React Native条码示例应用执行run-android后出现503错误求助

Hey there, I know how frustrating it is to get your app installed only to hit a 503 error. Let's walk through some practical fixes that should get your barcode sample app up and running:

1. Make Sure Metro Server is Running Properly #

Sometimes the Metro bundler doesn't start correctly when you run react-native run-android. Try this:

• Open a new terminal window, navigate to your project root, and run:

  npx react-native start
  

• Wait until you see the "Metro waiting on..." message, then go back to your original terminal and re-run react-native run-android.

2. Clear All Caches (A Common Culprit) #

Cached data can often cause unexpected server errors. Run these commands one by one:

• Reset React Native's cache:

  npx react-native start --reset-cache
  

• Clean your Android project's build files:

  cd android && ./gradlew clean && cd ..
  

Then try building and running the app again.

3. Verify Device-Metro Connectivity #

Your app needs to reach the Metro server on your computer. Here's how to fix connection issues:

• For physical devices: Ensure USB debugging is enabled, then run this command to forward ports:

  adb reverse tcp:8081 tcp:8081
  

• For emulators/physical devices: Open the React Native dev menu (Ctrl+M for emulators, shake your device for physical ones), select "Change Bundle Location", and enter your computer's local IP plus port 8081 (e.g., http://192.168.1.5:8081/index.bundle).
• Double-check that your device and computer are on the same Wi-Fi network.

4. Check for Port Conflicts #

Metro uses port 8081 by default—if another app is using it, you'll get a 503 error:

• Windows: Find the process using 8081:

  netstat -ano | findstr :8081
  

  Kill it with:

  taskkill /PID <ProcessID> /F
  

• Mac/Linux: Find the process:

  lsof -i :8081
  

  Kill it with:

  kill -9 <ProcessID>
  

Restart Metro after this.

5. Validate Dependencies & Permissions #

• Double-check that your barcode-related libraries (like react-native-camera or similar) are installed correctly and compatible with your React Native version.
• Ensure your android/app/src/main/AndroidManifest.xml includes the internet permission—this is required for the app to connect to Metro:

  <uses-permission android:name="android.permission.INTERNET" />
  

If none of these steps work, try restarting your computer and device—sometimes a fresh start fixes weird connectivity glitches.

内容的提问来源于stack exchange，提问作者Rashiq