When i choose item in the below list, it does not change. If i click the others,then nothing happens.
How can i change this value both firestore and UI ?
I know, i need to update value: constantValue, this code, but how i can do that with provider?
Here, button:
Widget dropdownButton(BuildContext context) {
String constantValue = "League Of Legends";
return DropdownButton(
value: constantValue,
onChanged: (newValue) {
context.read<PostProvider>().postCategory = newValue;
},
items: <String>["League Of Legends", "Steam", "Csgo"]
.map<DropdownMenuItem<String>>((String value) {
return DropdownMenuItem<String>(
value: value,
child: Text(value),
);
}).toList());
}
and also provider:
String _postCategory;
String get postCategory => _postCategory;
set postCategory(String value) {
_postCategory = value;
notifyListeners();
}
You need to include something to write FireBase in the code path. Provider doesn't magically do that for you. However, you can have various providers or widgets wake up on that notify_listeners() call.
Related
Situation:
I have a checkbox in one place and i am sending the callback etc. up the widget tree to run a setState and run the function applyFilters().
The NeededChecked is also routed up to the checkbox-value.
Question:
What i am struggling to understand is why this works.
Specifically how the onPressed callback is able to set the value of the bool isNeededState to true/false?
Here is the code that is run. The only important part is the passing of the bool isNeededState to the neededCheked.
void neededFilterCalled(bool isNeededState) {
setState(() {
NeededChecked = isNeededState;
applyFilters();
});
}
And here is the checkbox widget:
Widget build(BuildContext context) {
return Checkbox(
value: isNeededChecked,
onChanged: neededFilterCalled,
);
}
Writing
onChanged: neededFilterCalled,
is shorthand for
onChanged: (value) => neededFilterCalled(value),
onChanged provide nullable bool, defined as
required void Function(bool?)? onChanged
You can accept null value and provide false on null case like
void neededFilterCalled(bool? isNeededState) {
setState(() {
isNeededChecked = isNeededState ?? false;
applyFilters();
});
}
return Checkbox(
value: isNeededChecked,
onChanged: neededFilterCalled,
);
This is my drop down list code
String dropdownValue = "a";
#override
Widget build(BuildContext context) {
return DropdownButton<String>(
value: dropdownValue
),
onChanged: (String? newValue) {
setState(() {
dropdownValue = newValue!;
});
},
items: <String>[
'a','b','c'
].map<DropdownMenuItem<String>>((String value) {
return DropdownMenuItem<String>(
value: value,
child: Text(value),
);
}).toList(),
);
}
}
I want to use the selected value here
uploadDatatoFirebase() async {
*firebase connection code*
await FirebaseFirestore.instance
.collection(**selected value in drop down**) // the value from the box goes here
}
I can't seem to find a solution please help i want to create a database depending on the select box value any other techniques will also be welcomed
https://pub.dev/packages/get_it This is the package I use so I can can access a single instance of a class anywhere in the app, it is very popular and very well maintained. You could do this
setState(() {
dropdownValue = newValue!;
GetIt.I.get<ControllerWhatever>().selectedValueInDropDown = newValue!;
})
Just register the 'global controller instance' just as described in the get_it page and you will be able to get the value from any attribute you want anywhere in your app. It will make you life a lot easier
I have 2 DropdownButtonFormFields where I have a selection of cars. I need to change the second selection of buttons according to the car model user has chosen from the first selection in the DropdownButtonFormField (i.e. If a user chooses a Mercedes in the first one, in the DropdownButtonFormField below, I want to display only models of Mercedes and not, let's say, Audi).
How can I achieve this? Here is the code:
String _make, _model;
/// List of cars and models
List<String> carList = [
'Audi',
'BMW',
'Mercedes',
];
List<String> modelAudi = ['A6', 'A8', 'Q7',];
List<String> modelMercedes = ['E-Class', 'S-Class','Maybach'];
List<String> modelBMW = ['3-Series', 'X5', 'X7'];
/*two DropdownButtonFormFields, but the second one needs to match
it's car manufacturer selection from the carList selection
(i.e. if you select Audi, it must only show the modelAudi list (A6,
A8, Q7) in the second DropdownButtonFormField)
*/
DropdownButtonFormField<String>(
value: _make,
items: carList
.map((label) => DropdownMenuItem(
child: Text(label.toString()),
value: label,
))
.toList(),
onChanged: (value) {
setState(() {
_make = value;
print(value);
});
},
),
DropdownButtonFormField<String>(
value: _model,
/* here is where I need to implement logic
that maps out the model names that matches the car maker
*/
items: modelAudi
.map((label) => DropdownMenuItem(
child: Text(label.toString()),
value: label,
))
.toList(),
onChanged: (value) {
setState(() {
_model = value;
print(value);
});
},
),
The DropDown for the first button:
And naturally because I have no logic behind it, I get this as the model selection whatever I chose from the car list, but I want it to map out only models from the car list you chose.
This is a great use case for a switch statement. Define your cases for each car maker according to this example:
String _maker;
List chosenMakerModel;
switch (_maker) {
case 'Audi':
chosenMakerModel = modelAudi;
break;
case 'BMW':
// implement logic:
break;
case 'OTHER MANUFACTURER':
// implement logic;
break;
}
Using the example code above use chosenMakerModel instead of modelAudi
You can create a model selection method to handle this situation, like
List<String> _selectModel(String? modelName) {
return modelName == carList[0]
? modelAudi
: modelName == carList[1]
? modelMercedes
: modelBMW; // initally it will have modelBMW
}
This will decide the second dropdown item. If you click to select the second drop down item 1st, it will through errors. To handle this situation, you need to update the second dropdown value as well. You can set the second dropdown value=null. Therefor we need to use nullable String for selection value.
class MyProfileState extends State<StatefulWidget> {
String? _make, _model;
/// List of cars and models
List<String> carList = ['Audi', 'BMW', 'Mercedes'];
List<String> modelAudi = ['A6', 'A8', 'Q7'];
List<String> modelMercedes = ['E-Class', 'S-Class', 'Maybach'];
List<String> modelBMW = ['3-Series', 'X5', 'X7'];
List<String> _selectModel(String? modelName) {
return modelName == carList[0]
? modelAudi
: modelName == carList[1]
? modelMercedes
: modelBMW;
}
#override
Widget build(BuildContext context) {
return Scaffold(
body: Column(
children: [
DropdownButtonFormField<String>(
value: _make,
items: carList
.map((label) => DropdownMenuItem(
child: Text(label.toString()),
value: label,
))
.toList(),
onChanged: (value) {
setState(() {
_make = value;
_model = null;
print(value);
});
},
),
DropdownButtonFormField<String>(
value: _model,
items: _selectModel(_make)
.map((label) => DropdownMenuItem(
child: Text(label.toString()),
value: label,
))
.toList(),
onChanged: (value) {
setState(() {
_model = value;
print(value);
});
},
),
],
));
}
}
I am sending the choosen value of the DropdownMenu via Callback to the parent widget (see code below).
return DropdownButton<String>(
hint: Text(widget.hint),
value: valueChoose,
items: widget.users.map((dynamic valueItem) {
return DropdownMenuItem<String>(
value: valueItem,
child: Text(valueItem),
);
}).toList(),
onChanged: (newValue) {
setState(() {
valueChoose = newValue;
besetzungsList.add(valueChoose);
widget.besetzungsListChanged(valueChoose);
widget.fromDropDown(true);
});
},
);
The problem is with "besetzungsList[i] = value;" no rebuild occurs. But I need the choosen value to be shown in the UI. If I set the value via the insert function then it works. But I need to replace the value inside the list.
DataCell(DropDown(
hint: "Wählen",
users: users,
besetzungsListChanged: (String value) {
besetzungsList[i] = value;
},
fromDropDown: (bool value) => fromDropDown = value,
))
Is the parent widget a stateful widget?
you can try to call setState in benutzungsListChangedto enforce rebuild of the parent widget
DataCell(DropDown(
hint: "Wählen",
users: users,
besetzungsListChanged: (String value) {
setState(() {besetzungsList[i] = value;});
},
fromDropDown: (bool value) => fromDropDown = value,
))
I am trying to use a dropdown button to have the user select from a list of options, however after making a selection the dropdown button remains displaying the hint. I think something about the setState is not updating the dropdown button.
value: skillChoice,
items: listDrop,
hint: Text("Choose Skill"),
onChanged: (value) {
setState(() {
skillChoice = value;
});
},
),
here are the variables which are declared earlier in the code:
List<DropdownMenuItem<int>> listDrop = [];
int skillChoice = null;
Can anyone let me know why it isn't updating?
I think setting skillChoice null initially disables the dropdown.
It would have been better if you had shown the full code snippet of how you implemented your DropDownButton. But here is how I do implement mine:
// This is the initial value that will be selected on the DropDownMenu by default
String choice = '1';
// This is the List of String (or whatever data type you want) that will make up the
Drop Down Menu Item options. NOTE: That the String value of 'choice' ('1') is also present in the List of choices ('1')
List<String> choices = [
'1',
'2',
'3',
'4',
'5',
];
DropdownButton<String>(
value: choice,
icon: Icon(Icons.add),
onChanged: (String newValue) {
setState(() => choices = newValue);
},
items: choices.map<DropdownMenuItem<String>>((String value) {
return DropdownMenuItem<String>(
value: value,
child: Text(
value,
)
);
}).toList(),
),
Should work properly for you now.