Contextual Action Bar with Android's ExpandableListView

I have put together a sample project on Github illustrating that the Contextual Action Bar pattern can be applied to Android's ExpandableListView, if your use case implies that you either want to select groups or the childs and do not need a mixed selection.

The magic is quite simple, it mainly consists in storing the type of selection in the ActionMode.Callback's onItemCheckedStateChanged() method:

    @Override
    public void onItemCheckedStateChanged(ActionMode mode, int position,
                                          long id, boolean checked) {
      int count = lv.getCheckedItemCount();
      if (count == 1) {
        expandableListSelectionType = ExpandableListView.getPackedPositionType(
            lv.getExpandableListPosition(position));
      }
      mode.setTitle(String.valueOf(count));
      configureMenu(mode.getMenu(), count);
    }

Then you need to implement onChildClick() and onGroupClick() listeners that check the list items once action mode is active:

    @Override
    public boolean onGroupClick(ExpandableListView parent, View v, int groupPosition, long id) {
      if (mActionMode != null)  {
        if (expandableListSelectionType == ExpandableListView.PACKED_POSITION_TYPE_GROUP) {
          int flatPosition = parent.getFlatListPosition(ExpandableListView.getPackedPositionForGroup(groupPosition));
          parent.setItemChecked(
              flatPosition,
              !parent.isItemChecked(flatPosition));
          return true;
        }
      }
      return false;
    }
    @Override
    public boolean onChildClick(ExpandableListView parent, View v,
        int groupPosition, int childPosition, long id) {
      if (mActionMode != null)  {
        if (expandableListSelectionType == ExpandableListView.PACKED_POSITION_TYPE_CHILD) {
          int flatPosition = parent.getFlatListPosition(
              ExpandableListView.getPackedPositionForChild(groupPosition,childPosition));
          parent.setItemChecked(
              flatPosition,
              !parent.isItemChecked(flatPosition));
        }
        return true;
      }
      return false;
    }

The sample project also illustrates a technique of defining the context actions as part of four groups, depending on two combined criteria:

• actions for groups or children
• bulk actions that can be applied to multiple items, and single item actions