Simplifying Cross-Platform Mobile App Development with Expo
Expo is revolutionizing the way we build cross-platform iOS and Android mobile apps. This open-source platform makes it easier than ever to access native device features, such as cameras, push notifications, and local storage, using JavaScript.
Getting Started with Expo
To install Expo, you’ll need Node.js version 12 or newer on your machine. Expo’s command-line tools and dependency management rely on the Node platform. You can check your Node version by running the Node -v command in your terminal.
Building an Expo App
Creating an Expo app is a breeze. Simply run the command expo init my-app (replace “my-app” with your desired app name), select a template, and follow the prompts to install the necessary dependencies. Once you’ve completed these steps, you can start your project with the command expo start.
Understanding Expo Project Structure
Your Expo project consists of several important files:
App.json: contains app configurations, such as app name, SDK version, icon, and more.package.json: lists the app’s dependencies.App.js: runs when the app starts and contains the render method, which wraps all components inside a single component within the return statement.
Expo SDK: A Treasure Trove of Libraries
Expo comes with a wealth of built-in libraries that cater to most app development needs. Some of the notable libraries include:
- AppAuth and AuthSession for user authentication via OAuth
- SplashScreen for creating a splash screen when launching the app
- Localization for managing l10n/i18n of your application
- AppLoading for loading assets, fonts, and more
- MapView for using maps inside the app
- ImagePicker/ImageManipulator for opening images or videos from the device
Creating a Splash Screen with Expo
Let’s create a splash screen using Expo. First, create an image in.png format and place it in your app directory. Then, install the expo-splash-screen library using the command expo install expo-splash-screen. Create a new file, import the library, and create a function to display the splash screen.
Publishing and Uploading Your App to Stores
When you’re ready to release your app, Expo offers a few options to select. You can use the command expo build:ios or expo build:android to build your app on the cloud. Once the build is complete, you can upload it to the app stores using the command expo publish.
New Features Added to Expo in 2021
Expo has introduced several exciting features in 2021, including:
- Integrated developer tools for accessing the developer menu, inspecting components, and tracking results
- Force reloading for reloading attached computers, laptops, simulators, and browsers
- Automatic setup for TypeScript
- Significantly better errors with descriptive, useful, and practical error messages
- Improved Apple Store interactions and the ability to connect through your terminal
Limitations of Expo
While Expo offers a wide range of features, there are some limitations to be aware of:
- Background code execution is not supported by Expo applications.
- Expo apps are confined to the native APIs supported by the Expo SDK.
- Expo binds you to their set of tools.
- Standalone binaries in Expo apps can only be built when they are online.
Despite these limitations, Expo is a valuable platform that simplifies cross-platform mobile app development. Its extensive support for prominent Android and iOS APIs makes it an ideal choice for most app development needs.