Flutter - Can't pass class field into child component-CodePudding

New to Flutter and I want to start making my app more dynamic. I'd like to start by passing data to my Text() widgets, but I am getting this weird null error and have NO idea why this is.

Currently I am doing this, where I pass in name and view it in the Text widget in the container:

class NameContainer extends StatelessWidget {
const NameContainer({ required this.name, Key? key}) : super(key : key);

final String name;

@override
Widget build(BuildContext context) {
  return Container(
    margin: const EdgeInsets.all(20.0),
    child: const Align(
      alignment: Alignment.center,
      child: Text(
        name,
        textAlign: 
        TextAlign.center, 
        style: const TextStyle(
          fontWeight: FontWeight.bold,
        )
      );
    )
  );
}

However its giving me a A value of type 'Null' can't be assigned to a parameter of type 'String' in a const constructor. Try using a subtype, or removing the keyword error.

BUT, when I remove the Container and return just the Text like this:

class NameContainer extends StatelessWidget {
const NameContainer({ required this.name, Key? key}) : super(key : key);

final String name;

@override
Widget build(BuildContext context) {

  return Text(
    name,
    textAlign: 
    TextAlign.center, 
    style: const TextStyle(
      fontWeight: FontWeight.bold,
    )
  );
}

Its all good to go? I dont see the difference here... Can anyone share some insight on why this is?

CodePudding user response：

You got the error because you used const keyword before Align widget and Align widget isn't constructor type.

class NameContainer extends StatelessWidget {
 NameContainer({ required this.name, Key? key}) : super(key : key); // const remove from here 

final String name;

@override
Widget build(BuildContext context) {
  return Container(
    margin: const EdgeInsets.all(20.0),
    child:  Align( // here remove const
      alignment: Alignment.center,
      child: Text(
        name,
        textAlign: 
        TextAlign.center, 
        style: const TextStyle(
          fontWeight: FontWeight.bold,
        )
      )
    )
  );
}