index.js

/**
 * @format
 */
import { AppRegistry } from 'react-native';
import App from './App';
import { name as appName } from './app.json';
import { gestureHandlerRootHOC } from 'react-native-gesture-handler'

import notifee, { AndroidImportance } from '@notifee/react-native'
import messaging from '@react-native-firebase/messaging'

//background & quit state: messages listener   
async function onBackgroundMessageReceived(message) {

    const channelId = await notifee.createChannel({
        id: 'projects',
        name: 'projects',
        lights: false,
        vibration: true,
        importance: AndroidImportance.HIGH,
    })

    await notifee.displayNotification(JSON.parse(message.data.notifee))
}

messaging().setBackgroundMessageHandler(onBackgroundMessageReceived)

AppRegistry.registerComponent(appName, () => gestureHandlerRootHOC(App));