public void setSectionSelected(int sectionIndex, boolean selected) {
        SectionSelectionState state = getSectionSelectionState(sectionIndex);
        if (state.section != selected) {
            state.section = selected;

            // update all items and footers
            state.items.clear();
            for (int i = 0, n = getNumberOfItemsInSection(sectionIndex); i < n; i++) {
                state.items.put(i, selected);
            }

            if (doesSectionHaveFooter(sectionIndex)) {
                state.footer = selected;
            }

            notifySectionDataSetChanged(sectionIndex);
        }
    }
Set whether an entire section is selected. this affects ALL items (and footer) in section.

@param sectionIndex index of the section
@param selected     selection state
android/modules/module_common/src/main/java/github/tornaco/android/thanos/widget/section/SectioningAdapter.java