Flutter: Widget Tree

Question

There are two Widgets I created, and a main Widget. But i am getting an Error:

"package:flutter/src/rendering/proxy_box.dart': Failed assertion: line 1899"

Main Widget:

      @override
      Widget build(BuildContext context) {
        return Drawer(
          child: Column(
            children: [
              buildHeader(), 
              buildMenu()
              ],
          ),
        );
      }

First Widget:

Widget buildHeader() {
          return const Center(
            child: Card(
              child: SizedBox(
                width: 300,
                height: 100,
                child: Center(child: Text('Elevated Card')),
              ),
            ),
          );
        }

Second Widget:

     Widget buildMenu() {
       return Drawer(
           child: FutureBuilder<List<Menu>>(
         future: listMenus,
         builder: (context, snapshot) {
           if (snapshot.hasData) {
             return ListView.builder(
               itemCount: (snapshot.data as List<Menu>).length,
               itemBuilder: (context, index) {
                 var menu = (snapshot.data as List<Menu>)[index];
                 return Padding(
                   padding: const EdgeInsets.symmetric(vertical: 1, horizontal: 4),
                   child: Card(
                     child: ListTile(
                       onTap: () {
                         // print(listMenus[index]);
                       },
                       title: Text(menu.folder),
                     ),
                   ),
                 );
               },
             );
           } else if (snapshot.hasError) {
             return Center(
               child: Text("${snapshot.error}"),
             );
           }
           return const Center(
             child: CircularProgressIndicator(
               backgroundColor: Colors.cyanAccent,
             ),
           );
         },
       ));
     }

.....................................................................

Answer 1

The main widget is returning a drawer and the second widget is also returning a drawer. In second widget replace the drawer with an Expanded widget or SizedBox of specific height and width

EDIT

I checked your codes with some dummy data and getting the result as expected

import 'package:flutter/material.dart';

void main() async {
  runApp(const MyApp());
}

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(home: Center(child: DemoClass()));
  }
}

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      drawer: Drawer(
        child: Column(
          children: [
            buildHeader(),
            buildMenu(),
          ],
        ),
      ),
    );
  }
}

Widget buildHeader() {
  return const Center(
    child: Card(
      child: SizedBox(
        width: 300,
        height: 100,
        child: Center(child: Text('Elevated Card')),
      ),
    ),
  );
}

Widget buildMenu() {
  return Expanded(
      child: FutureBuilder<List<Menu>>(
        future: listMenus,
        builder: (context, snapshot) {
          if (snapshot.hasData) {
            return ListView.builder(
              itemCount: (snapshot.data as List<Menu>).length,
              itemBuilder: (context, index) {
                Menu menu = (snapshot.data as List<Menu>)[index];
                return Padding(
                  padding: const EdgeInsets.symmetric(vertical: 1, horizontal: 4),
                  child: Card(
                    child: ListTile(
                      onTap: () {
                        // print(listMenus[index]);
                      },
                      title: Text(menu.folder),
                    ),
                  ),
                );
              },
            );
          } else if (snapshot.hasError) {
            return Center(
              child: Text("${snapshot.error}"),
            );
          }
          return const Center(
            child: CircularProgressIndicator(
              backgroundColor: Colors.cyanAccent,
            ),
          );
        },
      ));
}