Camera access (expo-camera) in React Native

Introduction

We use the camera in apps to take pictures or record videos. It helps users capture moments or scan things easily.

When you want users to take a photo inside your app, like for a profile picture.

When your app needs to scan QR codes or barcodes.

When users want to record videos directly from your app.

When you want to build a photo editing or sharing app.

When you want to add augmented reality features that use the camera view.

Syntax

React Native

import { Camera } from 'expo-camera';
import React, { useState, useEffect } from 'react';
import { View, Text } from 'react-native';

const [hasPermission, setHasPermission] = useState(null);
const [cameraRef, setCameraRef] = useState(null);

useEffect(() => {
  (async () => {
    const { status } = await Camera.requestCameraPermissionsAsync();
    setHasPermission(status === 'granted');
  })();
}, []);

return (
  hasPermission === null ? <View /> :
  hasPermission === false ? <Text>No access to camera</Text> :
  <Camera ref={ref => setCameraRef(ref)} style={{ flex: 1 }} />
);

Camera.requestCameraPermissionsAsync() asks the user to allow camera use.

You must check permission before showing the camera to avoid errors.

Examples

Request camera permission and check if user allowed it.

React Native

const { status } = await Camera.requestCameraPermissionsAsync();
if (status === 'granted') {
  // Permission granted
}

Show the camera preview filling the screen.

React Native

<Camera style={{ flex: 1 }} />

Take a picture using the camera reference.

React Native

const takePicture = async () => {
  if (cameraRef) {
    const photo = await cameraRef.takePictureAsync();
    console.log(photo.uri);
  }
};

Sample App

This app asks for camera permission, shows the camera preview, and has a button to take a picture. When you tap the button, it takes a photo and shows the file path below.

React Native

import React, { useState, useEffect } from 'react';
import { Text, View, TouchableOpacity } from 'react-native';
import { Camera } from 'expo-camera';

export default function App() {
  const [hasPermission, setHasPermission] = useState(null);
  const [cameraRef, setCameraRef] = useState(null);
  const [photoUri, setPhotoUri] = useState(null);

  useEffect(() => {
    (async () => {
      const { status } = await Camera.requestCameraPermissionsAsync();
      setHasPermission(status === 'granted');
    })();
  }, []);

  const takePicture = async () => {
    if (cameraRef) {
      const photo = await cameraRef.takePictureAsync();
      setPhotoUri(photo.uri);
    }
  };

  if (hasPermission === null) {
    return <View />;
  }
  if (hasPermission === false) {
    return <Text>No access to camera</Text>;
  }

  return (
    <View style={{ flex: 1 }}>
      <Camera style={{ flex: 4 }} ref={ref => setCameraRef(ref)} />
      <TouchableOpacity
        onPress={takePicture}
        style={{ flex: 1, justifyContent: 'center', alignItems: 'center', backgroundColor: '#2196F3' }}
        accessibilityLabel="Take picture button"
      >
        <Text style={{ color: 'white', fontSize: 18 }}>Take Picture</Text>
      </TouchableOpacity>
      {photoUri && <Text style={{ padding: 10 }}>Photo saved at: {photoUri}</Text>}
    </View>
  );
}

Important Notes

Always ask for camera permission before using the camera.

Use the camera reference to control the camera and take pictures.

Remember to handle the case when permission is denied to inform the user.

Summary

Camera access lets your app take photos or videos inside the app.

Request permission first, then show the camera preview.

Use the camera reference to take pictures and get their file paths.

Practice

1. What is the first step to use the camera in a React Native app with expo-camera?

easy

A. Directly show the camera preview

B. Request permission to access the camera

C. Take a picture immediately

D. Install a photo editing library

Solution

1. Step 1: Understand permission requirement

   Mobile apps must ask user permission before accessing hardware like the camera.

2. Step 2: Request camera permission first

   Using expo-camera, you call permission request functions before showing the camera.

3. Final Answer:

   Request permission to access the camera -> Option B

4. Quick Check:

   Permission request = A [OK]

Hint: Always ask permission before using hardware [OK]

Common Mistakes:

• Trying to show camera preview without permission
• Taking picture before permission granted
• Skipping permission request step

2. Which of the following is the correct way to import the Camera component from expo-camera?

easy

A. import Camera from 'expo-camera';

B. import CameraComponent from 'expo-camera';

C. import * as Camera from 'expo-camera';

D. import { Camera } from 'expo-camera';

Solution

1. Step 1: Check expo-camera export style

   The Camera component is a named export, so it must be imported with curly braces.

2. Step 2: Use correct import syntax

   Correct syntax is import { Camera } from 'expo-camera'; to access the Camera component.

3. Final Answer:

   import { Camera } from 'expo-camera'; -> Option D

4. Quick Check:

   Named import uses curly braces = D [OK]

Hint: Named exports need curly braces in import [OK]

Common Mistakes:

• Using default import without braces
• Importing everything as an object
• Using wrong import names

3. What will be the output of this code snippet inside a React Native component using expo-camera?

const [hasPermission, setHasPermission] = React.useState(null);
React.useEffect(() => {
  (async () => {
    const { status } = await Camera.requestCameraPermissionsAsync();
    setHasPermission(status === 'granted');
  })();
}, []);

return hasPermission === null ? Requesting permission : hasPermission === false ? No access : ;

medium

A. Shows camera preview immediately without permission

B. Shows 'No access' text always

C. Shows 'Requesting permission' text initially, then camera preview if granted

D. Throws a syntax error

Solution

1. Step 1: Analyze permission state flow

   Initially, hasPermission is null, so it shows 'Requesting permission'.

2. Step 2: After permission request

   If permission granted, hasPermission becomes true and camera preview shows; if denied, shows 'No access'.

3. Final Answer:

   Shows 'Requesting permission' text initially, then camera preview if granted -> Option C

4. Quick Check:

   Permission null -> text, granted -> camera = B [OK]

Hint: Check initial state null shows loading text [OK]

Common Mistakes:

• Expecting camera preview before permission granted
• Confusing permission states
• Ignoring async permission request

4. Identify the error in this React Native code snippet using expo-camera:

const cameraRef = React.useRef(null);

async function takePicture() {
  if (cameraRef) {
    const photo = await cameraRef.current.takePictureAsync();
    console.log(photo.uri);
  }
}

medium

A. cameraRef should be checked as cameraRef.current, not cameraRef

B. takePictureAsync() is not an async function

C. cameraRef must be a state variable, not a ref

D. console.log cannot print photo.uri

Solution

1. Step 1: Check cameraRef usage

   cameraRef is a ref object; to access the camera instance, use cameraRef.current.

2. Step 2: Correct condition check

   The condition should check if (cameraRef.current) to ensure the camera is ready.

3. Final Answer:

   cameraRef should be checked as cameraRef.current, not cameraRef -> Option A

4. Quick Check:

   Ref object needs .current to access value = C [OK]

Hint: Check .current on refs before use [OK]

Common Mistakes:

• Checking ref object directly instead of .current
• Forgetting async on takePictureAsync
• Misusing console.log for URIs

5. You want to build a React Native app that takes a photo only if the user grants camera permission and then saves the photo URI in state. Which sequence of steps is correct?

hard

A. Request permission -> Show camera preview -> Use ref to take picture -> Save URI in state

B. Show camera preview -> Take picture -> Request permission -> Save URI in state

C. Take picture -> Request permission -> Show camera preview -> Save URI in state

D. Save URI in state -> Request permission -> Show camera preview -> Take picture

Solution

1. Step 1: Request permission before camera use

   Always ask and confirm permission before showing camera preview.

2. Step 2: Show camera preview and take picture

   Use a ref to access the camera and take a picture only after permission granted.

3. Step 3: Save photo URI in state

   Store the photo URI in state to use or display later in the app.

4. Final Answer:

   Request permission -> Show camera preview -> Use ref to take picture -> Save URI in state -> Option A

5. Quick Check:

   Permission first, then camera, then save = A [OK]

Hint: Permission first, then camera, then save URI [OK]

Common Mistakes:

• Taking picture before permission
• Saving URI before picture taken
• Showing camera without permission