Screen capture

Preventing capture is held by a key, and stays on while any key is held: a payment screen and a passwords screen that each prevent it do not undo each other when one of them closes. The screenshot count is a signal, and the listener behind it lives as long as the app does and is removed when the app is destroyed.

Install

npx expo install expo-screen-capture

import { ScreenCapture } from '@ng-native/expo/screen-capture';

The smallest useful example

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

@Component({
  selector: 'app-card-details',
  imports: [Text],
  template: `
    <text>4242 4242 4242 4242</text>
    @if (capture.screenshots() > 0) {
      <text>Screenshots of this screen show your card number.</text>
    }
  `,
})
export class CardDetails {
  protected readonly capture = inject(ScreenCapture);

  constructor() {
    void this.capture.prevent('card-details');
    inject(DestroyRef).onDestroy(() => void this.capture.allow('card-details'));
  }
}

What it does

• screenshots - a signal: how many screenshots the user has taken while the app was in front. The event carries nothing else, so a count is all there is to hold.
• prevent(key?) - keeps the app out of screenshots and screen recordings until allow() is called with the same key, or the app is destroyed. Without a key, one shared default key is used. Keys are counted across every app the runtime mounts, so an app allowing a key leaves it held for another app that prevents it too. On Android, an activity that comes to the front while a key is held is kept out of capture again.
• allow(key?) - releases the key. Capture is allowed again once no key is held.
• available() - whether the platform can prevent capture.
• protectAppSwitcher(blurIntensity?) and unprotectAppSwitcher() - hide the app's content in the app switcher and leave screenshots allowed. iOS: blurs the app while it is not in focus - in the app switcher, in the background, during interruptions - by an intensity from 0 to 1, half by default. Android 13 and later: leaves the app's snapshot out of recent apps, including after the activity is recreated, through this package's native half, so it needs a development build; the intensity is not used. Earlier Android, and Expo Go on Android, do nothing: prevent() hides the app in recent apps there, and blocks screenshots too.
• permission - a Permission for screenshot detection. Android 13 and earlier need it, since detection reads the photo library; later Android needs none, and iOS always answers granted.

Without the module

On iOS and Android, a missing expo-screen-capture - 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, screenshots stays at 0, available() resolves to false, the permission is refused, and every other method resolves without doing anything.

Reference