A RecyclerView.ItemDecoration that can add spacing divider between items.

SpacingDividerItemDecoration.java

/**
 * SpacingDividerItemDecoration is a {@link RecyclerView.ItemDecoration} that can add space divider
 * between items of a {@link android.support.v7.widget.LinearLayoutManager}. It supports both {@link #HORIZONTAL}
 * and {@link #VERTICAL} orientations.
 */
public class SpacingDividerItemDecoration extends RecyclerView.ItemDecoration {

    @IntDef({HORIZONTAL, VERTICAL})
    @Retention(RetentionPolicy.SOURCE)
    public @interface OrientationMode {}
    public static final int HORIZONTAL = LinearLayout.HORIZONTAL;
    public static final int VERTICAL = LinearLayout.VERTICAL;

    @IntDef(flag = true, value = {SHOW_DIVIDER_NONE, SHOW_DIVIDER_BEGINNING, SHOW_DIVIDER_MIDDLE, SHOW_DIVIDER_END})
    @Retention(RetentionPolicy.SOURCE)
    public @interface DividerMode {}
    public static final int SHOW_DIVIDER_NONE = 0;
    public static final int SHOW_DIVIDER_BEGINNING = 1;
    public static final int SHOW_DIVIDER_MIDDLE = 1 << 1;
    public static final int SHOW_DIVIDER_END = 1 << 2;

    private int mSpacing;
    private int mShowDividers = SHOW_DIVIDER_MIDDLE;
    private int mOrientation = VERTICAL;

    public SpaceDividerItemDecoration(@OrientationMode int orientation) {
        setOrientation(orientation);
    }

    public void setSpace(@IntRange(from = 0) int spacing) {
        if (spacing < 0) {
            throw new IllegalArgumentException("Invalid spacing. It should be equal or large than zero");
        }
        mSpacing = spacing;
    }

    public void setOrientation(@OrientationMode int orientation) {
        if (orientation != HORIZONTAL && orientation != VERTICAL) {
            throw new IllegalArgumentException("Invalid orientation. It should be either HORIZONTAL or VERTICAL");
        }
        mOrientation = orientation;
    }

    public void setShowDividers(@DividerMode int showDividers) {
        if (showDividers == mShowDividers) {
            return;
        }
        mShowDividers = showDividers;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        outRect.set(0, 0, 0, 0);

        if (mShowDividers == SHOW_DIVIDER_NONE) {
            return;
        }

        int itemPosition = parent.getChildAdapterPosition(view);
        int itemCount = state.getItemCount();
        if (itemPosition == RecyclerView.NO_POSITION || itemCount < 1) {
            return;
        }

        if (itemPosition == 0 && (mShowDividers & SHOW_DIVIDER_BEGINNING) != 0) {
            addBeginningSpacing(outRect);
        }

        if (itemPosition == itemCount - 1 && (mShowDividers & SHOW_DIVIDER_END) != 0) {
            addEndSpacing(outRect);
        }

        if (itemCount > 1 && itemPosition != itemCount - 1 && (mShowDividers & SHOW_DIVIDER_MIDDLE) != 0) {
            addMiddleSpacing(outRect);
        }
    }

    /**
     * Add spacing at top or left base on orientation.
     *
     * @param outRect Rect to receive the output.
     */
    private void addBeginningSpacing(Rect outRect) {
        if (mOrientation == VERTICAL) {
            outRect.top = mSpacing;
        } else {
            outRect.left = mSpacing;
        }
    }

    /**
     * Add spacing at bottom or right base on orientation.
     *
     * @param outRect Rect to receive the output.
     */
    private void addMiddleSpacing(Rect outRect) {
        if (mOrientation == VERTICAL) {
            outRect.bottom = mSpacing;
        } else {
            outRect.right = mSpacing;
        }
    }

    /**
     * Add spacing at bottom or right base on orientation.
     *
     * @param outRect Rect to receive the output.
     */
    private void addEndSpacing(Rect outRect) {
        // The logic and implement are same with addMiddleSpace().
        addMiddleSpacing(outRect);
    }
}