How could I update inner widget if list changes, and notify outer widget if inner widget changes?-CodePudding

I basically have a structure like this:

--OuterWidget
  --ListWidget
    --ListElementWidget1
    --ListElementWidget2
    ...
    --ListElementWidget3

WHat I wanna do is the following: whenever a user checks a checkbox in ListElementWidget, I want to be notified about that in OuterWidget. Also, whenever I add an element to the list in OuterWidget, I want that to be reflected in ListWidget. I could do the simple method of passing down a notifier in constructor, but is there a simpler way?

CodePudding user response：

Welcome to the world of State Management!

The easiest way to know if a checkbox changed in ListElementWidget is passing a callback method down the chain, like you've already mentioned, then calling that when the user checks a checkbox.

OuterWidget() => ListWidget(toggleCheckCallBack) => ListElementWidget(toggleCheckCallBack);

And, for the updating of the ListWidget, simply making OuterWidget a StatefulWidget and calling setState when an element is added should resolve that too.

While this does solve the issue, it probably wouldn't scale well, if you believe this is a problem, take a look at the various state management libraries Flutter has.

CodePudding user response：

Look at stateful widgets

void onPressed() {
  setState(() {
    // Here you can set values in your widget 
    // and it will update all widgets in state.
  });
}

Sorry if code wrong I am typing from memory... Full code example:

class Page extends StatefulWidget {
  @override
  State createState(BuildContext context) => _PageState();
}

class _PageState extends State<Page> {
  int someValue = 0; 

  Widget build() => TextButton(
    text: Text(someValue.toString()),
    onPress: () => SetState(() {
      someValue  = 4;
    })
  )
}