我正在使用React Native Expo与Android，React和Express作为API。
当我访问API的地址时，我会收到一条消息。当我从React中获取它时，我会收到一条消息。当我尝试从React Native中获取时，我在控制台中得到“Error fetching data：[TypeError：Network request failed]”，而JS调试器中什么都没有。
我已经尝试了多个端口的所有来源和axios。我已经改变了特定端口的cors，重新启动一切多次，检查权限。
这里是我做的测试应用程序-我每次都得到相同的结果。谢谢！
表达

const express = require('express');
const cors = require('cors'); // Import the cors middleware
const app = express();
const port = 4321;

// Use the cors middleware
app.use(cors());

app.get('/', (req, res) => {
  res.send({message: 'Hello'});
});

app.listen(port, () => {
  console.log(`Server is running on http://localhost:${port}`);
});

字符串
React Native

import React, { useEffect } from 'react';

const App = () => {
  useEffect(() => {
    const fetchData = async () => {
      try {
        const response = await fetch('http://localhost:4321');
        if (!response.ok) {
          throw new Error('Network response was not ok');
        }

        const data = await response.json();
        console.log('Data from the server:', data);
      } catch (error) {
        console.error('Error fetching data:', error);
      }
    };

    fetchData();
  }, []);

  return (
    <></>
  );
};

export default App;

型
React（与RN相同）

import React, { useEffect } from 'react';

const App = () => {
  useEffect(() => {
    const fetchData = async () => {
      try {
        const response = await fetch('http://localhost:4321');
        if (!response.ok) {
          throw new Error('Network response was not ok');
        }

        const data = await response.json();
        console.log('Data from the server:', data);
      } catch (error) {
        console.error('Error fetching data:', error);
      }
    };

    fetchData();
  }, []);

  return (
    <></>
  );
};

export default App;

型