| // Copyright 2014 The Flutter Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| |
| /// Generates the flutter.js file. |
| /// |
| /// flutter.js should be completely static, so **do not use any parameter or |
| /// environment variable to generate this file**. |
| String generateFlutterJsFile() { |
| return ''' |
| // Copyright 2014 The Flutter Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| /** |
| * This script installs service_worker.js to provide PWA functionality to |
| * application. For more information, see: |
| * https://developers.google.com/web/fundamentals/primers/service-workers |
| */ |
| |
| if (!_flutter) { |
| var _flutter = {}; |
| } |
| _flutter.loader = null; |
| |
| (function() { |
| "use strict"; |
| class FlutterLoader { |
| /** |
| * Creates a FlutterLoader, and initializes its instance methods. |
| */ |
| constructor() { |
| // TODO: Move the below methods to "#private" once supported by all the browsers |
| // we support. In the meantime, we use the "revealing module" pattern. |
| |
| // Watchdog to prevent injecting the main entrypoint multiple times. |
| this._scriptLoaded = null; |
| |
| // Resolver for the pending promise returned by loadEntrypoint. |
| this._didCreateEngineInitializerResolve = null; |
| |
| // Called by Flutter web. |
| // Bound to `this` now, so "this" is preserved across JS <-> Flutter jumps. |
| this.didCreateEngineInitializer = this._didCreateEngineInitializer.bind(this); |
| } |
| |
| /** |
| * Initializes the main.dart.js with/without serviceWorker. |
| * @param {*} options |
| * @returns a Promise that will eventually resolve with an EngineInitializer, |
| * or will be rejected with the error caused by the loader. |
| */ |
| loadEntrypoint(options) { |
| const { |
| entrypointUrl = "main.dart.js", |
| serviceWorker, |
| } = (options || {}); |
| return this._loadWithServiceWorker(entrypointUrl, serviceWorker); |
| } |
| |
| /** |
| * Resolves the promise created by loadEntrypoint. |
| * Called by Flutter through the public `didCreateEngineInitializer` method, |
| * which is bound to the correct instance of the FlutterLoader on the page. |
| * @param {*} engineInitializer |
| */ |
| _didCreateEngineInitializer(engineInitializer) { |
| if (typeof this._didCreateEngineInitializerResolve != "function") { |
| console.warn("Do not call didCreateEngineInitializer by hand. Start with loadEntrypoint instead."); |
| } |
| this._didCreateEngineInitializerResolve(engineInitializer); |
| // Remove the public method after it's done, so Flutter Web can hot restart. |
| delete this.didCreateEngineInitializer; |
| } |
| |
| _loadEntrypoint(entrypointUrl) { |
| if (!this._scriptLoaded) { |
| this._scriptLoaded = new Promise((resolve, reject) => { |
| let scriptTag = document.createElement("script"); |
| scriptTag.src = entrypointUrl; |
| scriptTag.type = "application/javascript"; |
| // Cache the resolve, so it can be called from Flutter. |
| // Note: Flutter hot restart doesn't re-create this promise, so this |
| // can only be called once. Instead, we need to model this as a stream |
| // of `engineCreated` events coming from Flutter that are handled by JS. |
| this._didCreateEngineInitializerResolve = resolve; |
| scriptTag.addEventListener("error", reject); |
| document.body.append(scriptTag); |
| }); |
| } |
| |
| return this._scriptLoaded; |
| } |
| |
| _waitForServiceWorkerActivation(serviceWorker, entrypointUrl) { |
| if (!serviceWorker || serviceWorker.state == "activated") { |
| if (!serviceWorker) { |
| console.warn("Cannot activate a null service worker. Falling back to plain <script> tag."); |
| } else { |
| console.debug("Service worker already active."); |
| } |
| return this._loadEntrypoint(entrypointUrl); |
| } |
| return new Promise((resolve, _) => { |
| serviceWorker.addEventListener("statechange", () => { |
| if (serviceWorker.state == "activated") { |
| console.debug("Installed new service worker."); |
| resolve(this._loadEntrypoint(entrypointUrl)); |
| } |
| }); |
| }); |
| } |
| |
| _loadWithServiceWorker(entrypointUrl, serviceWorkerOptions) { |
| if (!("serviceWorker" in navigator) || serviceWorkerOptions == null) { |
| console.warn("Service worker not supported (or configured). Falling back to plain <script> tag.", serviceWorkerOptions); |
| return this._loadEntrypoint(entrypointUrl); |
| } |
| |
| const { |
| serviceWorkerVersion, |
| timeoutMillis = 4000, |
| } = serviceWorkerOptions; |
| |
| let serviceWorkerUrl = "flutter_service_worker.js?v=" + serviceWorkerVersion; |
| let loader = navigator.serviceWorker.register(serviceWorkerUrl) |
| .then((reg) => { |
| if (!reg.active && (reg.installing || reg.waiting)) { |
| // No active web worker and we have installed or are installing |
| // one for the first time. Simply wait for it to activate. |
| let sw = reg.installing || reg.waiting; |
| return this._waitForServiceWorkerActivation(sw, entrypointUrl); |
| } else if (!reg.active.scriptURL.endsWith(serviceWorkerVersion)) { |
| // When the app updates the serviceWorkerVersion changes, so we |
| // need to ask the service worker to update. |
| console.debug("New service worker available."); |
| return reg.update().then((reg) => { |
| console.debug("Service worker updated."); |
| let sw = reg.installing || reg.waiting || reg.active; |
| return this._waitForServiceWorkerActivation(sw, entrypointUrl); |
| }); |
| } else { |
| // Existing service worker is still good. |
| console.debug("Loading app from service worker."); |
| return this._loadEntrypoint(entrypointUrl); |
| } |
| }); |
| |
| // Timeout race promise |
| let timeout; |
| if (timeoutMillis > 0) { |
| timeout = new Promise((resolve, _) => { |
| setTimeout(() => { |
| if (!this._scriptLoaded) { |
| console.warn("Failed to load app from service worker. Falling back to plain <script> tag."); |
| resolve(this._loadEntrypoint(entrypointUrl)); |
| } |
| }, timeoutMillis); |
| }); |
| } |
| |
| return Promise.race([loader, timeout]); |
| } |
| } |
| |
| _flutter.loader = new FlutterLoader(); |
| }()); |
| '''; |
| } |