App.js

import Expo from "expo";
import React from "react";
import App from "./js/AppMain";

export default class App1 extends React.Component {
    constructor() {
        super();
        this.state = {
        isReady: false
        };
    }
    
    async componentWillMount() {
        await Expo.Font.loadAsync({
                                  Roboto: require("native-base/Fonts/Roboto.ttf"),
                                  Roboto_medium: require("native-base/Fonts/Roboto_medium.ttf"),
                                  Ionicons: require("@expo/vector-icons/fonts/Ionicons.ttf")
                                  });
        
        this.setState({ isReady: true });
    }
    render() {
        if (!this.state.isReady) {
            return <Expo.AppLoading />;
        }
        return <App />;
    }
}