RecyclerView的ItemDecoration

根据设置的不同LayoutManager，设置不同的距离

public class SpaceItemDecoration extends RecyclerView.ItemDecoration {

    public static final int ORIENTATION_HORIZONTAL = 0;
    public static final int ORIENTATION_VERTICAL = 1;
    public static final int ORIENTATION_GRID = 2;

    private int orientation;
    private int leftSpace;
    private int topSpace;
    private int column;

    public static SpaceItemDecoration newHorizontalDecoration(int space) {
        return new SpaceItemDecoration(ORIENTATION_HORIZONTAL, space, 0, 0);
    }

    public static SpaceItemDecoration newVerticalDecoration(int space) {
        return new SpaceItemDecoration(ORIENTATION_VERTICAL, 0, space, 0);
    }

    public static SpaceItemDecoration newGridDecoration(int column, int leftSpace, int topSpace) {
        return new SpaceItemDecoration(ORIENTATION_GRID, leftSpace, topSpace, column);
    }

    public SpaceItemDecoration(int orientation, int leftSpace, int topSpace, int column) {
        this.orientation = orientation;
        this.leftSpace = leftSpace;
        this.topSpace = topSpace;
        this.column = column;
    }

    @Override
    public void getItemOffsets(@NonNull Rect outRect, @NonNull View view, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {
        outRect.left = leftSpace;
        outRect.top = topSpace;
        switch (orientation) {
            case ORIENTATION_HORIZONTAL:
            // 水平的LayoutManager，设置第一个item与左边界紧挨
                if (parent.getChildAdapterPosition(view) == 0) {
                    outRect.left = 0;
                }
                break;
            case ORIENTATION_VERTICAL:
            // 垂直的LayoutManager，设置第一个item与上边界紧挨
                if (parent.getChildAdapterPosition(view) == 0) {
                    outRect.top = 0;
                }
                break;
            case ORIENTATION_GRID:
            // 网格布局的LayoutManager，设置每一行的第一个item与左边界        
            //紧挨，每一行最后一个item与右边界紧挨，其余自动向右侧偏移
                int mod = parent.getChildAdapterPosition(view) % column;
                outRect.left = leftSpace * mod;
                break;
        }
    }

}

调用：

// 水平/垂直布局
LinearLayoutManager manager = new LinearLayoutManager(mBaseActivity);
        manager.setOrientation(RecyclerView.HORIZONTAL);

recyclerView.addItemDecoration(SpaceItemDecoration.newHorizontalDecoration(
                DimensionUtil.dp2px(this, DimensionUtil.DEFAULT_RECYCLER_VIEW_ITEM_SPACE)));

// 网格布局
// 获取屏幕宽度，减去padding/margin等等，得到recyclerView的实际宽度
// 这里如果直接使用recyclerView.getWidth()可能为0，需要注意
// 然后均分成 column * (column - 1) 份，用于偏移
GridLayoutManager manager = new GridLayoutManager(this, COLUMN_COUNT);

DisplayMetrics metrics = new DisplayMetrics();
activity.getWindowManager().getDefaultDisplay().getMetrics(metrics);
final int viewWidth = (int) (metrics.widthPixels * 0.96);
final int itemWidth = activity.getResources().getDimensionPixelOffset(R.dimen.movie_recycler_view_width);
final int leftSpace = (viewWidth - column * itemWidth) / ((column * (column - 1)));
final int topSpace = DimensionUtil.dp2px(activity, DimensionUtil.DEFAULT_RECYCLER_VIEW_ITEM_SPACE);   
recyclerView.addItemDecoration(SpaceItemDecoration.newGridDecoration(column, leftSpace, topSpace));