title: font-family "ionicons" is not a system font and has not been loaded through Font.loadAsync
body: <p>I am using native-base UI framework for react-native.  I am having same error again and again even I'm not using 'Ionicons' anywhere in my project.   I tried to delete node_modules and running <code>npm install</code> but it didn't work.<br>
  I also tried example solution given by native-base team, on github <a href="https://github.com/GeekyAnts/NativeBase-KitchenSink" rel="nofollow noreferrer">here</a>. And also solution by Expo 
  on <a href="https://docs.expo.io/versions/latest/guides/using-custom-fonts/" rel="nofollow noreferrer">Using custom fonts - Expo</a>.  <a href="https://i.stack.imgur.com/NZzhg.png" rel="nofollow noreferrer">enter image description here</a> 
  But nothing worked for me.<br>
  After trying different things it turned out that custom fonts used by native-base are not being loaded.  I've tried to load it through <code>Font.loadAsync</code> but it is not working.  </p>
  
  <pre class="lang-js prettyprint-override"><code>import * as Font from 'expo-font';
  import { AppLoading } from 'expo';
  import React, { Component } from 'react';
  import App from '../App.js';
  
  const roboto = require('../../assets/fonts/Roboto.ttf');
  const robotoMedium = require('../../assets/fonts/Roboto_medium.ttf');
  const ionicons = require('../../assets/fonts/Ionicons.ttf');
  
  export default class Setup extends Component {
    constructor() {
      super();
      this.state = {
        isReady: false,
      };
    }
  
    componentWillMount() {
      this.loadFonts();
    }
  
    async loadFonts() {
      try {
        await Font.loadAsync({
          Roboto: roboto,
          Roboto_medium: robotoMedium,
          Ionicons: ionicons,
        });
        this.setState({ isReady: true });
      } catch (e) {
        console.log(e);
      }
    }
  
    render() {
      if (!this.state.isReady) {
        return &lt;AppLoading /&gt;;
      }
      return &lt;App /&gt;;
    }
  }
  </code></pre>