flutter：如何在ListWheelChildLoopingListDelegate 中获取所选项目的索引？

Question

I have put a list of numbers(1-23) and a '-' in a ListWheelScrollView() to display time-selecting feature,(just in the following picture). I want add some feature in the item that is selected currently such as bold font, so my problem is how to get the selected item index ? My code is below.

new ListWheelScrollView.useDelegate(
                            itemExtent: 48,
                            physics: FixedExtentScrollPhysics(),
                            childDelegate: ListWheelChildLoopingListDelegate(
                              children: List<Widget>.generate(24, (index) {
                                if (index < 0 || index > 24) return null;
                                else if (index == 0) return Container(
                                  child: Text('-', style: CalendarTextStyle.timeStyle),
                                  alignment: Alignment.center,
                                );
                                else return Container(
                                  child: Text('${index}', style: CalendarTextStyle.timeStyle),
                                  alignment: Alignment.center,);
                              })
                            ),
                          ),

Answer 1

I have found a solution. use onSelectedItemChanged property in ListWheelScrollView.useDelegate , which can listen the item index when scolling.

ListWheelScrollView.useDelegate(
                        onSelectedItemChanged: (index) {setState(() {seletedItem = index;});}, // I initialized selectedItem = 0 in `initState()`
                        itemExtent: 48,
                        squeeze: 1,
                        controller: fsc,
                        physics: FixedExtentScrollPhysics(),
                        childDelegate: ListWheelChildLoopingListDelegate(
                          children: List<Widget>.generate(24, (index) {
                            if (index < 0 || index > 24) return null;
                            else if (index == 0) {
                              return Container(
                                child: Text('-', style:
                              seletedItem == index ?
                              CalendarTextStyle.selectedTimeStyle : CalendarTextStyle.timeStyle),
                              alignment: Alignment.center,);}
                            else {
                              return Container(
                                child: Text('$index', style:
                                seletedItem == index ?
                                CalendarTextStyle.selectedTimeStyle : CalendarTextStyle.timeStyle),
                                alignment: Alignment.center,);}
                          })
                        ),
                      ),

then we can got the effort like this: we can change the style of the selected item.