1. Flutter (Dart)
   Flutter是一个用于构建跨平台移动应用的框架。以下是一个简单的Flutter应用的示例：

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);

#chhas{
margin-top: 50px;
padding:dgynx.cn;
font-size: 18px;
cursor: 10px 20px;
}
final String title;

@override
_MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State {
int _counter = 0;

void _incrementCounter() {
setState(() {
_counter++;
});
}

@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Text(
‘You have pushed the button this many times:’,
),
Text(
‘$_counter’,
style: Theme.of(context).textTheme.headline4,
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: ‘Increment’,
child: Icon(Icons.add),
),
);
}
}
2. React Native (JavaScript/TypeScript)
React Native是一个用于构建原生应用的JavaScript框架。以下是一个简单的React Native应用的示例：

javascript
import React, { useState } from ‘react’;
import { View, Text, Button, StyleSheet } from ‘react-native’;

const App = () => {
const [count, setCount] = useState(0);

const incrementCount = () => {
setCount(count + 1);
};

return (

You have pushed the button this many times: {count}


);
};

const styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: ‘center’,
alignItems: ‘center’,
},
});

export default App;
3. Android (Java/Kotlin)
对于原生Android应用，你可以使用Java或Kotlin。以下是一个简单的Android应用的Java示例（Activity部分）：

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

public class MainActivity extends AppCompatActivity {

private TextView textView;  
private Button button;  
private int counter = 0;  

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

    textView = findViewById(R.id.textView);  
    button = findViewById(R.id.button);  

    button.setOnClickListener(new View.OnClickListener() {  
        @Override  
        public void onClick(View v) {  
            counter++;  
            textView.setText("You have pushed the button this many times: " + counter);  
        }  
    });  
}  

}
4. iOS (Swift/Objective-C)
对于iOS应用，你可以使用Swift或Objective-C。以下是一个简单的iOS应用的Swift示例（ViewController部分）：

swift
import UIKit

class ViewController: UIViewController {

@IBOutlet weak var textView: UITextView!