */
        super(context, 1, orientation, reverseLayout);
        setColumnWidth(checkedColumnWidth(context, columnWidth));
    }

    private int checkedColumnWidth(Context context, int columnWidth)
    {
        if (columnWidth <= 0)
        {
            /* Set default columnWidth value (48dp here). It is better to move this constant
            to static constant on top, but we need context to convert it to dp, so can't really
            do so. */
            columnWidth = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 48,
                    context.getResources().getDisplayMetrics());
        }
        return columnWidth;
    }

    public void setColumnWidth(int newColumnWidth)
    {
        if (newColumnWidth > 0 && newColumnWidth != mColumnWidth)
        {
            mColumnWidth = newColumnWidth;
            mColumnWidthChanged = true;
        }
    }

    @Override
    public void onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state)
    {
        int width = getWidth();
        int height = getHeight();
        if (mColumnWidthChanged && mColumnWidth > 0 && width > 0 && height > 0)
        {
            int totalSpace;
            if (getOrientation() == VERTICAL)
            {
                totalSpace = width - getPaddingRight() - getPaddingLeft();
            }
            else
            {
                totalSpace = height - getPaddingTop() - getPaddingBottom();
            }
            int spanCount = Math.max(1, totalSpace / mColumnWidth);
            setSpanCount(spanCount);

            mColumnWidthChanged = false;
        }
        super.onLayoutChildren(recycler, state);
    }
}

最后:

mDevicePhotosView.setLayoutManager(new GridAutofitLayoutManager(getContext(), getResources().getDimensionPixelSize(R.dimen.item_size)));
mDevicePhotosView.addItemDecoration(new GridSpacesItemDecoration(Util.dpToPx(getContext(), 2),true));

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));

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。

对于任何像我一样，想要最好的答案，但在kotlin，这里是:

class GridItemDecoration(
    val spacing: Int,
    private val spanCount: Int,
    private val includeEdge: Boolean
) :
    RecyclerView.ItemDecoration() {

    /**
     * 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
    ) {
        val position = parent.getChildAdapterPosition(view) // item position
        val 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
            }
        }
    }
}

如果你想从dimensions .xml中获取数字，然后将其转换为原始像素，你可以使用getDimensionPixelOffset简单地做到这一点，就像这样:

recyclerView.addItemDecoration(
                GridItemDecoration(
                    resources.getDimensionPixelOffset(R.dimen.h1),
                    3,
                    true
                )
            )

下面的代码将处理StaggeredGridLayoutManager、GridLayoutManager和LinearLayoutManager。

public class SpacesItemDecoration extends RecyclerView.ItemDecoration {

    private int halfSpace;

    public SpacesItemDecoration(int space) {
        this.halfSpace = space / 2;
    }

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

        if (parent.getPaddingLeft() != halfSpace) {
            parent.setPadding(halfSpace, halfSpace, halfSpace, halfSpace);
            parent.setClipToPadding(false);
        }

        outRect.top = halfSpace;
        outRect.bottom = halfSpace;
        outRect.left = halfSpace;
        outRect.right = halfSpace;
    }
}

然后使用它

mRecyclerView.addItemDecoration(new SpacesItemDecoration(mMargin));

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;
        }
    }
    }
}