Flutter Customer Painter inside a Stepper Causing Infinite Loop - flutter

Question

I am having an issue with my CustomePainter in a Stepper. It is constantly reloading after the page is loaded and causing an error I am unsure of how to fix.
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return const MaterialApp(
home: MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
const MyHomePage({Key? key}) : super(key: key);
#override
State<MyHomePage> createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
int currentStep = 0;
List<LayoutBuilderWidget> listDynamic = [];
addDynamic() {
numberofwalls ++;
listDynamic.add(LayoutBuilderWidget(numberofwalls));
LengthFT = [];
LengthIN = [];
Angle = [];
setState(() {
});
}
submitdata(){
double MathLengthFT;
double finalLength;
LengthFT = [];
LengthIN = [];
Angle = [];
listDynamic.forEach((widget) => LengthFT.add(widget.lengthFT.text));
listDynamic.forEach((widget) => LengthIN.add(widget.lengthIN.text));
listDynamic.forEach((widget) => Angle.add(widget.dropdownValue));
for(int i=0; i < numberofwalls; i++)
{
if(LengthIN[i] == null)
{
double MathLengthFT = int.parse(LengthFT[i]) * 12;
FinalLength.add(MathLengthFT.toString());
}
if(LengthFT[i] == null)
{
finalLength = double.parse(LengthIN[i]);
FinalLength.add(finalLength.toString());
}
MathLengthFT = int.parse(LengthFT[i]) * 12;
finalLength = int.parse(LengthIN[i]) + MathLengthFT;
FinalLength.add(finalLength.toString());
}
}
#override
Widget build(BuildContext context) {
return Scaffold(
body:Stepper(
type: StepperType.horizontal,
steps: getSteps(),
currentStep: currentStep,
onStepContinue: () {
final isLastStep = currentStep == getSteps().length - 1;
if(isLastStep){
print('Complete');
//Send Data to Database
}
else{
setState(() {
currentStep += 1;
});
}
},
onStepCancel:
currentStep == 0 ? null : () => setState(() => currentStep -= 1),
),
);
}
List<Step> getSteps() => [
Step(
isActive: currentStep >= 0,
title: const Text('Layout'),
content: Container(
child: Row(
children: [
Container(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Row(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Container(
alignment: Alignment.center,
margin: const EdgeInsets.all(20),
width: 200,
child: Text(
'Wall',
style: Theme.of(context).textTheme.headline4,
),
),
Container(
alignment: Alignment.center,
margin: const EdgeInsets.all(20),
width: 200,
child: Text(
'Length',
style: Theme.of(context).textTheme.headline4,
),
),
Container(
alignment: Alignment.center,
margin: const EdgeInsets.all(20),
width: 200,
child: Text(
'Angle',
style: Theme.of(context).textTheme.headline4,
),
),
],
),
Container(
height: 600,
width: 1000,
child: ListView.builder(
itemCount: listDynamic.length,
itemBuilder: ((_, index) => listDynamic[index])
)
),
FloatingActionButton.extended(onPressed: () => addDynamic(), label: const Text('Add Wall'), icon: const Icon(Icons.add),),
FloatingActionButton.extended(onPressed: () {submitdata();}, icon: const Icon(Icons.visibility), label: const Text(''),),
],
),
),
Column(
children: [
Container(
color: Color.fromARGB(255, 241, 241, 241),
width: 450,
height: 450,
child: CustomPaint(
foregroundPainter: OpenPainter(),
),
),
Container(
margin: EdgeInsets.only(top: 20),
width: 450,
height: 450,
child: CustomPaint(
painter: CanvasLegend(),
),
),
],
)
],
),
),
),
Step(
isActive: currentStep >= 1,
title: const Text('Doors & Options'),
content: Container(
),
Step(
isActive: currentStep >= 2,
title: const Text('Panel Config'),
content: Container(),
),
Step(
isActive: currentStep >= 3,
title: const Text('Accessories'),
content: Container(),
),
Step(
isActive: currentStep >= 4,
title: const Text('Summary & Prices'),
content: Container(),
),
];
}
This snipit consists of the entire stepper method with a layout builder allowing users to add walls to the drawing they display in the painter.
class OpenPainter extends CustomPainter {
OpenPainter();
#override
void paint(Canvas canvas, Size size) {
var line1 = Paint()..strokeWidth = 5;
var line2 = Paint()..strokeWidth = 5;
double lastXPosition = 225;
double lastYPosition = 225;
double NextXPosition = 225;
double NextYPosition = 225;
int i = 0;
if(numberofwalls != 0){
for(i = 0; i < numberofwalls; i++)
{
NextYPosition = lastYPosition + double.parse(FinalLength[i]) * cos(AngleToRadians(double.parse(Angle[i])));
NextXPosition = lastXPosition + double.parse(FinalLength[i]) * sin(AngleToRadians(double.parse(Angle[i])));
canvas.drawLine(
Offset(lastXPosition,lastYPosition),
Offset(NextXPosition, NextYPosition),
line1,
);
lastYPosition = NextYPosition;
lastXPosition = NextXPosition;
}
i = 0;
}
}
#override
bool shouldRepaint(CustomPainter oldDelegate) => true;
}
double AngleToRadians(double angle){
return (pi / 180) * angle;
}
This snipit consists of the entire CustomerPainter with the loop to run through every wall that is added to the forum and display a line representation for the user.
Application view
The attached picture shows the users view when loading into the website.
The error that is showing up is: Another exception was thrown: RangeError (index): Index out of range: no indices are valid: 0.
This error seems to be infinitely repeating once a button is pressed but no loops seem to have a chance to be infinite

Answer 1

Start lists with 0 in Lists and clear out after first wall has been drawn and move first wall back to [0]. This will allow all functions to run correctly.