This is documentation for the next SDK version. For up-to-date documentation, see the latest version (SDK 51).

Expo Brightness

A library that provides access to an API for getting and setting the screen brightness.

Android

iOS

An API to get and set screen brightness.

On Android, there is a global system-wide brightness setting, and each app has its own brightness setting that can optionally override the global setting. It is possible to set either of these values with this API. On iOS, the system brightness setting cannot be changed programmatically; instead, any changes to the screen brightness will persist until the device is locked or powered off.

Installation

Terminal

- npx expo install expo-brightness

If you are installing this in an existing React Native app (bare workflow), start by installing expo in your project. Then, follow the additional instructions as mentioned by library's README under "Installation in bare React Native projects" section.

Configuration

Are you using this library in a bare React Native app?

Learn how to configure the native projects in the installation instructions in the expo-brightness repository.

Usage

Basic Brightness Usage

import React, { useEffect } from 'react';
import { StyleSheet, View, Text } from 'react-native';
import * as Brightness from 'expo-brightness';

export default function App() {
  useEffect(() => {
    (async () => {
      const { status } = await Brightness.requestPermissionsAsync();
      if (status === 'granted') {
        Brightness.setSystemBrightnessAsync(1);
      }
    })();
  }, []);

  return (
    <View style={styles.container}>
      <Text>Brightness Module Example</Text>
    </View>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#fff',
    alignItems: 'center',
    justifyContent: 'center',
  },
});

API

import * as Brightness from 'expo-brightness';

Hooks

Android

iOS

`usePermissions(options)`

Name	Type
options (optional)	`PermissionHookOptions<object>`

Check or request permissions to modify the system brightness. This uses both requestPermissionAsync and getPermissionsAsync to interact with the permissions.

Returns:

[null | PermissionResponse, RequestPermissionMethod<PermissionResponse>, GetPermissionMethod<PermissionResponse>]

Example

const [permissionResponse, requestPermission] = Brightness.usePermissions();

Methods

Android

iOS

`Brightness.getBrightnessAsync()`

Gets the current brightness level of the device's main screen.

Returns:

Promise<number>

A Promise that fulfils with a number between 0 and 1, inclusive, representing the current screen brightness.

Android

iOS

`Brightness.getPermissionsAsync()`

Checks user's permissions for accessing system brightness.

Returns:

Promise<PermissionResponse>

A promise that fulfils with an object of type PermissionResponse.

Android

`Brightness.getSystemBrightnessAsync()`

Gets the global system screen brightness.

Returns:

Promise<number>

A Promise that is resolved with a number between 0 and 1, inclusive, representing the current system screen brightness.

Android

`Brightness.getSystemBrightnessModeAsync()`

Gets the system brightness mode (e.g. whether or not the OS will automatically adjust the screen brightness depending on ambient light).

Returns:

Promise<BrightnessMode>

A Promise that fulfils with a BrightnessMode. Requires SYSTEM_BRIGHTNESS permissions.

Android

iOS

`Brightness.isAvailableAsync()`

Returns whether the Brightness API is enabled on the current device. This does not check the app permissions.

Returns:

Promise<boolean>

Async boolean, indicating whether the Brightness API is available on the current device. Currently this resolves true on iOS and Android only.

Android

`Brightness.isUsingSystemBrightnessAsync()`

Returns a boolean specifying whether or not the current activity is using the system-wide brightness value.

Returns:

Promise<boolean>

A Promise that fulfils with true when the current activity is using the system-wide brightness value, and false otherwise.

Android

iOS

`Brightness.requestPermissionsAsync()`

Asks the user to grant permissions for accessing system brightness.

Returns:

Promise<PermissionResponse>

A promise that fulfils with an object of type PermissionResponse.

Android

`Brightness.restoreSystemBrightnessAsync()`

Resets the brightness setting of the current activity to use the system-wide brightness value rather than overriding it.

Returns:

Promise<void>

A Promise that fulfils when the setting has been successfully changed.

Android

iOS

`Brightness.setBrightnessAsync(brightnessValue)`

Name	Type	Description
brightnessValue	`number`	A number between `0` and `1`, inclusive, representing the desired screen brightness.

Sets the current screen brightness. On iOS, this setting will persist until the device is locked, after which the screen brightness will revert to the user's default setting. On Android, this setting only applies to the current activity; it will override the system brightness value whenever your app is in the foreground.

Returns:

Promise<void>

A Promise that fulfils when the brightness has been successfully set.

Experimental

•

Android

`Brightness.setSystemBrightnessAsync(brightnessValue)`

Name	Type	Description
brightnessValue	`number`	A number between `0` and `1`, inclusive, representing the desired screen brightness.

Sets the global system screen brightness and changes the brightness mode to MANUAL. Requires SYSTEM_BRIGHTNESS permissions.

Returns:

Promise<void>

A Promise that fulfils when the brightness has been successfully set.

Android

`Brightness.setSystemBrightnessModeAsync(brightnessMode)`

Name	Type	Description
brightnessMode	`BrightnessMode`	One of `BrightnessMode.MANUAL` or `BrightnessMode.AUTOMATIC`. The system brightness mode cannot be set to `BrightnessMode.UNKNOWN`.

Sets the system brightness mode.

Returns:

Promise<void>

Deprecated Use restoreSystemBrightnessAsync method instead.

Android

`Brightness.useSystemBrightnessAsync()`

Returns:

Promise<void>

Event Subscriptions

iOS

`Brightness.addBrightnessListener(listener)`

Name	Type	Description
listener	`(event: BrightnessEvent) => void`	A callback that is invoked when brightness (iOS) changes. The callback is provided a single argument that is an object with a `brightness` key.

Subscribe to brightness (iOS) updates. The event fires whenever the power mode is toggled.

On web and android the event never fires.

Returns:

EventSubscription

A Subscription object on which you can call remove() to unsubscribe from the listener.

Interfaces

Android

iOS

`PermissionResponse`

An object obtained by permissions get and request functions.

PermissionResponse Properties

Name	Type	Description
canAskAgain	`boolean`	Indicates if user can be asked again for specific permission. If not, one should be directed to the Settings app in order to enable/disable the permission.
expires	`PermissionExpiration`	Determines time when the permission expires.
granted	`boolean`	A convenience boolean that indicates if the permission is granted.
status	`PermissionStatus`	Determines the status of the permission.