App crashes at launch with JS bundle errors
Cause: JS bundle in the system causes conflicts. Your app doesn’t appear on the device or in thevlcm list output. You see either “Requiring unknown module” or “Property __d doesn’t exist” errors.
Solution:
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Capture the device logs:
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Launch your app using one of these commands:
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If using Kepler CLI:
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If using NPM scripts in package.json:
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If using Kepler CLI:
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Monitor the log stream for error patterns:
“Requiring unknown module” error example:
“Property ‘__d’ doesn’t exist” error example:
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If you see these errors, disable the JS bundle system and rebuild your app:
The app builds successfully but isn’t visible on the device
Cause: The app is running in the background or there are UI rendering issues. Solution:-
Check which app is currently in the foreground:
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If your app is in the background, bring it to the foreground:
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Toggle between background and foreground to refresh:
The app remains invisible after bringing to foreground
Cause: Multiple apps running on Metro server or UI code errors. Only one app can use the Metro server at a time. Solution: Check for multiple running apps:- Press Ctrl+C in the terminal where the Metro server is running to close it.
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Stop the app:
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Restart the app:
- Monitor the Metro server output for errors:
- Look for issues caused by incompatible React Native packages
- The Metro server displays errors as they occur
- Fix the errors in your code:
- The Metro server automatically rebuilds the bundle after each change
- Once you fix the error, the Metro server creates a bundle
Metro server fails to start or crashes frequently
Cause: Port conflicts, corrupted cache, or system resource constraints. Solution:-
Clear Metro cache:
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Check for port conflicts and use a different port:
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Restart Metro server with verbose logging:
- If issues persist, restart your development machine to clear system resources.
