/**
 * @license
 * Copyright Google Inc. All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */
import { Observable } from 'rxjs';
import { NgswCommChannel, UpdateActivatedEvent, UpdateAvailableEvent } from './low_level';
/**
 * Subscribe to update notifications from the Service Worker, trigger update
 * checks, and forcibly activate updates.
 *
 * @publicApi
 */
export declare class SwUpdate {
    private sw;
    /**
     * Emits an `UpdateAvailableEvent` event whenever a new app version is available.
     */
    readonly available: Observable<UpdateAvailableEvent>;
    /**
     * Emits an `UpdateActivatedEvent` event whenever the app has been updated to a new version.
     */
    readonly activated: Observable<UpdateActivatedEvent>;
    /**
     * True if the Service Worker is enabled (supported by the browser and enabled via
     * `ServiceWorkerModule`).
     */
    readonly isEnabled: boolean;
    constructor(sw: NgswCommChannel);
    checkForUpdate(): Promise<void>;
    activateUpdate(): Promise<void>;
}