I have listview that contain this dropdown. Items of the drop are shown, it’s from API, but it throw some error when i select the value
Either zero or 2 or more [DropdownMenuItem]s were detected with the same value
‘package:flutter/src/material/dropdown.dart’:
Failed assertion: line 888 pos 15: ‘items == null || items.isEmpty || value == null ||
items.where((DropdownMenuItem item) {
return item.value == value;
}).length == 1′”
I guess it’s throw that error because of duplicate dropdown in the lisview that use same item.I think it’s should use index for different the dropdown. Any suggestions code examples please!
<code>List? answerList;
</code>
<code>List? answerList;
</code>
List? answerList;
This is function to fetch data:
<code>void answerSetupDropdown() async {
var headers = {
'Accept': 'application/json',
'Content-Type': 'application/json',
};
var request =
http.Request('POST', Uri.parse(baseLaravelAPI + '/api/start_section'));
request.body = json.encode({
"staffid": widget.staffId.toString(),
"form_open_id": widget.formOpenId.toString(),
"section_id": widget.sectionId.toString(),
"form_id": widget.formId.toString(),
"confirm_no": widget.confNo.toString()
});
request.headers.addAll(headers);
http.StreamedResponse response = await request.send();
if (response.statusCode == 200) {
final res = jsonDecode(await response.stream.bytesToString());
answerList = res["data"]["answer_list"];
loading = false;
} else {
throw Exception('Unable to fetch products from the REST API');
}
}
</code>
<code>void answerSetupDropdown() async {
var headers = {
'Accept': 'application/json',
'Content-Type': 'application/json',
};
var request =
http.Request('POST', Uri.parse(baseLaravelAPI + '/api/start_section'));
request.body = json.encode({
"staffid": widget.staffId.toString(),
"form_open_id": widget.formOpenId.toString(),
"section_id": widget.sectionId.toString(),
"form_id": widget.formId.toString(),
"confirm_no": widget.confNo.toString()
});
request.headers.addAll(headers);
http.StreamedResponse response = await request.send();
if (response.statusCode == 200) {
final res = jsonDecode(await response.stream.bytesToString());
answerList = res["data"]["answer_list"];
loading = false;
} else {
throw Exception('Unable to fetch products from the REST API');
}
}
</code>
void answerSetupDropdown() async {
var headers = {
'Accept': 'application/json',
'Content-Type': 'application/json',
};
var request =
http.Request('POST', Uri.parse(baseLaravelAPI + '/api/start_section'));
request.body = json.encode({
"staffid": widget.staffId.toString(),
"form_open_id": widget.formOpenId.toString(),
"section_id": widget.sectionId.toString(),
"form_id": widget.formId.toString(),
"confirm_no": widget.confNo.toString()
});
request.headers.addAll(headers);
http.StreamedResponse response = await request.send();
if (response.statusCode == 200) {
final res = jsonDecode(await response.stream.bytesToString());
answerList = res["data"]["answer_list"];
loading = false;
} else {
throw Exception('Unable to fetch products from the REST API');
}
}
This is dropdown that show the item:
<code> ListView.builder(
itemCount: chilList!.length,
itemBuilder: (context, i) {
loading == false
? Expanded(
// alignment: Alignment.centerLeft,
child: Theme(
data: Theme.of(context).copyWith(
unselectedWidgetColor: lightblue,
),
child: DropdownButton<dynamic>(
underline: SizedBox(),
hint: Text("Select Answer"),
value: selectedValue,
onChanged: (dynamic value) {
setState(() {
selectedValue =
(value["answer_name"])
.toString();
});
// selectedValue =
// (valueSel["answer_name"])
// .toString();
},
items: answerList!.map((answer) {
return DropdownMenuItem<dynamic>(
value: answer,
child: Row(
children: <Widget>[
SizedBox(
width: 10,
),
Text(
answer["answer_name"]
.toString(),
style: TextStyle(
color: Color(
int.parse((answer[
"answer_color"])
.replaceAll(
RegExp(
'#'),
'0xFF')))),
),
],
),
);
}).toList(),
),
),
)
: CircularProgressIndicator(),
});
</code>
<code> ListView.builder(
itemCount: chilList!.length,
itemBuilder: (context, i) {
loading == false
? Expanded(
// alignment: Alignment.centerLeft,
child: Theme(
data: Theme.of(context).copyWith(
unselectedWidgetColor: lightblue,
),
child: DropdownButton<dynamic>(
underline: SizedBox(),
hint: Text("Select Answer"),
value: selectedValue,
onChanged: (dynamic value) {
setState(() {
selectedValue =
(value["answer_name"])
.toString();
});
// selectedValue =
// (valueSel["answer_name"])
// .toString();
},
items: answerList!.map((answer) {
return DropdownMenuItem<dynamic>(
value: answer,
child: Row(
children: <Widget>[
SizedBox(
width: 10,
),
Text(
answer["answer_name"]
.toString(),
style: TextStyle(
color: Color(
int.parse((answer[
"answer_color"])
.replaceAll(
RegExp(
'#'),
'0xFF')))),
),
],
),
);
}).toList(),
),
),
)
: CircularProgressIndicator(),
});
</code>
ListView.builder(
itemCount: chilList!.length,
itemBuilder: (context, i) {
loading == false
? Expanded(
// alignment: Alignment.centerLeft,
child: Theme(
data: Theme.of(context).copyWith(
unselectedWidgetColor: lightblue,
),
child: DropdownButton<dynamic>(
underline: SizedBox(),
hint: Text("Select Answer"),
value: selectedValue,
onChanged: (dynamic value) {
setState(() {
selectedValue =
(value["answer_name"])
.toString();
});
// selectedValue =
// (valueSel["answer_name"])
// .toString();
},
items: answerList!.map((answer) {
return DropdownMenuItem<dynamic>(
value: answer,
child: Row(
children: <Widget>[
SizedBox(
width: 10,
),
Text(
answer["answer_name"]
.toString(),
style: TextStyle(
color: Color(
int.parse((answer[
"answer_color"])
.replaceAll(
RegExp(
'#'),
'0xFF')))),
),
],
),
);
}).toList(),
),
),
)
: CircularProgressIndicator(),
});
Ensure that the selectedValue is unique for each item
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That means your answerList variable has 2 identical values. Because DropdownMenuItem value must be unique.
In example:
Bad
<code>List answerList = [1,2,3,3];
</code>
<code>List answerList = [1,2,3,3];
</code>
List answerList = [1,2,3,3];
It’s bad because answer has two
3(not unique), it will confusingDropdownButton
Good
<code>List answerList = [1, 3, 5, 6, 8, 9];
</code>
<code>List answerList = [1, 3, 5, 6, 8, 9];
</code>
List answerList = [1, 3, 5, 6, 8, 9];
It’s good because all value in the list is unique. So
DropdownButtoncan identify which one is selected by your value
Code Example
<code>DropdownButton(
items: answerList.map(
(answer) => DropdownMenuItem(
// So when you iterate this dropdownmenuitem, make sure
// this [value] is unique, no duplicated [answer].
value: answer,
child: Text('$answer'),
),
),
onChanged: onChanged,
)
</code>
<code>DropdownButton(
items: answerList.map(
(answer) => DropdownMenuItem(
// So when you iterate this dropdownmenuitem, make sure
// this [value] is unique, no duplicated [answer].
value: answer,
child: Text('$answer'),
),
),
onChanged: onChanged,
)
</code>
DropdownButton(
items: answerList.map(
(answer) => DropdownMenuItem(
// So when you iterate this dropdownmenuitem, make sure
// this [value] is unique, no duplicated [answer].
value: answer,
child: Text('$answer'),
),
),
onChanged: onChanged,
)