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 Device	Android Emulator	iOS Device	iOS Simulator	Web

Installation

expo install expo-brightness

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

Usage

import React, { useEffect } from 'react';
import { 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={{
        flex: 1,
        backgroundColor: '#fff',
        alignItems: 'center',
        justifyContent: 'center',
      }}>
      <Text>Brightness Module Example</Text>
    </View>
  );
}

API

import * as Brightness from 'expo-brightness';

Methods

`Brightness.isAvailableAsync()`

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

Returns

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

`Brightness.requestPermissionsAsync()`

Asks the user to grant permissions for accessing system brightness. Alias for Permissions.askAsync(Permissions.BRIGHTNESS).

Returns

A promise that resolves to an object of type PermissionResponse.

`Brightness.getPermissionsAsync()`

Checks user's permissions for accessing system brightness. Alias for Permissions.getAsync(Permissions.BRIGHTNESS).

Returns

A promise that resolves to an object of type PermissionResponse.

`Brightness.getBrightnessAsync()`

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

Returns

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

`Brightness.setBrightnessAsync(brightnessValue)`

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.

Arguments

brightnessValue (number) - A number between 0 and 1, inclusive, representing the desired screen brightness.

Returns

A Promise that is resolved when the brightness has been successfully set.

Error Codes

ERR_BRIGHTNESS

`Brightness.useSystemBrightnessAsync()`

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

Returns

A Promise that is resolved when the setting has been successfully changed.

`Brightness.isUsingSystemBrightnessAsync()`

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

Returns

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

Error Codes

ERR_BRIGHTNESS

`Brightness.getSystemBrightnessAsync()`

Android only. Gets the global system screen brightness.

Returns

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

Error Codes

ERR_BRIGHTNESS_SYSTEM

`Brightness.setSystemBrightnessAsync(brightnessValue)`

WARNING: This method is experimental.

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

Arguments

brightnessValue (number) - A number between 0 and 1, inclusive, representing the desired screen brightness.

Returns

A Promise that is resolved when the brightness has been successfully set.

Error Codes

`Brightness.getSystemBrightnessModeAsync()`

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

Returns

A Promise that is resolved with a BrightnessMode. Requires SYSTEM_BRIGHTNESS permissions.

Error Codes

ERR_BRIGHTNESS_MODE

`Brightness.setSystemBrightnessModeAsync(brightnessMode)`

Android only. Sets the system brightness mode.

Arguments

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

Returns

A Promise that is resolved when the brightness mode has been successfully set.

Error Codes

Enum Types

Brightness.BrightnessMode

BrightnessMode.AUTOMATIC - Mode in which the device OS will automatically adjust the screen brightness depending on the ambient light.
BrightnessMode.MANUAL - Mode in which the screen brightness will remain constant and will not be adjusted by the OS.
BrightnessMode.UNKNOWN - Means that the current brightness mode cannot be determined.