Equally spacing recyclerView items with the provided space.

SpacingItemDecoration.java

public class SpacingItemDecoration extends RecyclerView.ItemDecoration {

    private static final String TAG = "SPACE";

    private int spacing;

    public SpacingItemDecoration(int spacing) {
        this.spacing = spacing;
    }

    @Override
    public void getItemOffsets(@NotNull Rect layout, @NotNull View view, RecyclerView parent, @NotNull RecyclerView.State state) {
        RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
        RecyclerView.Adapter adapter = parent.getAdapter();
        int position = parent.getChildAdapterPosition(view);
        if (layoutManager instanceof GridLayoutManager) {
            GridLayoutManager manager = (GridLayoutManager) parent.getLayoutManager();
            if (manager != null && adapter != null) {
                int spanCount = manager.getSpanCount();
                if (spanCount >= 2) {
                    int numOfRows = adapter.getItemCount() / spanCount;
                    int numOfColumns = spanCount;

                    int row = (position / spanCount) + 1;
                    int column = (position % spanCount) + 1;

                    if (column == 1) {
                        layout.left = spacing;
                        layout.right = spacing / 2;
                    } else if (column == numOfColumns) {
                        layout.left = spacing / 2;
                        layout.right = spacing;
                    } else {
                        layout.left = spacing / 2;
                        layout.right = spacing / 2;
                    }

                    if (row == 1) {
                        layout.top = spacing;
                        layout.bottom = spacing / 2;
                    } else if (row == numOfRows) {
                        layout.top = spacing / 2;
                        layout.bottom = spacing;
                    } else {
                        layout.top = spacing / 2;
                        layout.bottom = spacing / 2;
                    }
                } else {
                    //GridLayoutManager with 1 span
                    int numOfItems = adapter.getItemCount();
                    int row = position + 1;
                    if (row == 1) {
                        layout.top = spacing;
                        layout.left = spacing;
                        layout.right = spacing;
                        layout.bottom = spacing / 2;
                    } else if (row == numOfItems) {
                        layout.top = spacing / 2;
                        layout.left = spacing;
                        layout.right = spacing;
                        layout.bottom = spacing;
                    } else {
                        layout.top = spacing / 2;
                        layout.left = spacing;
                        layout.right = spacing;
                        layout.bottom = spacing / 2;
                    }
                }
            }
        } else if (layoutManager instanceof LinearLayoutManager) {
            //Supporting LinearLayoutManager with Horizontal and Vertical Orientation
            LinearLayoutManager manager = (LinearLayoutManager) parent.getLayoutManager();
            if (manager != null && adapter != null) {
                if (manager.getOrientation() == LinearLayoutManager.HORIZONTAL) {
                    int numOfItems = adapter.getItemCount();
                    int column = position + 1;
                    if (column == 1) {
                        layout.top = spacing;
                        layout.left = spacing;
                        layout.right = spacing / 2;
                        layout.bottom = spacing;
                    } else if (column == numOfItems) {
                        layout.top = spacing;
                        layout.left = spacing / 2;
                        layout.right = spacing;
                        layout.bottom = spacing;
                    } else {
                        layout.top = spacing;
                        layout.left = spacing / 2;
                        layout.right = spacing / 2;
                        layout.bottom = spacing;
                    }
                } else {
                    int numOfItems = adapter.getItemCount();
                    int row = position + 1;
                    if (row == 1) {
                        layout.top = spacing;
                        layout.left = spacing;
                        layout.right = spacing;
                        layout.bottom = spacing / 2;
                    } else if (row == numOfItems) {
                        layout.top = spacing / 2;
                        layout.left = spacing;
                        layout.right = spacing;
                        layout.bottom = spacing;
                    } else {
                        layout.top = spacing / 2;
                        layout.left = spacing;
                        layout.right = spacing;
                        layout.bottom = spacing / 2;
                    }
                }
            }
        }
    }
}