The widget I built in Flutter does not appear on execution

I need your help with something. I am building a calculator using Flutter for the purpose of learning, I divided the code into two sections, Output and Keypad. I am currently in the design phase, the Output has no problem but the Keypad does not appear in the output and I asked copilot and did not benefit.
this is Keypad:

import 'package:flutter/material.dart';

class Keypad extends StatefulWidget {
  const Keypad({super.key});

  @override
  State<Keypad> createState() => _KeypadState();
}

class _KeypadState extends State<Keypad> {
  @override
  Widget build(BuildContext context) {
    return Row(
      children: [
        buttonsColumn(["7", "4", "1", "."]),
        buttonsColumn(["8", "5", "2", "0"]),
        buttonsColumn(["9", "6", "3", "="], true),
        buttonFunctionsColumn(["DEL", "/", "x", "-", "+"])
      ],
    );
  }

  Expanded buttonsColumn(List<String> contents, [bool haveEquals = false]) {
    number(String n) {}
    equals() {}
    return Expanded(
        flex: 1,
        child: Container(
          color: Colors.grey[800],
          child: Column(
            children: [
              numberButton(contents[0], number),
              numberButton(contents[1], number),
              numberButton(contents[2], number),
              numberButton(contents[3], haveEquals ? equals : number),
            ],
          ),
        ));
  }

  Expanded buttonFunctionsColumn(List<String> contents) {
    operator(String o) {}
    return Expanded(
        flex: 1,
        child: Container(
          color: Colors.grey[600],
          child: Column(
            children: [
              numberButton(contents[0], operator),
              numberButton(contents[1], operator),
              numberButton(contents[2], operator),
              numberButton(contents[3], operator),
              numberButton(contents[4], operator),
            ],
          ),
        ));
  }

  Expanded numberButton(String content, Function func) {
    return Expanded(
      flex: 1,
      child: IconButton(
          onPressed: () {
            func();
          },
          icon: Text(
            content,
            style: TextStyle(fontSize: 15),
          )),
    );
  }
}

and this is home page:

import 'package:calculator1/keypad.dart';
import 'package:calculator1/output.dart';
import 'package:flutter/material.dart';

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

class MyApp extends StatefulWidget {
  const MyApp({super.key});

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(body: Column(children: [Output(), Keypad()])),
    );
  }
}

and this is the debug:

I can’t see any problem !!!