Device Features: Camera & Permissions

The phone can do more than a browser

A real strength of mobile is the hardware: camera, photo library, location, contacts. Expo gives you ready-made modules for these. The golden rule: you must ask permission before touching anything private.

For picking a photo you install Expo Image Picker (one-time):

npx expo install expo-image-picker

Ask, then open the picker

First request permission, then — only if granted — open the photo picker:

import * as ImagePicker from 'expo-image-picker';

async function pickPhoto() {
  const perm = await ImagePicker.requestMediaLibraryPermissionsAsync();
  if (perm.status !== 'granted') {
    console.log('Permission denied');
    return;
  }
  const result = await ImagePicker.launchImageLibraryAsync();
  if (!result.canceled) {
    console.log('Picked:', result.assets[0].uri);
  }
}

• Always request permission before using a private feature.
• Check the status — never assume it was granted.
• If denied, show a kind message; do not crash or nag endlessly.

The pattern is always the same three steps, whatever the feature: ask for permission, check you got it, then use the feature. Camera, location and contacts all follow it.

The whole permission flow, step by step

Here is exactly what happens when the user taps your "Pick photo" button, in order:

1. The user taps the button, which runs your pickPhoto function.
2. Ask: await ImagePicker.requestMediaLibraryPermissionsAsync() shows the phone’s own pop-up: "Allow this app to access your photos?".
3. The user taps Allow or Don’t Allow. The result comes back as an object stored in perm, and perm.status is the string 'granted' or 'denied'.
4. Check: the if (perm.status !== 'granted') line tests that string. If it is not 'granted', you log "Permission denied" and return — stopping before you ever open the picker.
5. Use: only if permission was granted, await ImagePicker.launchImageLibraryAsync() opens the photo gallery so the user can choose a picture.
6. The user either picks a photo or taps cancel. result.canceled tells you which: the if (!result.canceled) line runs only when they actually chose one.
7. When they did pick, result.assets[0].uri is the address of the chosen photo (here logged as Picked: file:///path/to/photo.jpg) — ready to show in an Image.

What works where

A common beginner trip-up is expecting every device feature to run inside Expo Go. Many do; a few need a heavier setup called a development build. Here is the quick guide: