How to load custom fonts using hook useFonts in Storybook and React Native?

When using Storybook to showcase components in a React Native project, it is essential to ensure that components display correctly across various scenarios, including the proper loading and rendering of custom fonts. React Native provides a hook named useFonts that can load custom fonts within components. Below is a detailed guide on integrating useFonts with Storybook for loading custom fonts.

Step 1: Install the necessary libraries

First, ensure you have installed the expo-font library, as the useFonts hook is provided by it. If not installed, you can install it using the following command:

bash
npm install expo-font

Step 2: Use useFonts to load fonts

In your React Native component, you can use useFonts to asynchronously load fonts. Here's a simple example:

javascript
import React from 'react';
import { Text, View } from 'react-native';
import { useFonts } from 'expo-font';

const CustomFontComponent = () => {
  let [fontsLoaded] = useFonts({
    'CustomFont': require('./assets/fonts/CustomFont.ttf'),
  });

  if (!fontsLoaded) {
    return <View><Text>Loading...</Text></View>;
  } else {
    return <View><Text style={{ fontFamily: 'CustomFont' }}>Hello, custom font!</Text></View>;
  }
};

export default CustomFontComponent;

In the above code, the useFonts call requires an object where the key is the font name and the value is the font file path. useFonts returns a boolean indicating whether the fonts have successfully loaded.

Step 3: Display the component with custom fonts in Storybook

Setting up your component in Storybook is straightforward. Create a new story file (e.g., CustomFontComponent.stories.js) and define your story:

javascript
import React from 'react';
import { storiesOf } from '@storybook/react-native';
import CustomFontComponent from './CustomFontComponent';

storiesOf('CustomFontComponent', module)
  .add('default view', () => <CustomFontComponent />);

This allows you to view and test components using custom fonts in Storybook.

Summary

By following these steps, you can effectively use the useFonts hook in React Native and Storybook to asynchronously load and display custom fonts, ensuring correct font loading and rendering during development. This enhances development efficiency and application usability.