register-listener.js

class App extends React.Component {
  state = {
    notification: ""
  };
    
  registerForPushNotificationsAsync = async () => {
    // Same as earlier
  }
  
  handleNotification = notification => {
    this.setState({ notification });
  }
  
  componentDidMount() {
    this.registerForPushNotificationsAsync();
    
    this.notificationSubscription = Notifications.addListener(this.handleNotification);
  }
  
  render() {
    // Display the notification in the view
  }
};