Call Function From Another Flutter Class

Question

I would like to call function between another clas. So when the menu tapped from grabDrawer it will change the currentIndex at Main() class. Do you know how to do that? Here is so far I have tried.

main.dart

class _MainState extends State<Main> {
  int currentIndex = 0;
  Map<String,dynamic> searchParameter = {};

  List screens = [
    Home(),
    Search({}),
  ];
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        automaticallyImplyLeading: false,
        actions: [
          Builder(builder: (context){
            return IconButton(
              onPressed: (){
                Scaffold.of(context).openEndDrawer();
              },
              icon: const Icon(Icons.menu),
            );
          }),
        ],
      ),
      endDrawer: const Drawer(
        child:DrawerObject(),
      ),
      floatingActionButton: FloatingActionButton(
        child: Icon(Icons.arrow_upward),
        onPressed: () async{
          await Future.delayed(Duration(milliseconds: 100),(){
            globals.scrollController.animateTo(0, duration: Duration(milliseconds: 500), curve: Curves.fastOutSlowIn);
          });
        },
      ),
      body: screens[currentIndex],
      bottomNavigationBar: BottomNavigationBar(
        currentIndex: currentIndex,
        onTap: (index) => setState(() {
          if (index == 1) {
            getSearchForm(context);
          } else {
            currentIndex = index;
            searchParameter = {};
          }
        }),
        selectedItemColor: Colors.white,
        unselectedItemColor: Colors.grey[100],
        type: BottomNavigationBarType.shifting,
        items: [
          BottomNavigationBarItem(
            icon: Icon(Icons.home),
            label: 'Home',
            backgroundColor: Colors.blue[500],
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.search),
            label: 'Pencarian',
            backgroundColor: Colors.orange[500],
          ),
        ],
      ),
    );
  }

  //main function ===> NEED TO CALL THIS FUNCTION INSIDE grabDrawer.dart
  Future UpdateIndex({int Index = 0}) async{
    setState(() {
      currentIndex = Index;
    });
  }

  Future getSearchForm(BuildContext context) async {
    final result = await Navigator.push(
      context,
      MaterialPageRoute(builder: (context) => SearchForm(parameter:searchParameter)),
    );

    setState(() {
      if (result != null) {
        currentIndex = 1;
        if(result!=searchParameter){
          searchParameter = result;
          screens[1] = CallLoading(show: ''); //set default to load
          //set to new parameter (rebuilding widget)
          Future.delayed(Duration(milliseconds: 500),(){
            setState(() {
              screens[1] = Search(searchParameter);
            });
          });
        }
      }
      else{
      }
    });
  }
}

Under this file, I need to call function from Main.UpdateIndex.

grabDrawer.dart

class DrawerObject extends StatelessWidget {
  const DrawerObject({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Container(
      child: ListView(
        children: [
          ListTile(
              leading: Icon(Icons.home),
              title: Text('Cari Properti?'),
              onTap: (){
===> CALL IT HERE
              }
          ),
        ],
      ),
    );
  }
}

I really appreciate any answers. Thank you.

check out this link to get some hint: https://stackoverflow.com/a/52550939/11404883 — Aamil Silawat, Apr 05 '22 at 04:47
Hi, it comes from parent looks like a callback. However, I does not work when implementing from Stateful widget. Please check my code. — Roohome Com, Apr 05 '22 at 05:13

score 2 · Answer 1 · answered Apr 05 '22 at 05:18

Change your grabDrawer.dart like this

class DrawerObject extends StatelessWidget {
  void Function()? UpdateIndex;

   DrawerObject({
    this.UpdateIndex,
  });

@override
  Widget build(BuildContext context) {
    return Container(
       child: ListView(
          children: [
               ListTile(
               leading: Icon(Icons.home),
               title: Text('Cari Properti?'),
               onTap: (){
                UpdateIndex!();
             }
          ),
        ],
      ),
    );
  }
}

And in your main.dart, call Drawer class like this

endDrawer: const Drawer(
    child:DrawerObject(
        UpdateIndex: UpdateIndex,
      );
  ),

Hope this works for you.

score 1 · Accepted Answer · answered Apr 05 '22 at 06:46

Here is the clear way to pass data between one class to another class

  void main() {
      runApp(MaterialApp(
        home: Modalbtn(),
      ));
    }

    class Modalbtn extends StatefulWidget {
      @override
      _ModalbtnState createState() => _ModalbtnState();
    }
    
    class _ModalbtnState extends State<Modalbtn> {
      String value = "0";
      // Pass this method to the child page.
      void _update(String newValue) {
        setState(() => value = newValue);
      }
    
      @override
      Widget build(BuildContext context) {
        return Scaffold(
          body: SafeArea(
            child: Column(
              children: [
                IconButton(
                  onPressed: () {
                    showModalBottomSheet(
                        context: context,
                        builder: (BuildContext context) {
                          return Container(
                            height: 200,
                            child: Column(
                              children: [StatefulModalbtn(update: _update)],
                            ),
                          );
                        });
                  },
                  icon: Icon(Icons.add),
                  iconSize: 20,
                ),
                Text(
                  value,
                  style: TextStyle(fontSize: 40),
                ),
              ],
            ),
          ),
        );
      }
    }
    
    import 'package:flutter/material.dart';
    
    class StatefulModalbtn extends StatelessWidget {
      final ValueChanged<String> update;
      StatefulModalbtn({required this.update});
    
      @override
      Widget build(BuildContext context) {
        return ElevatedButton(
          onPressed: () => update("100"), // Passing value to the parent widget.
    
          child: Text('Update (in child)'),
        );
      }
    }

Call Function From Another Flutter Class

2 Answers2