I want to set default function in my child Widget in a constructor.

Basically, I have two widgets

1. Login (Parent Widget)
2. AppButton (Child Widget)

Here is my AppButton.dart

And I am calling this child widget in Login.dart (Parent) like this:

AppButton(title: "Login")

Please give me a way that to set default function without making "onPress" required for it's Parent (Login.dart)

TIA

CodePudding user response：

Only static value can be set as default value in constructor, so you need define you function as static like this:

class AppButton extends StatefulWidget {
  final Function onPress;
  const AppButton({Key? key, this.onPress = _onPress}) : super(key: key);
  
  static void _onPress(){}

  @override
  State<AppButton> createState() => _AppButtonState();
}

CodePudding user response：

just make it nullable:

 class MyButton extends StatefulWidget {
  final void Function()? onPress;
  final String title;
  const MyButton({Key? key, this.onPress, required this.title}) : super(key: key);

  @override
  State<MyButton> createState() => _MyButtonState();
}

class _MyButtonState extends State<MyButton> {

  void Function() defaultOnPress = (){
    // your default function here
  };

  @override
  Widget build(BuildContext context) {
    return ElevatedButton(onPressed: widget.onPress ?? defaultOnPress, child: const Text("my button"));
  }
}

still you can get const constructor