Brightness

The app's own brightness only. The system brightness is a global setting an app can leave changed after it is gone, and needs a permission on Android, so reaching for it is a decision to make deliberately against Expo's own API rather than a convenience this offers.

Install

npx expo install expo-brightness

import { Brightness } from '@ng-native/expo/brightness';

The smallest useful example

import { Component, DestroyRef, inject } from '@angular/core';
import { Text } from '@ng-native/components';
import { Brightness } from '@ng-native/expo/brightness';

@Component({
  selector: 'app-boarding-pass',
  imports: [Text],
  template: `<text>Show this at the gate</text>`,
})
export class BoardingPass {
  private readonly brightness = inject(Brightness);

  constructor() {
    const restore = this.brightness.set(1);
    inject(DestroyRef).onDestroy(restore);
  }
}

What it does

• level - a signal, nought to one. Starts at 1, since that is what a screen already shows before anything asks the platform.
• set(level) - clamps to 0..1, applies it, and returns the function that puts back what was there before: the level an earlier set() still holds, such as the screen underneath a pushed one, or the system's own brightness once nothing does. Always use the returned function rather than calling restore() separately: an app that leaves the screen at full brightness after showing a boarding pass is one the user experiences as a battery fault, not a bug they can name.
• restore() - puts back at once every level this app still has set: the system's brightness, or the level of another app the runtime mounts that still has one. Available directly if a screen needs to put the brightness back without waiting for teardown.

Levels stack across every app the runtime mounts, and an app that is destroyed puts back its own. On Android, an activity that comes to the front is given the level again.

iOS has no window level of the app's own: the level set is the screen's, and it stays after the app until the device locks. So when no app holds a level, the next set() first reads the level the screen has. When the last level is dropped, or restore() is called, that level is set again, so a change made in Control Center while a level was held is undone. If the level cannot be read, nothing is put back. Leaving the app while a level is held, without dropping it, keeps the screen at that level until the device locks.

Without the module

On iOS and Android, a missing expo-brightness - never installed, or installed without the app being rebuilt since - leaves the service made, so injecting it does not throw. A call, or a read of a value only the module knows, throws a MissingModuleError. Its message names the module and the commands that fix it; see Using a module.

On the web, and in a test that provides no fake, level stays at 1. set() and restore() do nothing and do not throw.

Reference