Read nested widget/class properties value in flutter-CodePudding

I'm building a simple app with lots of nested widgets/classes from different specialised files

list of files:

main.dart -> the menu file used to start the activity "Activity()"

group_widgets.dart -> the file that contains the custom widget "CustomWidget()"

file_a.dart -> the file that uses the custom widgets inside the "Activity()"

other.dart -> other files that needs to manage data changed in CustomWidget()

inside main.dart:

onPressed: () {
 Navigator.push(
  context,
  MaterialPageRoute(
   builder: (context) => const Activity(),
 ));
},

inside group_widgets.dart:

class CustomWidget extends StatefulWidget {
  const CustomWidget({Key? key}) : super(key: key);

  @override
  State<CustomWidget> createState() => _CustomWidgetState();
}

class _CustomWidgetState extends State<CustomWidget> {
  var _boolean = false;
  bool switchBoolean(bool state) => !state;

  @override
  Widget build(BuildContext context) {
    return ElevatedButton(
      onPressed: () => {
        setState(() {
          _boolean = switchBoolean(_boolean);
        })
      },
      child: Container(
        color: _boolean == true ? Colors.green : Colors.red,
      ),
    );
  }
}

inside file_a.dart

class Activity extends StatefulWidget {
  const Activity({Key? key}) : super(key: key);

  @override
  State<Activity> createState() => _ActivityState();
}

class _ActivityState extends State<Activity> {
  @override
  Widget build(BuildContext context) {

    bool boolean = true;

    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: const [
            CustomWidget(),
            Text('Here where to show the variable from CustomWidget'
                'and prove I can retrieve it')
          ],
        ),
      ),
    );
  }
}

inside other.dart

if ( booleanFromCustomWidget == true) {
  Something ...
}

What is the best practice to achieve it? I've read a lot here but nothing seems to well fit my needing.

Just comment if my request is not as clear as it seems to me))

CodePudding user response：

Please correct me if I am wrong, but if you want to access data from parent widgets from inside their descendants (children or even nested children) you can either pass them down via parameter arguments:

 Child(int age, String name);

And then accept it in the new file, where the Child widget lives, via its constructor:

class Child{
  String name;
  int age;
     
  // Constructor
  Child(String passedName, int passedAge) {
    this.name = passedName;
    this.age = passedAge;
   
  }
}

Inside the parent.dart you then have to import the children.dart to use it.

Or use a popular package like the provider package: https://pub.dev/packages/provider This allows you to store data containers, which you can access basically anywhere in your code. Feel free to google it & watch some tutorials to get started, as it is the preffered approach to avoid passing data to widget which really do not care about the passed parameters.

Note: You can transfer the idea to output the String data like in your example code above.

CodePudding user response：

you can use a state manager like provider, or bloc At the top level, you set up the data services