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// Copyright 2018 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
import 'dart:async';
import 'package:flutter/foundation.dart';
import 'package:flutter/gestures.dart';
import 'package:flutter/widgets.dart';
import 'platform_interface.dart';
import 'src/webview_android.dart';
import 'src/webview_cupertino.dart';
/// Optional callback invoked when a web view is first created. [controller] is
/// the [WebViewController] for the created web view.
typedef void WebViewCreatedCallback(WebViewController controller);
/// Describes the state of JavaScript support in a given web view.
enum JavascriptMode {
/// JavaScript execution is disabled.
disabled,
/// JavaScript execution is not restricted.
unrestricted,
}
/// A message that was sent by JavaScript code running in a [WebView].
class JavascriptMessage {
/// Constructs a JavaScript message object.
///
/// The `message` parameter must not be null.
const JavascriptMessage(this.message) : assert(message != null);
/// The contents of the message that was sent by the JavaScript code.
final String message;
}
/// Callback type for handling messages sent from Javascript running in a web view.
typedef void JavascriptMessageHandler(JavascriptMessage message);
/// Information about a navigation action that is about to be executed.
class NavigationRequest {
NavigationRequest._({this.url, this.isForMainFrame});
/// The URL that will be loaded if the navigation is executed.
final String url;
/// Whether the navigation request is to be loaded as the main frame.
final bool isForMainFrame;
@override
String toString() {
return '$runtimeType(url: $url, isForMainFrame: $isForMainFrame)';
}
}
/// A decision on how to handle a navigation request.
enum NavigationDecision {
/// Prevent the navigation from taking place.
prevent,
/// Allow the navigation to take place.
navigate,
}
/// Decides how to handle a specific navigation request.
///
/// The returned [NavigationDecision] determines how the navigation described by
/// `navigation` should be handled.
///
/// See also: [WebView.navigationDelegate].
typedef FutureOr<NavigationDecision> NavigationDelegate(
NavigationRequest navigation);
/// Signature for when a [WebView] has started loading a page.
typedef void PageStartedCallback(String url);
/// Signature for when a [WebView] has finished loading a page.
typedef void PageFinishedCallback(String url);
/// Signature for when a [WebView] has failed to load a resource.
typedef void WebResourceErrorCallback(WebResourceError error);
/// Specifies possible restrictions on automatic media playback.
///
/// This is typically used in [WebView.initialMediaPlaybackPolicy].
// The method channel implementation is marshalling this enum to the value's index, so the order
// is important.
enum AutoMediaPlaybackPolicy {
/// Starting any kind of media playback requires a user action.
///
/// For example: JavaScript code cannot start playing media unless the code was executed
/// as a result of a user action (like a touch event).
require_user_action_for_all_media_types,
/// Starting any kind of media playback is always allowed.
///
/// For example: JavaScript code that's triggered when the page is loaded can start playing
/// video or audio.
always_allow,
}
final RegExp _validChannelNames = RegExp('^[a-zA-Z_][a-zA-Z0-9_]*\$');
/// A named channel for receiving messaged from JavaScript code running inside a web view.
class JavascriptChannel {
/// Constructs a Javascript channel.
///
/// The parameters `name` and `onMessageReceived` must not be null.
JavascriptChannel({
@required this.name,
@required this.onMessageReceived,
}) : assert(name != null),
assert(onMessageReceived != null),
assert(_validChannelNames.hasMatch(name));
/// The channel's name.
///
/// Passing this channel object as part of a [WebView.javascriptChannels] adds a channel object to
/// the Javascript window object's property named `name`.
///
/// The name must start with a letter or underscore(_), followed by any combination of those
/// characters plus digits.
///
/// Note that any JavaScript existing `window` property with this name will be overriden.
///
/// See also [WebView.javascriptChannels] for more details on the channel registration mechanism.
final String name;
/// A callback that's invoked when a message is received through the channel.
final JavascriptMessageHandler onMessageReceived;
}
/// A web view widget for showing html content.
class WebView extends StatefulWidget {
/// Creates a new web view.
///
/// The web view can be controlled using a `WebViewController` that is passed to the
/// `onWebViewCreated` callback once the web view is created.
///
/// The `javascriptMode` and `autoMediaPlaybackPolicy` parameters must not be null.
const WebView({
Key key,
this.onWebViewCreated,
this.initialUrl,
this.javascriptMode = JavascriptMode.disabled,
this.javascriptChannels,
this.navigationDelegate,
this.gestureRecognizers,
this.onPageStarted,
this.onPageFinished,
this.onWebResourceError,
this.debuggingEnabled = false,
this.gestureNavigationEnabled = false,
this.userAgent,
this.initialMediaPlaybackPolicy =
AutoMediaPlaybackPolicy.require_user_action_for_all_media_types,
}) : assert(javascriptMode != null),
assert(initialMediaPlaybackPolicy != null),
super(key: key);
static WebViewPlatform _platform;
/// Sets a custom [WebViewPlatform].
///
/// This property can be set to use a custom platform implementation for WebViews.
///
/// Setting `platform` doesn't affect [WebView]s that were already created.
///
/// The default value is [AndroidWebView] on Android and [CupertinoWebView] on iOS.
static set platform(WebViewPlatform platform) {
_platform = platform;
}
/// The WebView platform that's used by this WebView.
///
/// The default value is [AndroidWebView] on Android and [CupertinoWebView] on iOS.
static WebViewPlatform get platform {
if (_platform == null) {
switch (defaultTargetPlatform) {
case TargetPlatform.android:
_platform = AndroidWebView();
break;
case TargetPlatform.iOS:
_platform = CupertinoWebView();
break;
default:
throw UnsupportedError(
"Trying to use the default webview implementation for $defaultTargetPlatform but there isn't a default one");
}
}
return _platform;
}
/// If not null invoked once the web view is created.
final WebViewCreatedCallback onWebViewCreated;
/// Which gestures should be consumed by the web view.
///
/// It is possible for other gesture recognizers to be competing with the web view on pointer
/// events, e.g if the web view is inside a [ListView] the [ListView] will want to handle
/// vertical drags. The web view will claim gestures that are recognized by any of the
/// recognizers on this list.
///
/// When this set is empty or null, the web view will only handle pointer events for gestures that
/// were not claimed by any other gesture recognizer.
final Set<Factory<OneSequenceGestureRecognizer>> gestureRecognizers;
/// The initial URL to load.
final String initialUrl;
/// Whether Javascript execution is enabled.
final JavascriptMode javascriptMode;
/// The set of [JavascriptChannel]s available to JavaScript code running in the web view.
///
/// For each [JavascriptChannel] in the set, a channel object is made available for the
/// JavaScript code in a window property named [JavascriptChannel.name].
/// The JavaScript code can then call `postMessage` on that object to send a message that will be
/// passed to [JavascriptChannel.onMessageReceived].
///
/// For example for the following JavascriptChannel:
///
/// ```dart
/// JavascriptChannel(name: 'Print', onMessageReceived: (JavascriptMessage message) { print(message.message); });
/// ```
///
/// JavaScript code can call:
///
/// ```javascript
/// Print.postMessage('Hello');
/// ```
///
/// To asynchronously invoke the message handler which will print the message to standard output.
///
/// Adding a new JavaScript channel only takes affect after the next page is loaded.
///
/// Set values must not be null. A [JavascriptChannel.name] cannot be the same for multiple
/// channels in the list.
///
/// A null value is equivalent to an empty set.
final Set<JavascriptChannel> javascriptChannels;
/// A delegate function that decides how to handle navigation actions.
///
/// When a navigation is initiated by the WebView (e.g when a user clicks a link)
/// this delegate is called and has to decide how to proceed with the navigation.
///
/// See [NavigationDecision] for possible decisions the delegate can take.
///
/// When null all navigation actions are allowed.
///
/// Caveats on Android:
///
/// * Navigation actions targeted to the main frame can be intercepted,
/// navigation actions targeted to subframes are allowed regardless of the value
/// returned by this delegate.
/// * Setting a navigationDelegate makes the WebView treat all navigations as if they were
/// triggered by a user gesture, this disables some of Chromium's security mechanisms.
/// A navigationDelegate should only be set when loading trusted content.
/// * On Android WebView versions earlier than 67(most devices running at least Android L+ should have
/// a later version):
/// * When a navigationDelegate is set pages with frames are not properly handled by the
/// webview, and frames will be opened in the main frame.
/// * When a navigationDelegate is set HTTP requests do not include the HTTP referer header.
final NavigationDelegate navigationDelegate;
/// Invoked when a page starts loading.
final PageStartedCallback onPageStarted;
/// Invoked when a page has finished loading.
///
/// This is invoked only for the main frame.
///
/// When [onPageFinished] is invoked on Android, the page being rendered may
/// not be updated yet.
///
/// When invoked on iOS or Android, any Javascript code that is embedded
/// directly in the HTML has been loaded and code injected with
/// [WebViewController.evaluateJavascript] can assume this.
final PageFinishedCallback onPageFinished;
/// Invoked when a web resource has failed to load.
///
/// This can be called for any resource (iframe, image, etc.), not just for
/// the main page.
final WebResourceErrorCallback onWebResourceError;
/// Controls whether WebView debugging is enabled.
///
/// Setting this to true enables [WebView debugging on Android](https://developers.google.com/web/tools/chrome-devtools/remote-debugging/).
///
/// WebView debugging is enabled by default in dev builds on iOS.
///
/// To debug WebViews on iOS:
/// - Enable developer options (Open Safari, go to Preferences -> Advanced and make sure "Show Develop Menu in Menubar" is on.)
/// - From the Menu-bar (of Safari) select Develop -> iPhone Simulator -> <your webview page>
///
/// By default `debuggingEnabled` is false.
final bool debuggingEnabled;
/// A Boolean value indicating whether horizontal swipe gestures will trigger back-forward list navigations.
///
/// This only works on iOS.
///
/// By default `gestureNavigationEnabled` is false.
final bool gestureNavigationEnabled;
/// The value used for the HTTP User-Agent: request header.
///
/// When null the platform's webview default is used for the User-Agent header.
///
/// When the [WebView] is rebuilt with a different `userAgent`, the page reloads and the request uses the new User Agent.
///
/// When [WebViewController.goBack] is called after changing `userAgent` the previous `userAgent` value is used until the page is reloaded.
///
/// This field is ignored on iOS versions prior to 9 as the platform does not support a custom
/// user agent.
///
/// By default `userAgent` is null.
final String userAgent;
/// Which restrictions apply on automatic media playback.
///
/// This initial value is applied to the platform's webview upon creation. Any following
/// changes to this parameter are ignored (as long as the state of the [WebView] is preserved).
///
/// The default policy is [AutoMediaPlaybackPolicy.require_user_action_for_all_media_types].
final AutoMediaPlaybackPolicy initialMediaPlaybackPolicy;
@override
State<StatefulWidget> createState() => _WebViewState();
}
class _WebViewState extends State<WebView> {
final Completer<WebViewController> _controller =
Completer<WebViewController>();
_PlatformCallbacksHandler _platformCallbacksHandler;
@override
Widget build(BuildContext context) {
return WebView.platform.build(
context: context,
onWebViewPlatformCreated: _onWebViewPlatformCreated,
webViewPlatformCallbacksHandler: _platformCallbacksHandler,
gestureRecognizers: widget.gestureRecognizers,
creationParams: _creationParamsfromWidget(widget),
);
}
@override
void initState() {
super.initState();
_assertJavascriptChannelNamesAreUnique();
_platformCallbacksHandler = _PlatformCallbacksHandler(widget);
}
@override
void didUpdateWidget(WebView oldWidget) {
super.didUpdateWidget(oldWidget);
_assertJavascriptChannelNamesAreUnique();
_controller.future.then((WebViewController controller) {
_platformCallbacksHandler._widget = widget;
controller._updateWidget(widget);
});
}
void _onWebViewPlatformCreated(WebViewPlatformController webViewPlatform) {
final WebViewController controller =
WebViewController._(widget, webViewPlatform, _platformCallbacksHandler);
_controller.complete(controller);
if (widget.onWebViewCreated != null) {
widget.onWebViewCreated(controller);
}
}
void _assertJavascriptChannelNamesAreUnique() {
if (widget.javascriptChannels == null ||
widget.javascriptChannels.isEmpty) {
return;
}
assert(_extractChannelNames(widget.javascriptChannels).length ==
widget.javascriptChannels.length);
}
}
CreationParams _creationParamsfromWidget(WebView widget) {
return CreationParams(
initialUrl: widget.initialUrl,
webSettings: _webSettingsFromWidget(widget),
javascriptChannelNames: _extractChannelNames(widget.javascriptChannels),
userAgent: widget.userAgent,
autoMediaPlaybackPolicy: widget.initialMediaPlaybackPolicy,
);
}
WebSettings _webSettingsFromWidget(WebView widget) {
return WebSettings(
javascriptMode: widget.javascriptMode,
hasNavigationDelegate: widget.navigationDelegate != null,
debuggingEnabled: widget.debuggingEnabled,
gestureNavigationEnabled: widget.gestureNavigationEnabled,
userAgent: WebSetting<String>.of(widget.userAgent),
);
}
// This method assumes that no fields in `currentValue` are null.
WebSettings _clearUnchangedWebSettings(
WebSettings currentValue, WebSettings newValue) {
assert(currentValue.javascriptMode != null);
assert(currentValue.hasNavigationDelegate != null);
assert(currentValue.debuggingEnabled != null);
assert(currentValue.userAgent.isPresent);
assert(newValue.javascriptMode != null);
assert(newValue.hasNavigationDelegate != null);
assert(newValue.debuggingEnabled != null);
assert(newValue.userAgent.isPresent);
JavascriptMode javascriptMode;
bool hasNavigationDelegate;
bool debuggingEnabled;
WebSetting<String> userAgent = WebSetting<String>.absent();
if (currentValue.javascriptMode != newValue.javascriptMode) {
javascriptMode = newValue.javascriptMode;
}
if (currentValue.hasNavigationDelegate != newValue.hasNavigationDelegate) {
hasNavigationDelegate = newValue.hasNavigationDelegate;
}
if (currentValue.debuggingEnabled != newValue.debuggingEnabled) {
debuggingEnabled = newValue.debuggingEnabled;
}
if (currentValue.userAgent != newValue.userAgent) {
userAgent = newValue.userAgent;
}
return WebSettings(
javascriptMode: javascriptMode,
hasNavigationDelegate: hasNavigationDelegate,
debuggingEnabled: debuggingEnabled,
userAgent: userAgent,
);
}
Set<String> _extractChannelNames(Set<JavascriptChannel> channels) {
final Set<String> channelNames = channels == null
// TODO(iskakaushik): Remove this when collection literals makes it to stable.
// ignore: prefer_collection_literals
? Set<String>()
: channels.map((JavascriptChannel channel) => channel.name).toSet();
return channelNames;
}
class _PlatformCallbacksHandler implements WebViewPlatformCallbacksHandler {
_PlatformCallbacksHandler(this._widget) {
_updateJavascriptChannelsFromSet(_widget.javascriptChannels);
}
WebView _widget;
// Maps a channel name to a channel.
final Map<String, JavascriptChannel> _javascriptChannels =
<String, JavascriptChannel>{};
@override
void onJavaScriptChannelMessage(String channel, String message) {
_javascriptChannels[channel].onMessageReceived(JavascriptMessage(message));
}
@override
FutureOr<bool> onNavigationRequest({String url, bool isForMainFrame}) async {
final NavigationRequest request =
NavigationRequest._(url: url, isForMainFrame: isForMainFrame);
final bool allowNavigation = _widget.navigationDelegate == null ||
await _widget.navigationDelegate(request) ==
NavigationDecision.navigate;
return allowNavigation;
}
@override
void onPageStarted(String url) {
if (_widget.onPageStarted != null) {
_widget.onPageStarted(url);
}
}
@override
void onPageFinished(String url) {
if (_widget.onPageFinished != null) {
_widget.onPageFinished(url);
}
}
@override
void onWebResourceError(WebResourceError error) {
if (_widget.onWebResourceError != null) {
_widget.onWebResourceError(error);
}
}
void _updateJavascriptChannelsFromSet(Set<JavascriptChannel> channels) {
_javascriptChannels.clear();
if (channels == null) {
return;
}
for (JavascriptChannel channel in channels) {
_javascriptChannels[channel.name] = channel;
}
}
}
/// Controls a [WebView].
///
/// A [WebViewController] instance can be obtained by setting the [WebView.onWebViewCreated]
/// callback for a [WebView] widget.
class WebViewController {
WebViewController._(
this._widget,
this._webViewPlatformController,
this._platformCallbacksHandler,
) : assert(_webViewPlatformController != null) {
_settings = _webSettingsFromWidget(_widget);
}
final WebViewPlatformController _webViewPlatformController;
final _PlatformCallbacksHandler _platformCallbacksHandler;
WebSettings _settings;
WebView _widget;
/// Loads the specified URL.
///
/// If `headers` is not null and the URL is an HTTP URL, the key value paris in `headers` will
/// be added as key value pairs of HTTP headers for the request.
///
/// `url` must not be null.
///
/// Throws an ArgumentError if `url` is not a valid URL string.
Future<void> loadUrl(
String url, {
Map<String, String> headers,
}) async {
assert(url != null);
_validateUrlString(url);
return _webViewPlatformController.loadUrl(url, headers);
}
/// Accessor to the current URL that the WebView is displaying.
///
/// If [WebView.initialUrl] was never specified, returns `null`.
/// Note that this operation is asynchronous, and it is possible that the
/// current URL changes again by the time this function returns (in other
/// words, by the time this future completes, the WebView may be displaying a
/// different URL).
Future<String> currentUrl() {
return _webViewPlatformController.currentUrl();
}
/// Checks whether there's a back history item.
///
/// Note that this operation is asynchronous, and it is possible that the "canGoBack" state has
/// changed by the time the future completed.
Future<bool> canGoBack() {
return _webViewPlatformController.canGoBack();
}
/// Checks whether there's a forward history item.
///
/// Note that this operation is asynchronous, and it is possible that the "canGoForward" state has
/// changed by the time the future completed.
Future<bool> canGoForward() {
return _webViewPlatformController.canGoForward();
}
/// Goes back in the history of this WebView.
///
/// If there is no back history item this is a no-op.
Future<void> goBack() {
return _webViewPlatformController.goBack();
}
/// Goes forward in the history of this WebView.
///
/// If there is no forward history item this is a no-op.
Future<void> goForward() {
return _webViewPlatformController.goForward();
}
/// Reloads the current URL.
Future<void> reload() {
return _webViewPlatformController.reload();
}
/// Clears all caches used by the [WebView].
///
/// The following caches are cleared:
/// 1. Browser HTTP Cache.
/// 2. [Cache API](https://developers.google.com/web/fundamentals/instant-and-offline/web-storage/cache-api) caches.
/// These are not yet supported in iOS WkWebView. Service workers tend to use this cache.
/// 3. Application cache.
/// 4. Local Storage.
///
/// Note: Calling this method also triggers a reload.
Future<void> clearCache() async {
await _webViewPlatformController.clearCache();
return reload();
}
Future<void> _updateWidget(WebView widget) async {
_widget = widget;
await _updateSettings(_webSettingsFromWidget(widget));
await _updateJavascriptChannels(widget.javascriptChannels);
}
Future<void> _updateSettings(WebSettings newSettings) {
final WebSettings update =
_clearUnchangedWebSettings(_settings, newSettings);
_settings = newSettings;
return _webViewPlatformController.updateSettings(update);
}
Future<void> _updateJavascriptChannels(
Set<JavascriptChannel> newChannels) async {
final Set<String> currentChannels =
_platformCallbacksHandler._javascriptChannels.keys.toSet();
final Set<String> newChannelNames = _extractChannelNames(newChannels);
final Set<String> channelsToAdd =
newChannelNames.difference(currentChannels);
final Set<String> channelsToRemove =
currentChannels.difference(newChannelNames);
if (channelsToRemove.isNotEmpty) {
await _webViewPlatformController
.removeJavascriptChannels(channelsToRemove);
}
if (channelsToAdd.isNotEmpty) {
await _webViewPlatformController.addJavascriptChannels(channelsToAdd);
}
_platformCallbacksHandler._updateJavascriptChannelsFromSet(newChannels);
}
/// Evaluates a JavaScript expression in the context of the current page.
///
/// On Android returns the evaluation result as a JSON formatted string.
///
/// On iOS depending on the value type the return value would be one of:
///
/// - For primitive JavaScript types: the value string formatted (e.g JavaScript 100 returns '100').
/// - For JavaScript arrays of supported types: a string formatted NSArray(e.g '(1,2,3), note that the string for NSArray is formatted and might contain newlines and extra spaces.').
/// - Other non-primitive types are not supported on iOS and will complete the Future with an error.
///
/// The Future completes with an error if a JavaScript error occurred, or on iOS, if the type of the
/// evaluated expression is not supported as described above.
///
/// When evaluating Javascript in a [WebView], it is best practice to wait for
/// the [WebView.onPageFinished] callback. This guarantees all the Javascript
/// embedded in the main frame HTML has been loaded.
Future<String> evaluateJavascript(String javascriptString) {
if (_settings.javascriptMode == JavascriptMode.disabled) {
return Future<String>.error(FlutterError(
'JavaScript mode must be enabled/unrestricted when calling evaluateJavascript.'));
}
if (javascriptString == null) {
return Future<String>.error(
ArgumentError('The argument javascriptString must not be null.'));
}
// TODO(amirh): remove this on when the invokeMethod update makes it to stable Flutter.
// https://github.com/flutter/flutter/issues/26431
// ignore: strong_mode_implicit_dynamic_method
return _webViewPlatformController.evaluateJavascript(javascriptString);
}
/// Returns the title of the currently loaded page.
Future<String> getTitle() {
return _webViewPlatformController.getTitle();
}
}
/// Manages cookies pertaining to all [WebView]s.
class CookieManager {
/// Creates a [CookieManager] -- returns the instance if it's already been called.
factory CookieManager() {
return _instance ??= CookieManager._();
}
CookieManager._();
static CookieManager _instance;
/// Clears all cookies for all [WebView] instances.
///
/// This is a no op on iOS version smaller than 9.
///
/// Returns true if cookies were present before clearing, else false.
Future<bool> clearCookies() => WebView.platform.clearCookies();
}
// Throws an ArgumentError if `url` is not a valid URL string.
void _validateUrlString(String url) {
try {
final Uri uri = Uri.parse(url);
if (uri.scheme.isEmpty) {
throw ArgumentError('Missing scheme in URL string: "$url"');
}
} on FormatException catch (e) {
throw ArgumentError(e);
}
}