Use Flutter on Ubuntu

How to install Flutter on Ubuntu 20.10 and use it as a web server.

Installation of prerequisite software

sudo apt install clang curl pkg-config ninja-build cmake libblkid-dev libgtk-3-dev

Install Flutter

git clone https://github.com/flutter/flutter.git

Go to/usr/local/flutter

Set path

export PATH=$PATH:/usr/local/flutter/bin

Confirmation of installation

$ flutter doctor
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel master, 1.26.0-2.0.pre.220, on Linux, locale ja_JP.UTF-8)
[!] Android toolchain - develop for Android devices (Android SDK version 27.0.1)
    ✗ Flutter requires Android SDK 29 and the Android BuildTools 28.0.3
      To update the Android SDK visit
      https://flutter.dev/docs/get-started/install/linux#android-setup for
      detailed instructions.
    ✗ Android license status unknown.
      Run `flutter doctor --android-licenses` to accept the SDK licenses.
      See https://flutter.dev/docs/get-started/install/linux#android-setup for
      more details.
[✓] Chrome - develop for the web
[✓] Linux toolchain - develop for Linux desktop
[!] Android Studio (not installed)
[✓] Connected device (2 available)

! Doctor found issues in 2 categories.

Software creation

flutter create myapp
cd myapp

Run as a web server (ports will be random)

$ flutter run -d web-server
Launching lib/main.dart on Web Server in debug mode...
Waiting for connection from debug service on Web Server...         25.3s
lib/main.dart is being served at http://localhost:42819

In the browser http://localhost:42819 To access

To start by specifying a port

flutter run -d web-server --web-port=1234

Modify the program. Replace lib/main.dart with:

lib/main.dart

import 'package:flutter/material.dart';

void main() {
  runApp(ExampleApp());
}

class ExampleApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: HelloWorld(),
    );
  }
}

class HelloWorld extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
String str_out = 'Hello.\n';
str_out += 'It's sunny today.\n';
str_out += 'Jan/08/2021\n';
    return Scaffold(
      appBar: AppBar(
        title: Text('Flutter Example App'),
      ),
      body: Container(
        alignment: Alignment.center,
        child: Text(
          str_out,
          style: TextStyle(
            fontSize: 70,
            fontWeight: FontWeight.bold,
          )
        ),
      )
    );
  }
}

Start the server and access from the browser