Agent skill
expo-modules
Use when working with Expo SDK modules for camera, location, notifications, file system, and other device APIs. Covers permissions, configurations, and best practices.
Install this agent skill to your Project
npx add-skill https://github.com/TheBushidoCollective/han/tree/main/plugins/frameworks/expo/skills/expo-modules
SKILL.md
Expo Modules
Use this skill when working with Expo's extensive SDK modules for accessing device features and native functionality.
Key Concepts
Camera
import { Camera, CameraType } from 'expo-camera';
import { useState } from 'react';
import { Button, View } from 'react-native';
export default function CameraScreen() {
const [permission, requestPermission] = Camera.useCameraPermissions();
const [type, setType] = useState(CameraType.back);
if (!permission?.granted) {
return (
<View>
<Button title="Grant Permission" onPress={requestPermission} />
</View>
);
}
return (
<Camera style={{ flex: 1 }} type={type}>
<Button
title="Flip Camera"
onPress={() =>
setType(type === CameraType.back ? CameraType.front : CameraType.back)
}
/>
</Camera>
);
}
Location
import * as Location from 'expo-location';
import { useEffect, useState } from 'react';
export function useLocation() {
const [location, setLocation] = useState<Location.LocationObject | null>(null);
useEffect(() => {
(async () => {
const { status } = await Location.requestForegroundPermissionsAsync();
if (status !== 'granted') return;
const loc = await Location.getCurrentPositionAsync({});
setLocation(loc);
})();
}, []);
return location;
}
Notifications
import * as Notifications from 'expo-notifications';
import { useEffect } from 'react';
Notifications.setNotificationHandler({
handleNotification: async () => ({
shouldShowAlert: true,
shouldPlaySound: true,
shouldSetBadge: false,
}),
});
export function useNotifications() {
useEffect(() => {
const subscription = Notifications.addNotificationReceivedListener(
(notification) => {
console.log(notification);
}
);
return () => subscription.remove();
}, []);
const sendNotification = async () => {
await Notifications.scheduleNotificationAsync({
content: {
title: 'Hello!',
body: 'This is a notification',
},
trigger: { seconds: 2 },
});
};
return { sendNotification };
}
File System
import * as FileSystem from 'expo-file-system';
export async function saveFile(data: string, filename: string) {
const uri = `${FileSystem.documentDirectory}${filename}`;
await FileSystem.writeAsStringAsync(uri, data);
return uri;
}
export async function readFile(filename: string) {
const uri = `${FileSystem.documentDirectory}${filename}`;
const content = await FileSystem.readAsStringAsync(uri);
return content;
}
export async function downloadFile(url: string, filename: string) {
const uri = `${FileSystem.documentDirectory}${filename}`;
const download = await FileSystem.downloadAsync(url, uri);
return download.uri;
}
Image Picker
import * as ImagePicker from 'expo-image-picker';
import { useState } from 'react';
import { Button, Image, View } from 'react-native';
export default function ImagePickerScreen() {
const [image, setImage] = useState<string | null>(null);
const pickImage = async () => {
const result = await ImagePicker.launchImageLibraryAsync({
mediaTypes: ImagePicker.MediaTypeOptions.Images,
allowsEditing: true,
aspect: [4, 3],
quality: 1,
});
if (!result.canceled) {
setImage(result.assets[0].uri);
}
};
return (
<View>
<Button title="Pick Image" onPress={pickImage} />
{image && <Image source={{ uri: image }} style={{ width: 200, height: 200 }} />}
</View>
);
}
Best Practices
Permission Handling
import * as Location from 'expo-location';
async function requestLocationPermission() {
const { status: foregroundStatus } =
await Location.requestForegroundPermissionsAsync();
if (foregroundStatus !== 'granted') {
console.log('Permission denied');
return false;
}
// Request background permission only if needed
const { status: backgroundStatus } =
await Location.requestBackgroundPermissionsAsync();
return backgroundStatus === 'granted';
}
Secure Storage
import * as SecureStore from 'expo-secure-store';
export async function saveToken(key: string, value: string) {
await SecureStore.setItemAsync(key, value);
}
export async function getToken(key: string) {
return await SecureStore.getItemAsync(key);
}
export async function deleteToken(key: string) {
await SecureStore.deleteItemAsync(key);
}
Device Info
import * as Device from 'expo-device';
import * as Application from 'expo-application';
import Constants from 'expo-constants';
export function getDeviceInfo() {
return {
deviceName: Device.deviceName,
deviceType: Device.deviceType,
osName: Device.osName,
osVersion: Device.osVersion,
appVersion: Application.nativeApplicationVersion,
buildVersion: Application.nativeBuildVersion,
expoVersion: Constants.expoVersion,
};
}
Common Patterns
Persistent Storage
import AsyncStorage from '@react-native-async-storage/async-storage';
export const storage = {
async set(key: string, value: any) {
await AsyncStorage.setItem(key, JSON.stringify(value));
},
async get<T>(key: string): Promise<T | null> {
const item = await AsyncStorage.getItem(key);
return item ? JSON.parse(item) : null;
},
async remove(key: string) {
await AsyncStorage.removeItem(key);
},
async clear() {
await AsyncStorage.clear();
},
};
Background Tasks
import * as BackgroundFetch from 'expo-background-fetch';
import * as TaskManager from 'expo-task-manager';
const BACKGROUND_FETCH_TASK = 'background-fetch';
TaskManager.defineTask(BACKGROUND_FETCH_TASK, async () => {
// Do work here
console.log('Background task running');
return BackgroundFetch.BackgroundFetchResult.NewData;
});
export async function registerBackgroundTask() {
return BackgroundFetch.registerTaskAsync(BACKGROUND_FETCH_TASK, {
minimumInterval: 60 * 15, // 15 minutes
stopOnTerminate: false,
startOnBoot: true,
});
}
Sharing Content
import * as Sharing from 'expo-sharing';
export async function shareContent(uri: string) {
const isAvailable = await Sharing.isAvailableAsync();
if (!isAvailable) {
console.log('Sharing is not available');
return;
}
await Sharing.shareAsync(uri, {
mimeType: 'image/jpeg',
dialogTitle: 'Share this image',
});
}
Related Skills
- expo-config: Configuring module permissions
- expo-build: Including modules in builds
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