How to detect first launch in react-native

I made some adjustments to martinarroyo's suggestion. AsyncStorage.setItem should set a string value and not a bool.

import { AsyncStorage } from 'react-native';
    
const HAS_LAUNCHED = 'hasLaunched';

function setAppLaunched() {
  AsyncStorage.setItem(HAS_LAUNCHED, 'true');
}

export default async function checkIfFirstLaunch() {
  try {
    const hasLaunched = await AsyncStorage.getItem(HAS_LAUNCHED);
    if (hasLaunched === null) {
      setAppLaunched();
      return true;
    }
    return false;
  } catch (error) {
    return false;
  }
}

This function can then be imported wherever you need it. Note that you should render null (or something else clever) while waiting for the async function to check AsyncStorage.

import React from 'react';
import { Text } from 'react-native';
import checkIfFirstLaunch from './utils/checkIfFirstLaunch';

export default class App extends React.Component {
  constructor(props) {
    super(props);

    this.state = {
      isFirstLaunch: false,
      hasCheckedAsyncStorage: false,
    };
  }

  async componentWillMount() {
    const isFirstLaunch = await checkIfFirstLaunch();
    this.setState({ isFirstLaunch, hasCheckedAsyncStorage: true });
  }

  render() {
    const { hasCheckedAsyncStorage, isFirstLaunch } = this.state;

    if (!hasCheckedAsyncStorage) {
      return null;
    }

    return isFirstLaunch ?
      <Text>This is the first launch</Text> :
      <Text>Has launched before</Text>
    ;
  }
}

Your logic should follow this:

class MyStartingComponent extends React.Component {
    constructor(){
        super();
        this.state = {firstLaunch: null};
    }
    componentDidMount(){
        AsyncStorage.getItem("alreadyLaunched").then(value => {
            if(value == null){
                 AsyncStorage.setItem('alreadyLaunched', true); // No need to wait for `setItem` to finish, although you might want to handle errors
                 this.setState({firstLaunch: true});
            }
            else{
                 this.setState({firstLaunch: false});
            }}) // Add some error handling, also you can simply do this.setState({fistLaunch: value == null})
    }
    render(){
       if(this.state.firstLaunch === null){
           return null; // This is the 'tricky' part: The query to AsyncStorage is not finished, but we have to present something to the user. Null will just render nothing, so you can also put a placeholder of some sort, but effectively the interval between the first mount and AsyncStorage retrieving your data won't be noticeable to the user.
       }else if(this.state.firstLaunch == true){
           return <FirstLaunchComponent/>
       }else{
           return <NotFirstLaunchComponent/>
       }
}

Hope it helps