App.js

import React from 'react';
import { StyleSheet, View, ActivityIndicator } from 'react-native';
import { Font } from 'expo';
import Text from './components/CustomText';
export default class App extends React.Component {
  constructor() {
    super();
    this.state = {
      fontLoaded: false
    };
  }

  async componentDidMount() {
    await Font.loadAsync({
      'Raleway-Black': require('./assets/fonts/Raleway-Black.ttf'),
      'Raleway-Bold': require('./assets/fonts/Raleway-Bold.ttf'),
      'Raleway-SemiBold': require('./assets/fonts/Raleway-SemiBold.ttf'),
      'Raleway-Medium': require('./assets/fonts/Raleway-Medium.ttf'),
      'Raleway-Regular': require('./assets/fonts/Raleway-Regular.ttf')
    });

    this.setState({ fontLoaded: true });
  }
  render() {
    return (
      <View style={styles.container}>
        {this.state.fontLoaded ? (
          <Text type="bold">Open up App.js to start working on your app!</Text>
        ) : (
          <ActivityIndicator size="large" />
        )}
      </View>
    );
  }
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#fff',
    alignItems: 'center',
    justifyContent: 'center'
  }
});