RecyclerView GridLayoutManager: スパンの数を自動検出するには? 質問する

個人的には、このために RecyclerView をサブクラス化するのは好きではありません。なぜなら、スパン数を検出するのは GridLayoutManager の役割であるように思われるからです。そこで、RecyclerView と GridLayoutManager の Android ソース コードをいくつか調べた後、この目的を果たす GridLayoutManager を拡張した独自のクラスを作成しました。

public class GridAutofitLayoutManager extends GridLayoutManager
{
    private int columnWidth;
    private boolean isColumnWidthChanged = true;
    private int lastWidth;
    private int lastHeight;

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

    public GridAutofitLayoutManager(
        @NonNull final Context context,
        final int columnWidth,
        final int orientation,
        final boolean reverseLayout) {

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

    private int checkedColumnWidth(@NonNull final Context context, final 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(final int newColumnWidth) {
        if (newColumnWidth > 0 && newColumnWidth != columnWidth) {
            columnWidth = newColumnWidth;
            isColumnWidthChanged = true;
        }
    }

    @Override
    public void onLayoutChildren(@NonNull final RecyclerView.Recycler recycler, @NonNull final RecyclerView.State state) {
        final int width = getWidth();
        final int height = getHeight();
        if (columnWidth > 0 && width > 0 && height > 0 && (isColumnWidthChanged || lastWidth != width || lastHeight != height)) {
            final int totalSpace;
            if (getOrientation() == VERTICAL) {
                totalSpace = width - getPaddingRight() - getPaddingLeft();
            } else {
                totalSpace = height - getPaddingTop() - getPaddingBottom();
            }
            final int spanCount = Math.max(1, totalSpace / columnWidth);
            setSpanCount(spanCount);
            isColumnWidthChanged = false;
        }
        lastWidth = width;
        lastHeight = height;
        super.onLayoutChildren(recycler, state);
    }
}