適用於GridLayoutManager橫豎間隔均可設定；

用法：

rv.addItemDecoration(new DividerGridItemDecoration(Color.TRANSPARENT, 30, 30, Color.TRANSPARENT, 0));

DividerGridItemDecoration類：

public class DividerGridItemDecoration extends RecyclerView.ItemDecoration {

    private Drawable mDivider;
    private int mDividerHSpacing;
 
    private int mDividerVSpacing;
    private Drawable mLastDivider;
    private int mLastDividerSize;
    public DividerGridItemDecoration() {
        set(new ColorDrawable(Color.TRANSPARENT), mDividerHSpacing, mDividerVSpacing, new ColorDrawable(Color.TRANSPARENT), mLastDividerSize);
}

    public 
 
DividerGridItemDecoration(int horizaontalSpacing, int verticalSpacing, int lastDividerSize) {
        set(new ColorDrawable(Color.TRANSPARENT), horizaontalSpacing, verticalSpacing, new ColorDrawable(Color.TRANSPARENT), lastDividerSize);
}

    public DividerGridItemDecoration(Drawable divider, int horizaontalSpacing, int 
 
verticalSpacing, Drawable lastDivider, int lastDividerSize) {
        set(divider, horizaontalSpacing, verticalSpacing, lastDivider, lastDividerSize);
}

    public DividerGridItemDecoration(@ColorInt int dividerColor, int horizaontalSpacing, int verticalSpacing, @ColorInt int lastDividerColor, int lastDividerSize) {
        set(new ColorDrawable(dividerColor), horizaontalSpacing, verticalSpacing, new ColorDrawable(lastDividerColor), lastDividerSize);
}

    /**
     * @param divider
* @param horizaontalSpacing 橫向間距
     * @param verticalSpacing    縱向間距
     * @param lastDivider
* @param lastDividerSize    最後一行的後邊距離，大於0才會生效
     */
private void set(Drawable divider, int horizaontalSpacing, int verticalSpacing, Drawable lastDivider, int lastDividerSize) {
        this.mDivider = divider;
        this.mDividerHSpacing = horizaontalSpacing;
        this.mDividerVSpacing = verticalSpacing;
        this.mLastDivider = lastDivider;
        this.mLastDividerSize = lastDividerSize;
}

    @Override
public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
        super.onDraw(c, parent, state);
        if (mDivider == null) {
            return;
}
        if (mDividerHSpacing > 0) {
            drawHorizontalSpacing(c, parent);
}
        if (mDividerVSpacing > 0) {
            drawVerticalSpacing(c, parent);
}
        if (mLastDividerSize > 0) {
            drawLastSpacing(c, parent);
}
    }

    /**
     * 繪製橫向間距,不包括最後一列
     *
     * @param c
* @param parent
*/
private void drawHorizontalSpacing(Canvas c, RecyclerView parent) {
        int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            final View child = parent.getChildAt(i);
// 前邊不用考慮是否是最後一列
if (i < childCount - ((GridLayoutManager) parent.getLayoutManager()).getSpanCount()
                    || (parent.getLayoutManager().canScrollVertically() || !isLastGridRaw(parent, child))) {
                drawHorizontal(c, child, mDivider, mDividerHSpacing);
}
        }
    }

    private void drawHorizontal(Canvas c, View child, Drawable divider, int spacing) {
        final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
        final int left = child.getRight() + params.rightMargin;
        final int right = left + spacing;
        final int top = child.getTop() - params.topMargin;
        final int bottom = child.getBottom() + params.bottomMargin;
divider.setBounds(left, top, right, bottom);
divider.draw(c);
}

    /**
     * 繪製縱向間距，不包括最後一行
     *
     * @param c
* @param parent
*/
private void drawVerticalSpacing(Canvas c, RecyclerView parent) {
        int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            final View child = parent.getChildAt(i);
// 前邊不用考慮是否是最後一行
if (i < childCount - ((GridLayoutManager) parent.getLayoutManager()).getSpanCount()
                    || (parent.getLayoutManager().canScrollHorizontally() || !isLastGridRaw(parent, child))) {
                drawVertical(c, child, mDivider, mDividerVSpacing);
}
        }
    }

    private void drawVertical(Canvas c, View child, Drawable divider, int spacing) {
        final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
        final int left = child.getLeft() - params.leftMargin;
        final int right = child.getRight() + params.rightMargin;
        final int top = child.getBottom() + params.bottomMargin;
        final int bottom = top + spacing;
divider.setBounds(left, top, right, bottom);
divider.draw(c);
}

    /**
     * 繪製最後
     *
     * @param c
* @param parent
*/
private void drawLastSpacing(Canvas c, RecyclerView parent) {
        int childCount = parent.getChildCount();
        int i = childCount - ((GridLayoutManager) parent.getLayoutManager()).getSpanCount();
        for (; i < childCount; i++) {
            final View child = parent.getChildAt(i);
            if (isLastGridRaw(parent, child)) {
                if (parent.getLayoutManager().canScrollHorizontally()) {
                    drawHorizontal(c, child, mLastDivider, mLastDividerSize);
} else if (parent.getLayoutManager().canScrollVertically()) {
                    drawVertical(c, child, mLastDivider, mLastDividerSize);
}
            }
        }

    }

    @Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        super.getItemOffsets(outRect, view, parent, state);
GridLayoutManager gridLayoutManager = (GridLayoutManager) parent.getLayoutManager();
        if (gridLayoutManager.canScrollHorizontally()) {
            if (isLastGridRaw(parent, view)) {// 如果是最後一列
if (parent.getChildAdapterPosition(view) == gridLayoutManager.getItemCount() - 1) {// 最後一個
outRect.set(0, 0, mLastDividerSize, 0);
} else {
                    outRect.set(0, 0, mLastDividerSize, mDividerVSpacing);
}
            } /*
                 * else if (RecyclerViewUtil.isLastGridColum(parent, view)) {//
             * 如果是最後一行，則不需要繪製底部 outRect.set(0, 0, mDividerHSpacing, 0); }
             */ else {
                outRect.set(0, 0, mDividerHSpacing, mDividerVSpacing);
}
        } else if (gridLayoutManager.canScrollVertically()) {
            if (isLastGridRaw(parent, view)) {// 如果是最後一行，則不需要繪製底部
if (parent.getChildAdapterPosition(view) == gridLayoutManager.getItemCount() - 1) {
                    outRect.set(0, 0, 0, mLastDividerSize);
} else {
                    outRect.set(0, 0, mDividerHSpacing, mLastDividerSize);
}
            } /*
                 * else if (RecyclerViewUtil.isLastGridColum(parent, view)) {//
             * 如果是最後一列，則不需要繪製右邊 outRect.set(0, 0, 0, mDividerVSpacing); }
             */ else {
                outRect.set(0, 0, mDividerHSpacing, mDividerVSpacing);
}
        }

    }

    /**
     * 是否是最後一行，相對於recyclerView的方向而言,橫向表示最右邊，豎向表示最下邊
     *
     * @param parent
* @param view
* @return
*/
public boolean isLastGridRaw(RecyclerView parent, View view) {
        RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
        if (layoutManager instanceof GridLayoutManager) {
            GridLayoutManager gridLayoutManager = (GridLayoutManager) layoutManager;
GridLayoutManager.SpanSizeLookup spanSizeLookUp = gridLayoutManager.getSpanSizeLookup();
            int childPosition = parent.getChildAdapterPosition(view);
            int itemCount = gridLayoutManager.getItemCount();
            int spanCountTotal = 0;
            int spanCountChild = 0;
            if (childPosition >= itemCount - gridLayoutManager.getSpanCount()) {
                for (int i = 0; i < itemCount; i++) {
                    spanCountTotal += spanSizeLookUp.getSpanSize(i);
                    if (i <= childPosition) {
                        spanCountChild += spanSizeLookUp.getSpanSize(i);
}
                }
                int lastRowCount = spanCountTotal % gridLayoutManager.getSpanCount();
                if (lastRowCount == 0) {
                    lastRowCount = gridLayoutManager.getSpanCount();
}
                if (spanCountChild > spanCountTotal - lastRowCount) {
                    return true;
}
            }

        } else if (layoutManager instanceof StaggeredGridLayoutManager) {
            // TODO: 17/1/16
}
        return false;
}
}