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Expo Application Services
API Reference

Brightness

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.

Platform Compatibility

Android DeviceAndroid EmulatoriOS DeviceiOS SimulatorWeb
Status-success-iconStatus-success-iconStatus-success-iconStatus-success-iconStatus-failed-icon

Installation

Terminal
→ npx expo install expo-brightness

If you're installing this in a bare React Native app, you should also follow these additional installation instructions.

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>
  );
}

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

API

import * as Brightness from 'expo-brightness';

Hooks

usePermissions(options)

NameTypeDescription
options
(optional)
PermissionHookOptions<object>-

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

Example

const [permissionResponse, requestPermission] = Brightness.usePermissions();
  • Undo-icon[null | PermissionResponse, RequestPermissionMethod<PermissionResponse>, GetPermissionMethod<PermissionResponse>]

Methods

Brightness.getBrightnessAsync()

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

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

Brightness.getPermissionsAsync()

Checks user's permissions for accessing system brightness.

A promise that fulfils with an object of type PermissionResponse.

Only for:
Android-iconAndroid

Brightness.getSystemBrightnessAsync()

Gets the global system screen brightness.

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

Only for:
Android-iconAndroid

Brightness.getSystemBrightnessModeAsync()

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

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

Brightness.isAvailableAsync()

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

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

Only for:
Android-iconAndroid

Brightness.isUsingSystemBrightnessAsync()

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

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

Brightness.requestPermissionsAsync()

Asks the user to grant permissions for accessing system brightness.

A promise that fulfils with an object of type PermissionResponse.

Brightness.setBrightnessAsync(brightnessValue)

NameTypeDescription
brightnessValuenumber

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.

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

Only for:
Android-iconAndroid

Brightness.setSystemBrightnessAsync(brightnessValue)

NameTypeDescription
brightnessValuenumber

A number between 0 and 1, inclusive, representing the desired screen brightness.

Info-icon

WARNING: This method is experimental.

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

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

Only for:
Android-iconAndroid

Brightness.setSystemBrightnessModeAsync(brightnessMode)

NameTypeDescription
brightnessModeBrightnessMode

One of BrightnessMode.MANUAL or BrightnessMode.AUTOMATIC. The system brightness mode cannot be set to BrightnessMode.UNKNOWN.

Sets the system brightness mode.

Only for:
Android-iconAndroid

Brightness.useSystemBrightnessAsync()

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

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

Event Subscriptions

Only for:
Apple-iconiOS

Brightness.addBrightnessListener(listener)

NameTypeDescription
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.

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

Interfaces

PermissionResponse

An object obtained by permissions get and request functions.

NameTypeDescription
canAskAgainbooleanIndicates 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.
expiresPermissionExpirationDetermines time when the permission expires.
grantedbooleanA convenience boolean that indicates if the permission is granted.
statusPermissionStatusDetermines the status of the permission.

Types

BrightnessEvent

NameTypeDescription
brightnessnumberA number between 0 and 1, inclusive, representing the current screen brightness.

PermissionExpiration

Permission expiration time. Currently, all permissions are granted permanently.

Acceptable values are: 'never', number.

PermissionHookOptions

Acceptable values are: PermissionHookBehavior, Options.

Enums

BrightnessMode

BrightnessMode.UNKNOWN = 0

Means that the current brightness mode cannot be determined.

BrightnessMode.AUTOMATIC = 1

Mode in which the device OS will automatically adjust the screen brightness depending on the ambient light.

BrightnessMode.MANUAL = 2

Mode in which the screen brightness will remain constant and will not be adjusted by the OS.

PermissionStatus

PermissionStatus.DENIED = "denied"

User has denied the permission.

PermissionStatus.GRANTED = "granted"

User has granted the permission.

PermissionStatus.UNDETERMINED = "undetermined"

User hasn't granted or denied the permission yet.

Error Codes

ERR_BRIGHTNESS

An error occurred when getting or setting the app brightness.

ERR_BRIGHTNESS_MODE

An error occurred when getting or setting the system brightness mode. See the nativeError property of the thrown error for more information.

ERR_BRIGHTNESS_PERMISSIONS_DENIED

An attempt to set the system brightness was made without the proper permissions from the user. The user did not grant SYSTEM_BRIGHTNESS permissions.

ERR_BRIGHTNESS_SYSTEM

An error occurred when getting or setting the system brightness.

ERR_INVALID_ARGUMENT

An invalid argument was passed. Only BrightnessMode.MANUAL or BrightnessMode.AUTOMATIC are allowed.
  • Message-iconAsk a question on the forums about Brightness
  • Github-iconView open bug reports for Brightness
  • Code-iconView source code for Brightness
  • Build-iconView package in npm Registry
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