How to add String to Dropdownbutton - flutter

Question

I have map<dynamic, String> with units and names.
Map timeUnits = <dynamic, String>{
TimeUnit.second: 'second',
TimeUnit.minute: 'minute',
TimeUnit.hour: 'hour',
TimeUnit.day: 'day',
TimeUnit.week: 'week',
TimeUnit.month: 'month',
TimeUnit.calendarYear: 'year',
};
How to add String to Dropdownbutton? Dropdownbutton shows this problem "The argument type 'Map<dynamic, dynamic>' can't be assigned to the parameter type 'List'."
Dropdownbutton code:
child: DropdownButton(
isExpanded: true,
underline: Container(),
value: currentUnits[widget.convertorType],
icon: Padding(
padding: const EdgeInsets.only(right: 8.0, bottom: 6),
child: Image.asset("assets/icons/down-arrow2.png"),
),
iconSize: 35,
elevation: 20,
style: TextStyle(
fontSize: 18,
color: Color.fromRGBO(114,137,218, 1)
),
items: widget.items
.map(
(e) => DropdownMenuItem(
child: e == TimeUnit.calendarYear
? Text("year")
: e.toString().length == 3
? Text(e)
: Text(e.toString().split(".")[1]),
value: e,
),
)
.toList(),
onChanged: (newValue) {
setState(() {
updateCurrentUnit(widget.convertorType, newValue);
widget.calculate();
});
},
),

Answer 1

As per my understanding, it is due to the (items: widget.item) error
so change it to (items: widget.items.entries) and e to e.key or e.value
DropdownButton(
isExpanded: true,
underline: Container(),
value: currentUnits[widget.convertorType],
icon: Padding(
padding: const EdgeInsets.only(right: 8.0, bottom: 6),
child: Image.asset("assets/icons/down-arrow2.png"),
),
iconSize: 35,
elevation: 20,
style: TextStyle(
fontSize: 18,
color: Color.fromRGBO(114,137,218, 1)
),
items: widget.items.entries
.map(
(e) => DropdownMenuItem(
child: e.key == TimeUnit.calendarYear
? Text("year")
: e.toString().length == 3
? Text(e.key)
: Text(e.value),
value: e,
),
)
.toList(),
onChanged: (newValue) {
setState(() {
updateCurrentUnit(widget.convertorType, newValue);
widget.calculate();
});
},
)

Answer 2

first, you have to convert your Map to a list then create a list of dropDownMenuItem and then send it over to dropdown widget
for example in the code below provinces is a list and provincesItems is a List of dropdownMenueItem, i fill provincesItems with items I desire from provinces list and then send it over to dropDown Widget
for (int i = 0; i < provinces.length; i++) {
provincesItems.add(DropdownMenuItem(
value: i,
child: Column(
children: [
Text(
provinces[i].persianName,
style: TextStyle(
color: Colors.black, fontWeight: FontWeight.normal),
),
],
),
));
}