Flutter-GetX Error: The parameter 'index' can't have a value of 'null' beca-CodePudding

1 I am very new to Dart, and coding in general. I have produced this code after watching tutorials on YouTube. For the most part, I have been able to troubleshoot most of my problems on my own, yet I cannot figure out my most recent errors. When I try to right the variable in a stateless widget the following error occurs.

The parameter 'index' can't have a value of 'null' because of its type, but the implicit default value is 'null'.

the code is:

class TodoScreen extends StatelessWidget {

final TodoController todoController = Get.find();
int index;
TodoScreen({this.index});



@override
Widget build(BuildContext context) {
String? text ='';
if(this.index != null){

  text = todoController.todos[index].text;

}
TextEditingController textEditingController = TextEditingController();
return Scaffold(
  body: Container(
    padding: const EdgeInsets.all(20.0),
    child: Column(
      children: [
        Expanded(
          child: TextField(
            controller: textEditingController,
            autofocus: true,
            decoration: const InputDecoration(
                hintText: 'What do you want to accomplish',
                border: InputBorder.none,
                focusedBorder: InputBorder.none),
            style: TextStyle(fontSize: 25.0),
            keyboardType: TextInputType.multiline,
            maxLines: 999,
          ),
        ),
        Row(
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          children: [
            ElevatedButton(
              onPressed: () {Get.back();},
              child: const Text("Cancle"),
              style: ButtonStyle(
                backgroundColor: MaterialStateProperty.all(Colors.red),
              ),
            ),
            ElevatedButton(
              onPressed: () {
                todoController.todos.add(Todo(text: textEditingController.text), ); Get.back();

              },
              child: const Text("Add"),
              style: ButtonStyle(
                backgroundColor: MaterialStateProperty.all(Colors.green),
              ),
            )
          ],
        ),
      ],
    ),
  ),
);
}
[![enter image description here][1]][1]}

and when I change

final TodoController todoController = Get.find();
int? index;
TodoScreen({this.index});

constructor is fine now but

text = todoController.todos[index].text;

has to following error

The argument type 'int?' can't be assigned to the parameter type 'int'.

can someone please find what is wrong here?

CodePudding user response：

this error occurs because null_safety wants to tell you that this int can be null, but is absolutely necessary here where you want to use it, that means: the int must have a value

you can solve the problem by putting a '!' after the index name

text = todoController.todos[index!].text;

CodePudding user response：

Your Code

class TodoScreen extends StatelessWidget {

final TodoController todoController = Get.find();
int index;
TodoScreen({this.index});



@override
Widget build(BuildContext context) {
String? text ='';
if(this.index != null){

  text = todoController.todos[index].text;

}

update code

class TodoScreen extends StatelessWidget {
    
    final TodoController todoController = Get.find();
    int? index;
    TodoScreen({this.index});
    
    
    
    @override
    Widget build(BuildContext context) {
    String? text ='';
    if(this.index != null){
    
      text = todoController.todos[index].text;
    
    }