Flutter Exception - Invalid number (at character 1) TextFormField - flutter

Question

I'm trying to display a scaffold msg when user inputted a value greater than some other value...
It is working fine until I clear the input...
After clearing the input it throws an exception...
Here it is...
══╡ EXCEPTION CAUGHT BY WIDGETS ╞═══════════════════════════════════════════════════════════════════
The following FormatException was thrown while calling onChanged:
Invalid number (at character 1)
^
When the exception was thrown, this was the stack:
#0 int._handleFormatError (dart:core-patch/integers_patch.dart:129:7)
#1 int.parse (dart:core-patch/integers_patch.dart:55:14)
#2 _GeneralTabState.build.<anonymous closure>.<anonymous closure>
(package:shop_app_vendor/screens/add_products/general_tab.dart:247:25)
#3 new TextFormField.<anonymous closure>.onChangedHandler (package:flutter/src/material/text_form_field.dart:188:25)
#4 EditableTextState._formatAndSetValue (package:flutter/src/widgets/editable_text.dart:2630:27)
#5 EditableTextState.userUpdateTextEditingValue (package:flutter/src/widgets/editable_text.dart:2919:5)
#6 EditableTextState._replaceText (package:flutter/src/widgets/editable_text.dart:3144:5)
#7 CallbackAction.invoke (package:flutter/src/widgets/actions.dart:534:39)
#8 ActionDispatcher.invokeAction (package:flutter/src/widgets/actions.dart:573:21)
#9 Actions.invoke.<anonymous closure> (package:flutter/src/widgets/actions.dart:872:48)
#10 Actions._visitActionsAncestors (package:flutter/src/widgets/actions.dart:653:18)
#11 Actions.invoke (package:flutter/src/widgets/actions.dart:866:30)
#12 _DeleteTextAction.invoke (package:flutter/src/widgets/editable_text.dart:4042:20)
#13 _OverridableContextAction.invokeDefaultAction (package:flutter/src/widgets/actions.dart:1696:28)
#14 _OverridableActionMixin.invoke (package:flutter/src/widgets/actions.dart:1559:9)
#15 ActionDispatcher.invokeAction (package:flutter/src/widgets/actions.dart:571:21)
#16 ShortcutManager.handleKeypress (package:flutter/src/widgets/shortcuts.dart:755:38)
#17 _ShortcutsState._handleOnKey (package:flutter/src/widgets/shortcuts.dart:956:20)
#18 FocusManager._handleKeyMessage (package:flutter/src/widgets/focus_manager.dart:1687:32)
#19 KeyEventManager._dispatchKeyMessage (package:flutter/src/services/hardware_keyboard.dart:828:34)
#20 KeyEventManager.handleRawKeyMessage (package:flutter/src/services/hardware_keyboard.dart:875:15)
#21 BasicMessageChannel.setMessageHandler.<anonymous closure> (package:flutter/src/services/platform_channel.dart:77:49)
#22 BasicMessageChannel.setMessageHandler.<anonymous closure> (package:flutter/src/services/platform_channel.dart:76:47)
#23 _DefaultBinaryMessenger.setMessageHandler.<anonymous closure> (package:flutter/src/services/binding.dart:380:35)
#24 _DefaultBinaryMessenger.setMessageHandler.<anonymous closure> (package:flutter/src/services/binding.dart:377:46)
#25 _invoke2.<anonymous closure> (dart:ui/hooks.dart:190:15)
#29 _invoke2 (dart:ui/hooks.dart:189:10)
#30 _ChannelCallbackRecord.invoke (dart:ui/channel_buffers.dart:42:5)
#31 _Channel.push (dart:ui/channel_buffers.dart:132:31)
#32 ChannelBuffers.push (dart:ui/channel_buffers.dart:329:17)
#33 PlatformDispatcher._dispatchPlatformMessage (dart:ui/platform_dispatcher.dart:589:22)
#34 _dispatchPlatformMessage (dart:ui/hooks.dart:89:31)
(elided 3 frames from dart:async)
════════════════════════════════════════════════════════════════════════════════════════════════════
And here's my code...
scf.dart
class SCF {
scaffoldMsg({context, msg}) {
ScaffoldMessenger.of(context).showSnackBar(SnackBar(
content: Text(msg),
backgroundColor: Colors.red,
action: SnackBarAction(
label: 'OK',
textColor: Colors.white,
onPressed: () {
ScaffoldMessenger.of(context).clearSnackBars();
},
),
));
}
}
general_tab.dart
class GeneralTab extends StatefulWidget {
const GeneralTab({Key? key}) : super(key: key);
#override
State<GeneralTab> createState() => _GeneralTabState();
}
class _GeneralTabState extends State<GeneralTab> {
final SCF _scf = SCF();
#override
Widget build(BuildContext context) {
return Consumer<ProductProvider>(
builder: (context, provider, child) {
return ListView(
padding: const EdgeInsets.all(15.0),
children: [
// Regular Price
FormFieldInput(
label: 'Regular Price',
inputType: TextInputType.number,
onChanged: (value) {
provider.getFormData(regularPrice: int.parse(value));
},
),
// Sales Price
FormFieldInput(
label: 'Sales Price',
inputType: TextInputType.number,
onChanged: (value) {
if (int.parse(value) > provider.productData!['regularPrice']) {
_scf.scaffoldMsg(
context: context,
msg: 'Sales price should be less than regular price',
);
}
setState(() {
provider.getFormData(salesPrice: int.parse(value));
});
},
),
],
);
},
);
}
}
product_provider.dart
class ProductProvider with ChangeNotifier {
Map<String, dynamic>? productData = {};
getFormData({
int? regularPrice,
int? salesPrice,
}) {
if (regularPrice != null) {
productData!['regularPrice'] = regularPrice;
}
if (salesPrice != null) {
productData!['salesPrice'] = salesPrice;
}
notifyListeners();
}
}
form_field.dart
class FormFieldInput extends StatelessWidget {
final String? label;
final void Function(String)? onChanged;
final TextInputType? inputType;
const FormFieldInput({
Key? key,
this.label,
this.onChanged,
}) : super(key: key);
#override
Widget build(BuildContext context) {
return TextFormField(
decoration: InputDecoration(
label: Text(label!),
),
onChanged: onChanged,
);
}
}
This is working fine and showing scaffold msg until I delete the content in the input...
So how can I fix this?

Answer 1

that's because when the the text is empty the app cast the empty to number so this error happened when you reach the compare , so you need to check if the text is not empty before you trigger the compare.
so in your case in the onChange function before trigger any logic ,make sure that the value in the text field is not null or empty.

Answer 2

I found a solution.
By adding if(value.isNotEmpty) to the on change error is gone...
Need to check whether value is empty or not.
That's how I solved my problem.
Thank you
general_tab.dart
class GeneralTab extends StatefulWidget {
const GeneralTab({Key? key}) : super(key: key);
#override
State<GeneralTab> createState() => _GeneralTabState();
}
class _GeneralTabState extends State<GeneralTab> {
final SCF _scf = SCF();
#override
Widget build(BuildContext context) {
return Consumer<ProductProvider>(
builder: (context, provider, child) {
return ListView(
padding: const EdgeInsets.all(15.0),
children: [
// Regular Price
FormFieldInput(
label: 'Regular Price',
inputType: TextInputType.number,
onChanged: (value) {
if (value.isNotEmpty) {
provider.getFormData(regularPrice: int.parse(value));
}
},
),
// Sales Price
FormFieldInput(
label: 'Sales Price',
inputType: TextInputType.number,
onChanged: (value) {
if (value.isNotEmpty) {
if (int.parse(value) > provider.productData!['regularPrice']) {
_scf.scaffoldMsg(
context: context,
msg: 'Sales price should be less than regular price',
);
}
}
setState(() {
provider.getFormData(salesPrice: int.parse(value));
});
},
),
],
);
},
);
}
}