问题在于这个代码块（链接到github中的源文件）
当我们在日历中选择两天时，这意味着我们正在选择日期范围的开始日期和结束日期。执行这个用于范围选择的代码块

} else if (adapter.getSelectedDates().size() == 2) {
    final List<CalendarDay> dates = adapter.getSelectedDates();
    if (dates.get(0).isAfter(dates.get(1))) {
        dispatchOnRangeSelected(dates.get(1), dates.get(0));
    } else {
        dispatchOnRangeSelected(dates.get(0), dates.get(1));
    }
}

当我们选择一个范围时，例如由2、3、4、5天组成的范围，那么所选天的列表的大小为4。当我们单击日期来取消选择范围时，在清除列表之前，这一天将从所选日期列表中删除，现在列表包含3个元素。结果这个代码块被执行，这意味着清除选定的范围

if (adapter.getSelectedDates().size() > 2) {
    adapter.clearSelections();
    adapter.setDateSelected(date, nowSelected);  //  re-set because adapter has been cleared
    dispatchOnDateSelected(date, nowSelected);

如果范围为4天及以上，一切正常。当范围由2天或3天组成时，则在“取消选择范围”上，所选日期的大小分别变为1或2（大小为-1，因为在所选范围中单击的日期在取消选择范围之前被删除），并且范围不会被清除，因为条件

if (adapter.getSelectedDates().size() > 2) {

未满足。要解决这个问题，您可以检查是否正在进行选择或取消选择，并执行正确的逻辑。我的快速解决方法是

case SELECTION_MODE_RANGE: {
        adapter.setDateSelected(date, nowSelected);
        if (adapter.getSelectedDates().size() > 2) {
            adapter.clearSelections();
            adapter.setDateSelected(date, nowSelected);  //  re-set because adapter has been cleared
            dispatchOnDateSelected(date, nowSelected);
        } else if (adapter.getSelectedDates().size() == 2) {
            final List<CalendarDay> dates = adapter.getSelectedDates();
            if (nowSelected) { // when selecting
                if (dates.get(0).isAfter(dates.get(1))) {
                    dispatchOnRangeSelected(dates.get(1), dates.get(0));
                } else {
                    dispatchOnRangeSelected(dates.get(0), dates.get(1));
                }
            } else { // in case range initially consisted of 3 dates, and now deselection happens
                adapter.clearSelections();
                adapter.setDateSelected(date, nowSelected);  //  re-set because adapter has been cleared
                dispatchOnDateSelected(date, nowSelected);
            }
        } else {
            if (nowSelected) {
                adapter.setDateSelected(date, nowSelected);
                dispatchOnDateSelected(date, nowSelected);
            } else { // in case range initially consisted of 2 dates, and now deselection happens
                adapter.clearSelections();
                adapter.setDateSelected(date, nowSelected);  //  re-set because adapter has been cleared
                dispatchOnDateSelected(date, nowSelected);
            }
        }
    }
    break;

我假设从调试器的输出来看，nowselected变量告诉我们是否正在进行选择或取消选择。