Application main has not been registered

Question

I have recently started to convert my react native app and running on Expo so i could test this on my actual android device. I am getting this error above. I have since then running my app using the Expo XDE. I am also running on a windows machine.

The full error message is:

enter image description here ]1

I figured that this has something to do with my index.js, yet here it is

import { AppRegistry } from 'react-native';
import App from './App';

AppRegistry.registerComponent('projectTARA', () => 'App');

and no i did change the name of my project. my root folder is called projectTARA @Rafael Motta — johnobc, Mar 21 '18 at 22:20
solved the issue i had to change AppRegistry.registerComponent('main', => App); — johnobc, Mar 21 '18 at 22:28
wow changing the registerComponent to 'main' instead of the name of my project 'AwesomeProject' worked, but I've not seen this documented anywhere, quite the opposite, I see everyone else say to use the name of your app here. Thank You @johnobc!!! — Brandon Culley, Apr 11 '18 at 01:37

score 23 · Accepted Answer · answered Mar 27 '19 at 22:54

23

The following solution worked:

AppRegistry.registerComponent('main',() => App);

Credits: Rishav Kumar

(Cannot you people just reply to mark as solve ?)

answered Mar 27 '19 at 22:54

ATX

1,139
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Well though this may help, the reason depends on how is "index.android" or "index.ios" in native code. For example in android case last answer here could help https://stackoverflow.com/questions/38340360/react-native-application-has-not-been-registered-error/57336321#57336321 – Carmine Tambascia Aug 03 '19 at 08:51
2

Is this supposed to be typed at the command prompt or placed in a file? – kojow7 Aug 14 '19 at 07:25

score 2 · Answer 2 · answered Jun 26 '18 at 09:47

2

The problem is you haven't opened your project in Android Studio. The previous project is running in android studio and you are running the latest one in emulator.

answered Jun 26 '18 at 09:47

Sushmitha Samudrala

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2

5

**AppRegistry.registerComponent('main',() => App);** This is how the error was solved – Rishav Kumar Oct 29 '18 at 07:19
@RishavKumar without any import from app.json ? – DevAS Jan 23 '19 at 22:52
@Gha app.json? What does it has to do ? – Rishav Kumar Jan 24 '19 at 08:46
Try this one : import { AppRegistry } from 'react-native'; import App from './App'; AppRegistry.registerComponent('main',() => App); – Rishav Kumar Jan 24 '19 at 08:46

score 2 · Answer 3 · edited Apr 17 '19 at 09:58

I created a Project from "Doco", and save it with Practice. so write that line like that

AppRegistry.registerComponent('Practice', () => FixedDimensionsBasics);

then I get an error like in a question

So, I check on my Appdelegate.m file on ios folder and find that Project name is Project so I change that line with

AppRegistry.registerComponent('Project', () => FixedDimensionsBasics);

and my Error solved

so if you are using "Doco" then check that thing.

score 1 · Answer 4 · answered Aug 14 '19 at 07:38

I came across this issue because I had previously run a React project that was not fully shut down. To fix this, I could have restarted my computer. But I chose to do this instead: (Using MacOS, should work with Linux as well, for Windows you would likely need to use Task Manager or similar):

Open terminal
Find the program that is using port 8081 by typing "lsof -i :8081". (Note this is LSOF in lowercase)
Look at the process ID (under the PID column)
Kill the process by typing "kill -9 PID" (where PID is the process ID number you found in step 3).

After killing the process you should be able to run your react-native project.

score 1 · Answer 5 · answered Aug 30 '20 at 10:18

1

Removed node_modules and reinstalled by yarn that worked for me.

answered Aug 30 '20 at 10:18

tiennv

356
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3

this happened to me because I globally updated expo but the project was generated with an older version, so your solution did the trick – Daniel Arechiga Sep 06 '20 at 06:51

score 0 · Answer 6 · answered Mar 11 '22 at 20:34

Error ? if you are running your app on the expo framework, the framework cannot find registration of the main App,or its entry point.

Solution ? go to you entry script, could be "src/main.js" or in my case the "App.js" then;

import { registerRootComponent } from 'expo';

export default function App(){
    //your code app code goes here
}

registerRootComponent(App);

Refer here: https://docs.expo.dev/versions/latest/sdk/register-root-component/

Application main has not been registered

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