useAppLifecycle

A react native hook to run code when your app is launched, focused and blurred.

Install

yarn add @pachun/react-native-use-app-lifecycle

Usage

In your topmost-level component:

import useAppLifecycle from "@pachun/react-native-use-app-lifecycle"

const App = () => {
  useAppLifecycle({
    onLaunch: () => console.log("launch"),
    onFocus: () => console.log("focus"),
    onBlur: () => console.log("blur"),
  })

  return <></>
}

export default App

onLaunch runs once, when the hook first mounts. onFocus and onBlur run on the transitions to and from the foreground — and onFocus is debounced ~100ms, so a burst of blur/focus events (a lock-screen flicker, Control Center) fires it once.

[!TIP] I use this package to check for and download Over-The-Air (OTA) expo updates.

Motivation

ref code ruins behavior driven development. Use this package to make your tests tell a coherent story.

Tests

import { renderRouter, waitFor, screen } from "expo-router/testing-library"
import launchTheApp from "@pachun/react-native-use-app-lifecycle/testing"

describe("foregrounding the application", () => {
  it("refreshes the inbox", async () => {
    const { backgroundTheApp, foregroundTheApp } = launchTheApp(() =>
      renderRouter("src/app", { initialUrl: "/" }),
    )

    backgroundTheApp()
    foregroundTheApp()

    await waitFor(() => expect(screen.getByText("1 new email")).toBeTruthy())
  })
})

launchTheApp takes whatever renders your app; renderRouter, render, renderHook.

[!NOTE] It's jest-only, and it uses act from @testing-library/react-native — which you already have if you're testing with expo-router/testing-library.

Contributing

PRs are exciting 🤟 Bump the version number in package.json and open one.

• Please keep coverage at or above where it is when you clone the repo (yarn test --collectCoverage).