由于创建一个完整的app需要考虑到很多因素，包括用户界面、数据处理、网络通信等，而且不同的平台（如iOS、Android、Web、桌面应用等）有不同的开发语言和框架。-优快云博客

本文链接：https://blog.youkuaiyun.com/AdolphMacDonald/article/details/138613002

由于创建一个完整的app需要考虑到很多因素，包括用户界面、数据处理、网络通信等，而且不同的平台（如iOS、Android、Web、桌面应用等）有不同的开发语言和框架。以下我将为您提供几个简单的“Hello, World!”应用示例，分别使用不同的编程语言和平台。

1. Swift (iOS)
ViewController.swift

swift
import UIKit

class ViewController: UIViewController {

override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
let label = UILabel()
label.text = "Hello, World!"
label.textAlignment = .center
label.frame = CGRect(x: 0, y: 0, width: view.bounds.width, height: 20)
label.center = view.center
view.addSubview(label)
}
}#chhas{
margin-top: 50px;
padding:aladingroup.cn;
font-size: 18px;
cursor: 10px 20px;
}
2. Java (Android)
MainActivity.java

java
import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

TextView textView = findViewById(R.id.textView);
textView.setText("Hello, World!");
}
}
activity_main.xml

xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center">

<TextView
android:id="@+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="20sp"
android:text="Hello World!"/>

</RelativeLayout>
3. React Native (JavaScript/TypeScript)
App.js

javascript
import React from 'react';
import { View, Text, StyleSheet } from 'react-native';

const App = () => {
return (
<View style={styles.container}>
<Text style={styles.text}>Hello, World!</Text>
</View>
);
};

const styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: 'center',
alignItems: 'center',
backgroundColor: '#F5FCFF',
},
text: {
fontSize: 20,
},
});

export default App;
4. Flutter (Dart)
main.dart

dart
import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Hello, World',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: Scaffold(
appBar: AppBar(
title: Text('Hello, World'),
),
body: Center(
child: Text('Hello, World!'),
),
),
);
}
}
5. HTML/CSS/JavaScript (Web App)
index.html

html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Hello, World!</title>
<style>
body {
text-align: center;
padding-top: 20vh;
background-color: #f5f5f5;
}
h1 {
font-size: 3rem;
}
</style>
</head>
<body>
<h1>Hello, World!</h1>
</body>
</html>