Range Error keeps appearing when dismissible widget is run - flutter

Question

Here is my code
import 'package:flutter/material.dart';
void main() => runApp(TodoList());
class TodoList extends StatefulWidget {
#override
State<StatefulWidget> createState() {
// TODO: implement createState
return _TodoListState();
}
}
var TaskTextField;
List taskTextList = [];
var TaskIsImportant = false;
class _TodoListState extends State<TodoList> {
#override
Widget build(BuildContext context) {
// TODO: implement build
return MaterialApp(
title: "To-Do List V2",
home: Scaffold(
appBar: AppBar(
title: Text("To-Do List V2"),
),
body: Flex(
direction: Axis.vertical,
children: <Widget>[
Flexible(
fit: FlexFit.tight,
child: Column(children: <Widget>[
Container(
child: TextField(
decoration: InputDecoration(
hintText: "Enter title of task to be added"),
onChanged: (taskTextField) {
setState(() {
TaskTextField = taskTextField;
print(TaskTextField);
});
},
),
margin: EdgeInsets.all(16.0),
),
CheckboxListTile(
title: Text("Important"),
activeColor: Colors.blue,
value: TaskIsImportant,
onChanged: (val) {
setState(() {
TaskIsImportant = !TaskIsImportant;
print(TaskIsImportant);
});
},
),
Text(
"Tip: Tap on your task to remove it",
style: TextStyle(fontSize: 15.0),
),
Container(
margin: EdgeInsetsDirectional.fromSTEB(117, 10, 117, 5),
child: Row(
children: <Widget>[
RaisedButton(
child: Icon(Icons.add),
onPressed: () {
setState(() {
if (TaskIsImportant) {
taskTextList.add("❗️$TaskTextField");
//taskTitleList.add(TaskDetailField);
} else {
taskTextList.add(TaskTextField);
//taskTitleList.add(TaskDetailField);
}
});
},
),
RaisedButton(
child: Icon(Icons.done_all),
onPressed: () {
setState(() {
taskTextList = [];
});
},
),
],
),
),
Expanded(
child: ListView.builder(
itemBuilder: (context, index) {
var title = taskTextList[index];
padding:
EdgeInsets.all(16.0);
return Dismissible(
key: Key(title[index]),
onDismissed: (direction) {
setState(() {
taskTextList.remove(title);
});
},
child: ListTile(
title: Text(
title,
style: TextStyle(fontSize: 20.0),
),
),
);
},
itemCount: taskTextList.length,
),
)
]),
),
],
)));
}
}
When I create four listTiles in the emulator, two errors are given as follows
flutter: ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
flutter: The following RangeError was thrown building:
flutter: RangeError (index): Invalid value: Not in range 0..3, inclusive: 4
I hope someone can tell me what is wrong with my code. I am running on flutter version 1.3.10. Thanks in advance.
Also to the person that needs more code, here is the full code of main.dart. Hope this will help you find my errors

Answer 1

You are using title[index] but saving the value in title as title = taskTextList[index] which is not an array. So, you are getting range error.