Is there any way to show the unique value in Dropdownbutton list? - flutter

Question

My code is :
Column(
mainAxisAlignment: MainAxisAlignment.start,
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Text.rich(
TextSpan(
children: [
TextSpan(
text: 'Select District',
style: getSemiBoldStyle(
color: Colormanager.lightGrey,
fontSize: AppSize.s14),
),
TextSpan(
text: AppStrings.star,
style: getSemiBoldStyle(
color: Colormanager.red,
fontSize: AppSize.s14),
),
],
),
),
const SizedBox(
height: AppSize.s4,
),
DropdownSearch<CoverageArea>(
popupProps: PopupProps.menu(
showSearchBox: true,
// disabledItemFn: (String s) => s.startsWith('I'),
searchFieldProps: TextFieldProps(
style: getBoldStyle(
color: Colormanager.black,
fontSize: FontSize.s15),
),
itemBuilder: (context, item, isSelected) =>
isSelected
? Padding(
padding: const EdgeInsets.all(8.0),
child: Text(
item.district!,
style: getBoldStyle(
color: Colormanager.primary),
),
)
: Container(
padding: const EdgeInsets.all(8.0),
margin: const EdgeInsets.only(
bottom: 4),
color: Colormanager.lightGrey
.withOpacity(0.2),
child: Text(
item.district!,
style: getBoldStyle(
color: Colormanager.black,
fontSize: FontSize.s15),
),
),
),
items: controller.coverageAreas,
dropdownDecoratorProps: DropDownDecoratorProps(
baseStyle:
getSemiBoldStyle(color: Colormanager.black),
dropdownSearchDecoration: const InputDecoration(
// labelText: "Menu mode",
// hintText: "country in menu mode",
),
),
onChanged: (value) {
controller.selectedDistrict = value;
controller.selectDistrict.value =
value!.district.toString();
},
itemAsString: (item) => item.district.toString(),
// selectedItem: controller.selectArea.value,
),
],
),
and the api call show me :
{
"Status": true,
"message": "Coverage Area List",
"data": [
{
"id": 898,
"inside": 0,
"zone_name": "OSD Operation",
"district": "Barguna",
"area": "Barguna Sadar",
"district_id": 35,
"zone_id": 14,
"post_code": null,
"h_delivery": null,
"oneRe": null,
"oneUr": null,
"plusRe": null,
"plusUr": null,
"cod": null,
"insurance": null,
"status": 0,
"created_at": "2023-01-17 15:40:08",
"updated_at": "2023-01-17 15:40:08"
},
{
"id": 897,
"inside": 0,
"zone_name": "OSD Operation",
"district": "Barguna",
"area": "Taltoly",
"district_id": 35,
"zone_id": 14,
"post_code": null,
"h_delivery": null,
"oneRe": null,
"oneUr": null,
"plusRe": null,
"plusUr": null,
"cod": null,
"insurance": null,
"status": 0,
"created_at": "2023-01-17 15:39:49",
"updated_at": "2023-01-17 15:39:49"
},
{
"id": 896,
"inside": 0,
"zone_name": "OSD Operation",
"district": "Barguna",
"area": "Amtoly",
"district_id": 35,
"zone_id": 14,
"post_code": null,
"h_delivery": null,
"oneRe": null,
"oneUr": null,
"plusRe": null,
"plusUr": null,
"cod": null,
"insurance": null,
"status": 0,
"created_at": "2023-01-17 15:39:29",
"updated_at": "2023-01-17 15:39:29"
},
{
"id": 895,
"inside": 0,
"zone_name": "OSD Operation",
"district": "Barguna",
"area": "Betage",
"district_id": 35,
"zone_id": 14,
"post_code": null,
"h_delivery": null,
"oneRe": null,
"oneUr": null,
"plusRe": null,
"plusUr": null,
"cod": null,
"insurance": null,
"status": 0,
"created_at": "2023-01-17 15:39:05",
"updated_at": "2023-01-17 15:39:05"
},
{
"id": 891,
"inside": 0,
"zone_name": "OSD Operation",
"district": "Barishal",
"area": "Barisal Bandor Thana",
"district_id": 33,
"zone_id": 14,
"post_code": null,
"h_delivery": null,
"oneRe": null,
"oneUr": null,
"plusRe": null,
"plusUr": null,
"cod": null,
"insurance": null,
"status": 0,
"created_at": "2023-01-17 15:35:28",
"updated_at": "2023-01-17 15:35:28"
},
so on..............
I want to show Barguna district just once and area in dependable dropdownbutton in next. but how can i do it???
This is the output
how can i just show one name just once???

Answer 1

While there are multiple items contains single value, I will suggest you to use String dataType instead of CoverageArea. then you can create a set of string from data.
So the item will be like
final List<String> items = controller.coverageAreas.map((e)=> e.district.trim()).toSet().toList();
now use this items on dropdown. and the value will be return as String DropdownSearch<String>(