How to change default value of dropdownButton in flutter?

Question

I`m creating a dropdown button in flutter, but i have a problem when i use dropdown it shows the name of the first item but i want to change it(default value) to categories and idk how to do that, also i tried to use hint(as you see in codes)but it didn't work. here is my codes:

Container(
            height: pageHeight / 15,
            padding: EdgeInsets.all(20),
            child:DropdownButton(
                value: _value,
                items: const [
                  DropdownMenuItem(
                    child: Text("First Item"),
                    value: 1,
                  ),
                  DropdownMenuItem(
                    child: Text("Second Item"),
                    value: 2,
                  ),
                ],
                onChanged: (value) {
                  setState(() {
                    _value = value as int ;
                  });
                },
                hint:Text("Select item")
            ),
          )

I want to change this First Item to categories

Can you please be clearer? – The Chinky Sight Nov 02 '21 at 08:41 — The Chinky Sight, Nov 02 '21 at 08:41
share extra code and what do you exact want – Ravindra S. Patil Nov 02 '21 at 08:44 — Ravindra S. Patil, Nov 02 '21 at 08:44

score 1 · Accepted Answer · answered Nov 02 '21 at 08:53

1

Make value nullable. DropdownButton can have null value and while it is null it will show hint widget.

  int? _value;

DropdownButton(
                  value: _value,
                  items: const [
                    DropdownMenuItem(
                      child: Text("First Item"),
                      value: 1,
                    ),
                    DropdownMenuItem(
                      child: Text("Second Item"),
                      value: 2,
                    ),
                  ],
                  onChanged: (value) {
                    setState(() {
                      _value = value as int;
                    });
                  },
                  hint: Text("categories"),
                ),

answered Nov 02 '21 at 08:53

Md. Yeasin Sheikh

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that's right my value was : `int? _value=1;` – Navid Shokoufeh Nov 02 '21 at 08:57
Yap it was having initial value as 1, that why you were always having 1st item as selected. – Md. Yeasin Sheikh Nov 02 '21 at 08:59
Exception occured. `Exception has occurred. _AssertionError ('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': There should be exactly one item with [DropdownButton]'s value: . Either zero or 2 or more [DropdownMenuItem]s were detected with the same value)` – Dev Conductor Aug 10 '23 at 13:41
1

@DevConductor can you share the link of your question? – Md. Yeasin Sheikh Aug 10 '23 at 17:50
@Md. Yeasin Sheikh. Thanks for your reply. I fixed my issue. – Dev Conductor Aug 10 '23 at 18:01

score 0 · Answer 2 · edited Jun 18 '23 at 00:53

Just Asign on initState()

selectedDropDownValue = "categories";

Container(
            height: pageHeight / 15,
            padding: EdgeInsets.all(20),
            child:DropdownButton(
                items: const [
                  DropdownMenuItem(
                    child: Text("First Item"),
                    value: 1,
                  ),
                  DropdownMenuItem(
                    child: Text("Second Item"),
                    value: 2,
                  ),
                ],
                value: selectedDropDownValue, 
                onChanged: (value) {
                  setState(() {
                    selectedDropDownValue = value;
                  });
                },
                hint:Text("Select item")
            ),
          )

How to change default value of dropdownButton in flutter?

2 Answers2