Flutter: Can't add item to list with callback - flutter

Question

In my this file I receive list of Properties from API and generate like this interface:
Problem:
When I tried enter volume and check result then receive null and new property not added to list. I add new property using setProperty callback in my code. All enteren properties will be saved in List<PropertyData> selectedProperties; variable.
Code:
class FarmerPropertyScreen extends StatefulWidget {
final bool isEdit;
FarmerPropertyScreen({Key key, this.isEdit}) : super(key: key);
#override
_FarmerPropertyScreenState createState() => _FarmerPropertyScreenState();
}
class _FarmerPropertyScreenState extends State<FarmerPropertyScreen> {
List<PropertyModel> properties;
ApiDataService apiDataService = getItInstance<ApiDataService>();
List<PropertyData> selectedProperties;
Future getProperties() async {
if (properties == null) {
var res = await apiDataService.getProperties();
if (res != null) {
print("Properties received from API");
setState(() {
properties = res;
});
}
}
}
#override
void initState() {
getProperties();
super.initState();
}
#override
void dispose() {
super.dispose();
}
void setProperty(double volume, int id) {
print("CALLBACK INFO");
print("ID");
print(id);
print("VOLUME");
print(volume);
if (selectedProperties != null && selectedProperties.length > 0) {
print("REMOVED TO UNIQUE LIST");
selectedProperties.removeWhere((item) => item.id == id);
}
if (volume > 0) {
print("ADDED NEW PROPERTY");
setState(() {
selectedProperties.add(PropertyData(id: id, volume: volume));
});
}
}
List<Widget> propertiesList() {
List<Widget> children = [];
if (properties != null && properties.length > 0) {
for (int i = 0; i < properties.length; i++) {
children.add(
FarmerObject(
id: properties[i].id,
title: properties[i].title,
volume: 0.0,
enabled: i == 0 ? true : false,
callback: setProperty,
),
);
if (i != properties.length - 1) {
children.add(
SizedBox(height: MediaQuery.of(context).size.height * 0.02),
);
}
if (i == properties.length - 1) {
children.add(SizedBox(height: 45.h));
children.add(
FlatButton(
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(5.0),
),
minWidth: 206.w,
padding: EdgeInsets.symmetric(vertical: 12.h),
disabledColor: Colors.black12,
disabledTextColor: Colors.blueGrey,
onPressed: () {
print("CHECK ADDED PROPERTIES");
print(selectedProperties);
return null;
},
color: primaryColor,
child: Text(
'Check',
style: TextStyle(
color: Color(0xFF2B2B2B),
fontWeight: FontWeight.w500,
fontSize: 15.sp,
),
),
),
);
children.add(
SizedBox(height: MediaQuery.of(context).size.height * 0.06),
);
}
}
}
return children;
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
elevation: 0,
centerTitle: true,
title: Text(widget.isEdit == true ? 'Edit' : 'Continue'),
),
body: Column(
children: [
widget.isEdit == true
? Container()
: Container(
padding: EdgeInsets.only(
top: 30.h,
left: 25.w,
right: 25.w,
),
child: Column(
children: [
Container(
alignment: Alignment.center,
child: Text(
'Step - 3',
style: TextStyle(
color: Color(0xFF2B2B2B),
fontSize: 14.sp,
),
),
),
SizedBox(height: 35.h),
SignUpHeader('What do you have?', 'give'),
SizedBox(height: 15.h),
],
),
),
Expanded(
child: SingleChildScrollView(
child: Container(
padding: EdgeInsets.only(
top: 10.h,
left: 25.w,
right: 25.w,
),
child: Column(
children: propertiesList(),
),
),
),
),
],
),
);
}
}
class FarmerObject extends StatefulWidget {
final int id;
final String title;
final double volume;
final bool enabled;
final Function(double, int) callback;
FarmerObject({
this.id,
this.volume,
this.callback,
this.title,
this.enabled,
});
#override
_FarmerObjectState createState() => _FarmerObjectState();
}
class _FarmerObjectState extends State<FarmerObject> {
bool status = false;
int divisions;
var priceController = new MoneyMaskedTextController(
decimalSeparator: '.', thousandSeparator: ',');
#override
void initState() {
setState(() {
if (widget.volume != null) {
priceController.updateValue(widget.volume);
}
status = widget.enabled;
});
super.initState();
}
#override
Widget build(BuildContext context) {
return Container(
padding: EdgeInsets.only(left: 10, right: 4),
decoration: BoxDecoration(
color: Colors.white,
borderRadius: BorderRadius.only(
topLeft: Radius.circular(5),
topRight: Radius.circular(5),
bottomLeft: Radius.circular(5),
bottomRight: Radius.circular(5)),
boxShadow: [
BoxShadow(
color: Colors.black.withOpacity(0.25),
spreadRadius: 0,
blurRadius: 2,
offset: Offset(0, 0),
),
],
),
child: Column(
children: [
Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: [
Text(widget.title),
Switch(
value: status,
activeColor: primaryColor,
inactiveThumbColor: Color(0xFFAFAFAF),
onChanged: (bool val) {
setState(() {
status = val;
});
if (val == false || priceController.numberValue == 0) {
widget.callback(0.0, widget.id);
} else {
print("Setted again");
print(priceController.numberValue);
widget.callback(priceController.numberValue, widget.id);
}
})
],
),
status == true
? Column(
children: [
FadeInRight(
duration: Duration(milliseconds: 800),
child: Container(
// alignment: Alignment.centerRight,
decoration: BoxDecoration(
color: Colors.white,
borderRadius: new BorderRadius.circular(5.0),
boxShadow: [
BoxShadow(
color: Colors.white,
// spreadRadius: 1,
// blurRadius: 3,
),
],
),
child: TextFormField(
validator: (value) {
return null;
},
controller: priceController,
onChanged: (val) {
print("VALUE CHANGED!");
double enteredPrice = priceController.numberValue;
widget.callback(enteredPrice, widget.id);
},
keyboardType: TextInputType.number,
textAlign: TextAlign.start,
maxLines: 1,
maxLength: 18,
maxLengthEnforced: true,
decoration: InputDecoration(
isDense: true,
hintText: 'Enter volume',
contentPadding: EdgeInsets.all(0),
counterText: '',
filled: true,
fillColor: Colors.white,
border: OutlineInputBorder(
borderRadius: new BorderRadius.circular(10.0),
borderSide: BorderSide.none,
),
suffixIcon: Padding(
padding: EdgeInsets.all(15),
child: Text(
'volume',
textAlign: TextAlign.right,
style: TextStyle(
color: Color(0xFFAFAFAF),
fontSize: 14.sp,
),
),
),
),
),
),
),
],
)
: SizedBox(height: 0),
],
),
);
}
}
class PropertyData {
final int id;
final double volume;
PropertyData({this.id, this.volume});
}
Maybe my logic is wrong in this file to save new items in the list?

Answer 1

The issue is in List<PropertyData> selectedProperties;
By default, the value in selectedProperties will be null. So, when you are trying to add, it basically fails.
Replace it with, List<PropertyData> selectedProperties = [];