Populating dropdown menu with data from sqlite database in flutter - sqlite

Question

I am working on a list app and want to load the categories of tasks of the home page in the dropdown menu button.
I have used SQflite to save the categories in a table.
When I tap the Dropdown Menu, the values seem not to be loaded on the menu. It's just an empty list.
Here is the code:
class _HomeState extends State<Home> {
TodoService _todoService;
var _selectedValue;
var _categories = List<DropdownMenuItem>();
List<Todo>_todoList=List<Todo>();
final GlobalKey<ScaffoldState> _globalKey=GlobalKey<ScaffoldState>();
#override
initState(){
super.initState();
getAllTodos();
}
_loadCategories() async {
var _categoryService = CategoryService();
var categories = await _categoryService.readCategory();
categories.forEach((category) {
setState(() {
_categories.add(DropdownMenuItem(
child: Text(category['name']),
value: category['name'],
));
});
});
}
getAllTodos()async{
_todoService=TodoService();
_todoList=List<Todo>();
var todos= await _todoService.readTodo();
todos.forEach((todo){
setState(() {
var model=Todo();
model.id=todo['id'];
model.title=todo['title'];
model.dueDate=todo['dueDate'];
model.category=todo['category'];
model.isFinished=todo['isFinished'];
_todoList.add(model);
});
});
}
#override
Widget build(BuildContext context) {
return Scaffold(
key: _globalKey,
appBar: AppBar(
actions: <Widget>[
DropdownButton(
value: _selectedValue,
items: _categories,
onChanged: (value) {
setState(() {
_selectedValue = value;
_loadCategories();
});
},
),

Answer 1

Have you checked the service calls?
Maybe, the SQFlite database is not populated with the values you are trying to retrieve.
Try with a dummy set of values first, like:
items: <String>['One', 'Two', 'Free', 'Four']
.map<DropdownMenuItem<String>>((String value) {
return DropdownMenuItem<String>(
value: value,
child: Text(value),
);
}).toList(),
If the above works, make sure you populate the table by calling an insert query via the service call.
Or you can use the SQFlite's build-in support for doing a raw insert. This means that you can use a SQL string using rawInsert().

Answer 2

You forgot to map the List<Object> in the items of DropdownButton.
DropdownButton _dropdownButton(List<Object> categoriesList) {
return DropdownButton(
value: _selectedValue,
onChanged: (dynamic newValue) {
setState(() {
_selectedValue = newValue;
});
},
items: categoriesList
.map<DropdownMenuItem<Object>>((Object value) {
return DropdownMenuItem<Object>(
value: value,
child: Text(value.getTxt()), // Replace this with getter for the value you want to display
);
}).toList(),
);
}