how to use callback function with value in flutter?

Question

I wanted to allow a class that have a callback that passes back data to the main class.

So there is two class: First class contain the body of another widget from other class and a save button. The second class is the widget class stores in another file.

How to I save the value that had been inputted in the second class after i click the save button?

Answer 1

Can't you just do:

class WidgetWithCallback {
  VoidCallback onButtonPressed;
  ClassWithCallback(this.onButtonPressed);
  ...
}

If you want to apply a name to the callback then you could use:

ClassWithCallback({@required this.onButtonPressed});

Then within that widget just call the callback whenever the button is pressed or files selected, etc?

If you need to pass data back you can use a typedef.