react-native: Invariant Violation: "app" has not been registered - AppRegistry.js | runnables[appKey] is undefined

Can you please share the contents of the index.js file at the root of the project?

The error usually points to the code below which is found at <root folder>/index.js. Also from version did you upgrade?

// index.js
import {AppRegistry} from 'react-native';
import App from './App';
import {name as appName} from './app.json';

AppRegistry.registerComponent(appName, () => App); // <- this line

in my case, there were 2 files left from the previous developer and for a long time I could not understand the cause of the error Here we have App.js and index.js

with this code in index.js

// This is the first file that ReactNative will run when it starts up.
// If you use Expo (`yarn expo:start`), the entry point is ./App.js instead.
// Both do essentially the same thing.

import App from "./app/app.tsx"
import React from "react"
import { AppRegistry } from "react-native"
import RNBootSplash from "react-native-bootsplash"

function IgniteApp() {
  return <App hideSplashScreen={RNBootSplash.hide} />
}

AppRegistry.registerComponent("main", () => IgniteApp)
export default App

and code in App.js

import App from "./app/app.tsx"
import React from "react"
import { registerRootComponent } from "expo"
import { Platform } from "react-native"
import * as SplashScreen from "expo-splash-screen"

SplashScreen.preventAutoHideAsync()

function IgniteApp() {
  return <App hideSplashScreen={SplashScreen.hideAsync} />
}

if (Platform.OS !== "web") {
  registerRootComponent(IgniteApp)
}

export default IgniteApp

when a build is created, expo refers to App.js and does not see the AppRegistry.registerComponent there, to solve the problem, it is enough to replace all the code in App.js with the code from Index.js and everything will work

I still facing this issue while upgraded to react native 0.71.4 from 0.64 any solution for this issue I tried lots of solutions which are

1. Matched project name in app.json
2. also ensure in MainActivity getMainComponentName has match with app.json
3. also ensure metro bundler running from proper folder
4. also ensure previous app is deleted from mobile
5. also ensure project file name was match with app.json and MainActivity names

index.js file

 import 'react-native-gesture-handler';
 import {AppRegistry, LogBox} from 'react-native';
 import {name as appName} from './app.json';
 import App from "./App"
 AppRegistry.registerComponent(appName, () => App);

app.json file

{
   "name": "appname",
   "displayName": "displayName",
   "react-native-google-mobile-ads": {
   "android_app_id": "key"
  }
}

MainActivity.java file ensuring match with app.json with this file

  @Override
    protected String getMainComponentName() {
        return "appname";
    }

Please any solution for reply this

This issue was cleared successfully. So anyone wants to resolve this make sure the below points are cleared

1. First match In app.json name as the same name in MainActivity.java return value of getMainComponentName
2. Second try to debug code by commenting in the entry(which is index.js or App.js) file check this where is exactly the main problem My problem was I updated the app and all required packages but one function was deprecated in redux which is createStore by solving this resolved my issue

@DaraUkpong It absolutely worked. Shall we raise an issue in ignite boilerplate? If I didn’t come across your comment I would have never figured it out. How did you manage to find it?

I had to take a close look of where the app was actually reading it’s entry point from using the Android Studio logging tool. On both builds it read from app.js or index.js(release and dev build). I just had to make sure both had the same content.

At the time I just needed a solution the problem, I haven’t researched as to why that was happening given that I had no prior interaction with those files.

An Issue - Yes that will work. I’ve not tried the new update to confirm if it’s something that has been resolved. You trying to solve this issue at this time means it probably hasn’t.

@vikil143 Tried debugging the issue, Understood that the issue is due to the ‘require’ statements in the js files. The error is thrown wherever export/import is used in tsx files ie; require in compiled js files. Trying to resolve it.

This error also caused when you running metro bundler of different project is not closed. So try to kill all metro bundlers as well as restart your PC check once

What else have you tried to fix this error?

Side note: https://github.com/facebook/react-native/commit/57774a4a981e2f12cfe9b029447e34f203221b18

./app.json

{
  "name": "AwesomeApp",
  "displayName": "AwesomeApp"
}

@TomJerry56 What was cause this issue appear?

Upgradation of react-native to 0.71, react to 18, gradle, node and its respective dependencies

Can you send some more details like what are trying to do and what you did? and My suggestion is debug the code properly then you can get where is actual bug