dart 下拉菜单在选项单击后不更新

5us2dqdw 于 2023-09-28 发布在其他

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我做了一个简单的类来存储我的下拉选项：

class ExperienceYearsRepository {
  List<String> returnExperienceYears() {
    return [
      "Menos de 1 ano",
      "Entre 1 e 3 anos",
      "Entre 3 e 5 anos",
      "Mais de 5 anos"
    ];
  }
}

下面有一个使用该列表的下拉实现，但是当单击任何选项时，下拉列表中显示的值始终是设置为experienceYears.first的值：

String experienceTime = "";
var experienceYearsRepository = ExperienceYearsRepository();
var experienceYears = [];

void initState() {
   experienceYears = experienceYearsRepository.returnExperienceYears();
   super.initState();
}

DropdownButton(
   isExpanded: true,
   value: experienceYears.first,
   items: experienceYears
       .map((experienceYear) => DropdownMenuItem(
             value: experienceYear,
             child: Text(experienceYear.toString()),
           ))
       .toList(),
   onChanged: (selectedExperienceTime) {
     setState(() {
        debugPrint(selectedExperienceTime as String?);
        experienceTime = selectedExperienceTime.toString();
     });
   }),

澄清一下，debugPrint实际上打印了正确的下拉列表项，所以问题在于显示它。有什么解决办法吗？我对Flutter很陌生，我很头疼，提前感谢！

dart

来源：https://stackoverflow.com/questions/77012264/dropdown-not-updating-after-option-click

2条答案

按热度按时间

2w2cym1i1#

String experienceTime = "";
var experienceYearsRepository = ExperienceYearsRepository();
var experienceYears = [];

void initState() {
experienceYears = experienceYearsRepository.returnExperienceYears();
  experienceTime = experienceYears.first; //assign here
super.initState();
}

DropdownButton(
 isExpanded: true,
 value: experienceTime, //use here
 items: experienceYears
   .map((experienceYear) => DropdownMenuItem(
         value: experienceYear,
         child: Text(experienceYear.toString()),
       ))
   .toList(),
  onChanged: (selectedExperienceTime) {
 setState(() {
    debugPrint(selectedExperienceTime as String?);
    experienceTime = selectedExperienceTime.toString();
 });
 }),

赞(0）回复(0）举报 2023-09-28

ecbunoof2#

DropdownButton（）的value属性不仅仅用于初始化，它是当前显示在菜单上的值。更改onChanged参数以更新它。你可以在init（）方法中指定它。

@override
void initState() {
    experienceYears = experienceYearsRepository.returnExperienceYears();
    experienceTime = experienceYears.first; //move initialization here
    super.initState();
}

   DropdownButton(
      isExpanded: true,
      value: experienceTime,   //controlling variable
      items: experienceYears
          .map((experienceYear) => DropdownMenuItem(
                value: experienceYear,
                child: Text(experienceYear.toString()),
              ))
          .toList(),
      onChanged: (selectedExperienceTime) {
        setState(
          () {
            debugPrint(selectedExperienceTime as String?);
            experienceTime = selectedExperienceTime.toString(); //update it here
          },
        );
      },
    ),

赞(0）回复(0）举报 2023-09-28

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dart 下拉菜单在选项单击后不更新

2条答案

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