由于天生一个完备的App代码涉及到许多细节和平台特定的开发（如iOS的Swift/ ...

• iOS (Swift)gzrrgx.com
  Swift:
  

swift
import UIKit
class ViewController: UIViewController {

1. override func viewDidLoad() {  
2.     super.viewDidLoad()  
3.     // Do any additional setup after loading the view.  
4.     let label = UILabel()  
5.     label.text = "Hello, World!"  
6.     label.frame = CGRect(x: 50, y: 100, width: 200, height: 50)  
7.     self.view.addSubview(label)  
8. }  

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}
2. Android (Java)
Java:
java
import android.os.Bundle;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;
public class MainActivity extends AppCompatActivity {

1. @Override  
2. protected void onCreate(Bundle savedInstanceState) {  
3.     super.onCreate(savedInstanceState);  
4.     setContentView(R.layout.activity_main);  
6.     TextView textView = new TextView(this);  
7.     textView.setText("Hello, World!");  
8.     textView.setLayoutParams(new ViewGroup.LayoutParams(  
9.             ViewGroup.LayoutParams.WRAP_CONTENT,  
10.             ViewGroup.LayoutParams.WRAP_CONTENT));  
12.     // Assuming you have a layout container with ID 'container'  
13.     ViewGroup container = (ViewGroup) findViewById(R.id.container);  
14.     container.addView(textView);  
15. }  

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}
注意：这只是一个简单的示例，通常你会在XML布局文件中界说你的UI元素。

• 跨平台 (React Native)
  React Native:
  

jsx
import React from ‘react’;
import { View, Text, StyleSheet } from ‘react-native’;
const App = () => {
return (

     Hello, World!  

);
};
const styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: ‘center’,
alignItems: ‘center’,
},
});
export default App;
4. 跨平台 (Flutter)
Flutter (Dart):
dart
import ‘package:flutter/material.dart’;
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: ‘Flutter Demo’,
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: ‘Flutter Demo Home Page’),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key? key, required this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Text(‘Hello, World!’),
),
);
}
}
这些示例只是为了展示怎样在每种平台上显示一个简单的“Hello, World!”消息。开发一个完备的App需要更多的代码和思量许多其他因素，如导航、状态管理、数据存储等。由于天生一个完备的App代码涉及到许多细节和平台特定的开发（如iOS的Swift/Objective-C，Android的Java/Kotlin，以及跨平台的React Native、Flutter等），我将为你提供每个平台或技术的简单“Hello, World!”示例。

• iOS (Swift)
  Swift:
  

swift
import UIKit
class ViewController: UIViewController {

1. override func viewDidLoad() {  
2.     super.viewDidLoad()  
3.     // Do any additional setup after loading the view.  
4.     let label = UILabel()  
5.     label.text = "Hello, World!"  
6.     label.frame = CGRect(x: 50, y: 100, width: 200, height: 50)  
7.     self.view.addSubview(label)  
8. }  

复制代码

}
2. Android (Java)
Java:
java
import android.os.Bundle;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;
public class MainActivity extends AppCompatActivity {

1. @Override  
2. protected void onCreate(Bundle savedInstanceState) {  
3.     super.onCreate(savedInstanceState);  
4.     setContentView(R.layout.activity_main);  
6.     TextView textView = new TextView(this);  
7.     textView.setText("Hello, World!");  
8.     textView.setLayoutParams(new ViewGroup.LayoutParams(  
9.             ViewGroup.LayoutParams.WRAP_CONTENT,  
10.             ViewGroup.LayoutParams.WRAP_CONTENT));  
12.     // Assuming you have a layout container with ID 'container'  
13.     ViewGroup container = (ViewGroup) findViewById(R.id.container);  
14.     container.addView(textView);  
15. }  

复制代码

}
注意：这只是一个简单的示例，通常你会在XML布局文件中界说你的UI元素。

• 跨平台 (React Native)
  React Native:
  

jsx
import React from ‘react’;
import { View, Text, StyleSheet } from ‘react-native’;
const App = () => {
return (

     Hello, World!  

);
};
const styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: ‘center’,
alignItems: ‘center’,
},
});
export default App;
4. 跨平台 (Flutter)
Flutter (Dart):
dart
import ‘package:flutter/material.dart’;
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: ‘Flutter Demo’,
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: ‘Flutter Demo Home Page’),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key? key, required this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Text(‘Hello, World!’),
),
);
}
}
这些示例只是为了展示怎样在每种平台上显示一个简单的“Hello, World!”消息。开发一个完备的App需要更多的代码和思量许多其他因素，如导航、状态管理、数据存储等。

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