I'm back with another issue with the DropdownButton.
The DropdownButton is not enabled. I found this in api.flutter.dev
If the onChanged callback is null or the list of items is null then
the dropdown button will be disabled, i.e. its arrow will be displayed
in grey and it will not respond to input.
Here is my code now:
return new DropdownButton<String>(
hint: new Text("Select Agency"),
value: _currentAgency,
onChanged: changedDropDownAgency,
items: snapshot.data.docs.forEach((document) {
return new DropdownMenuItem<String>(
value: document.data()['name'],
child: new Text(document.data()['name']),
);
}),
);
void changedDropDownAgency(String selected_agency) {
setState(() {
_currentAgency = selected_agency;
});
globals.selectedAgency = selected_agency;
}
The forEach loop runs fine and in debug mode I can see that there is data in the document object. I don't know how to debug the DropdownButton code to see why the button is not active. Any suggestions would be helpful.
Thanks.
forEach() on Iterables does not return any value (see: https://api.dart.dev/stable/2.10.5/dart-core/Iterable/forEach.html), and thus items is null and the DropdownButton is disabled. Use map instead (https://api.dart.dev/stable/2.10.5/dart-core/Iterable/map.html). Example:
snapshot.data.docs.map<DropdownMenuItem<String>>((document) {
return new DropdownMenuItem<String>(
value: document.data()['name'],
child: new Text(document.data()['name']),
);
}).toList(),
Related
So I have a ListView with Checkboxes
bool checked = false;
ListView.builder(
itemCount: logs!.length,
itemBuilder: (context, index) {
Log log = logs[index];
return ExpansionTile(
title:
Checkbox(
value: checked,
onChanged: (curValue) {
checked = curValue;
setState(() {});
}),
)
],
)
},
);
The problem is that when I check one Box in the List, all values are changed, because the variable is global & therefore the same boolean is appended to all checkboxes.
When I pack the boolean inside the ListView, I cant click on the Checkbox at all -> because of the setState the value is always reseted & no change appears
So what can I do to make all Checkboxes clickable without influencing the click state of the other ones?
Since you have only 1 variable to check the state of the checkbox, all other checkbox widgets will also depend on this checked variable.
You have to define for every checkbox a own "checked" variable, you could add a checked variable to the Log class and then query and set it each time.
Checkbox(
value: logs[index].checked,
onChanged: (curValue) {
logs[index].checked = curValue;
setState(() {});
},
),
The issue is here using single variable for all items. You can use a List for selected item
List<Log> selectedLogs = [];
Checkbox(
value: selectedLogs.contains(log),
onChanged: (curValue) {
if(selectedLogs.contains(log)){
selectedLogs.remove(log);
}else {
selectedLogs.add(log);
}
setState(() {});
}),
)
I am using the flutter pref library to create a settings page. The PrefChoice is used to show a drop down for language selection. The drop down shows the values properly. Issue is when we select anything from the drop down, the onChange method does not get called for some reason. Due to this we are not able to take action on the change in choice. Is there anything I am missing here?
PrefChoice<String>(
title: Text(AppLocalization.of(context, 'settings.language')),
pref: 'language_key',
items: const [
DropdownMenuItem(
value: LocaleConstants.LC_ENGLISH,
child: Text(LocaleConstants.ENGLISH)),
DropdownMenuItem(
value: LocaleConstants.LC_GERMAN,
child: Text(LocaleConstants.GERMAN))
],
onChange: (value) {
// This never gets called
log.d('Locale changed to - $value');
},
),
I created a dropdownButton to allow users to select from a dropdown list which will be populated from an API. For now I am populating using a list I created.
Currently the button is displaying the items from my list but after a selection has been made the list doesnt show the selected item and still shows the hint text. What I would like to happen is after a selection has been made then the dropdownButton shows the item that was selected instead of the hint text.
in the onChanged method I added a setState in hopes of updating the _selectedValue variable to the value that was selected and displaying it in the dropdownButton.
I also added a print statement in my setState method and that does trigger and show me the value within the value variable.
Here is my code.
List<DropdownMenuItem<int>> listItems = [DropdownMenuItem(child: Text("2016"), value: 2016,), DropdownMenuItem(child: Text("2021"), value: 2021,)];
int _selectedValue;
body: DropdownButton(
value: _selectedValue,
items: listItems,
hint: Text("Select Year"),
onChanged: (int value){
setState(() {
_selectedValue = value;
print(value);
});
},
),
Your code is fine, but the problem is maybe you are initializing the _selectedValue inside the build() method. So that whenever you call set state the widget rebuilds and initialize again with the default value.
int _selectedValue;
#override
Widget build(BuildContext context) {
return DropdownButton(
value: _selectedValue,
items: listItems,
hint: Text("Select Year"),
onChanged: (int value){
setState(() {
_selectedValue = value;
print(value);
});
},
),
In case anyone else is having this issue, I had the same issue and it was driving me nuts and I was using setState() appropriately etc., It was 100% where I was defining the "initialValue" property.
I was defining it right inside the build method. That did not work, even though I had the same setup in a sister module and it indeed did work. Not sure why that is.
Once I changed the definition of that variable to the state class, it worked like a charm. Hope it saves some, some cycles.
When I select a value from my dropdown the hint text does not change:
String fontSizeValue;
new DropdownButton<String>(
items: new List<double>.generate(72, (i) => i + 2.0).map((double value) {
return new DropdownMenuItem<String>(
value: value.toString(),
child: new Text(value.toString()),
);
}).toList(),
onChanged: (String _) {
setState(() {
fontSize = double.parse(_);
fontSizeValue = _;
print(fontSizeValue);
});
},
value: fontSizeValue,
hint: Text('Select'),
)),
],
),
),
);
Any idea how I can get the selected value to show instead of "select"? Thanks
You did not post enough code, but I'll take a wild guess anyway, because there are a lot of questions with this problem:
Your variable String fontSizeValue; is defined locally, probably in the build function.
You have to define it in a wider scope, so it will retain it's value after another call to build that will happen when you call setState. Probably as a class member of your State class.
My dropdown menu works properly after selecting a new option, but the new selection doesn't update the currently displayed option after its changed.
Widget buildCarDropdown() {
return
Center(
child: DropdownButton(
hint: Text('Please choose a car make'),
value: currentLease.carMake,
onChanged: (newValue) {
setState(() {
currentLease.carMake = newValue;
});
},
items: carMakes.map((String make) {
return DropdownMenuItem(
child: new Text(make),
value: make,
);
}).toList(),
),
);
}
carMakes is just an array of strings
currentLease contains a string for the selection of make. The value is set correctly after changing it in currentLease, and displays correctly if the widget is reloaded.
Everything seems proper here to me, not sure why it doesn't display updates properly.
Edit: What I mean by not updating it, that the drop down opens displaying all the options. Say it started at "Honda", you can then select "Acura" and though the currentLease.carMake gets updated properly, the drop down stays displaying "Honda" until it is reloaded.