[webview_flutter_wkwebview] Add WKWebView method stubs (#4990)

Author: bparrishMines

packages/webview_flutter/webview_flutter_wkwebview/lib/src/ui_kit/ui_kit.dart

@@ -0,0 +1,38 @@
+// Copyright 2013 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.
+
+import 'dart:async';
+import 'dart:math';
+
+import '../web_kit/web_kit.dart';
+
+/// A view that allows the scrolling and zooming of its contained views.
+///
+/// Wraps [UIScrollView](https://developer.apple.com/documentation/uikit/uiscrollview?language=objc).
+class UIScrollView {
+  /// Constructs a [UIScrollView] that is owned by [webView].
+  // TODO(bparrishMines): Remove ignore once constructor is implemented.
+  // ignore: avoid_unused_constructor_parameters
+  UIScrollView.fromWebView(WKWebView webView);
+
+  /// Point at which the origin of the content view is offset from the origin of the scroll view.
+  Future<Point<double>> get contentOffset {
+    throw UnimplementedError();
+  }
+
+  /// Move the scrolled position of this view.
+  ///
+  /// This method is not a part of UIKit and is only a helper method to make
+  /// scrollBy atomic.
+  Future<void> scrollBy(Point<double> offset) {
+    throw UnimplementedError();
+  }
+
+  /// Set point at which the origin of the content view is offset from the origin of the scroll view.
+  ///
+  /// The default value is `Point<double>(0.0, 0.0)`.
+  set contentOffset(FutureOr<Point<double>> offset) {
+    throw UnimplementedError();
+  }
+}

packages/webview_flutter/webview_flutter_wkwebview/lib/src/web_kit/web_kit.dart

@@ -5,6 +5,7 @@
 import 'package:flutter/foundation.dart';
 
 import '../foundation/foundation.dart';
+import '../ui_kit/ui_kit.dart';
 
 /// Times at which to inject script content into a webpage.
 ///
@@ -450,6 +451,9 @@ class WKWebView {
   late final WKWebViewConfiguration configuration =
       WKWebViewConfiguration._fromWebView(this);
 
+  /// The scrollable view associated with the web view.
+  late final UIScrollView scrollView = UIScrollView.fromWebView(this);
+
   /// Used to integrate custom user interface elements into web view interactions.
   set uiDelegate(WKUIDelegate? delegate) {
     throw UnimplementedError();
@@ -472,4 +476,79 @@ class WKWebView {
   Future<void> loadRequest(NSUrlRequest request) {
     throw UnimplementedError();
   }
+
+  /// Loads the contents of the specified HTML string and navigates to it.
+  Future<void> loadHtmlString(String string, {String? baseUrl}) {
+    throw UnimplementedError();
+  }
+
+  /// Loads the web content from the specified file and navigates to it.
+  Future<void> loadFileUrl(String url, {required String readAccessUrl}) {
+    throw UnimplementedError();
+  }
+
+  /// Loads the Flutter asset specified in the pubspec.yaml file.
+  ///
+  /// This method is not a part of WebKit and is only a Flutter specific helper
+  /// method.
+  Future<void> loadFlutterAsset(String key) {
+    throw UnimplementedError();
+  }
+
+  /// Indicates whether there is a valid back item in the back-forward list.
+  Future<bool> get canGoBack {
+    throw UnimplementedError();
+  }
+
+  /// Indicates whether there is a valid forward item in the back-forward list.
+  Future<bool> get canGoForward {
+    throw UnimplementedError();
+  }
+
+  /// Navigates to the back item in the back-forward list.
+  Future<void> goBack() {
+    throw UnimplementedError();
+  }
+
+  /// Navigates to the forward item in the back-forward list.
+  Future<void> goForward() {
+    throw UnimplementedError();
+  }
+
+  /// Reloads the current webpage.
+  Future<void> reload() {
+    throw UnimplementedError();
+  }
+
+  /// The page title.
+  Future<String?> get title {
+    throw UnimplementedError();
+  }
+
+  /// An estimate of what fraction of the current navigation has been loaded.
+  Future<double> get estimatedProgress {
+    throw UnimplementedError();
+  }
+
+  /// Indicates whether horizontal swipe gestures trigger page navigation.
+  ///
+  /// The default value is false.
+  set allowsBackForwardNavigationGestures(bool allow) {
+    throw UnimplementedError();
+  }
+
+  /// The custom user agent string.
+  ///
+  /// The default value of this property is null.
+  set customUserAgent(String? userAgent) {
+    throw UnimplementedError();
+  }
+
+  /// Evaluates the specified JavaScript string.
+  ///
+  /// Throws a `PlatformException` if an error occurs or return value is not
+  /// supported.
+  Future<Object?> evaluateJavaScript(String javaScriptString) {
+    throw UnimplementedError();
+  }
 }

packages/webview_flutter/webview_flutter_wkwebview/lib/src/web_kit_webview_widget.dart

@@ -3,9 +3,12 @@
 // found in the LICENSE file.
 
 import 'dart:async';
+import 'dart:math';
 
 import 'package:flutter/foundation.dart';
+import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
+import 'package:path/path.dart' as path;
 import 'package:webview_flutter_platform_interface/webview_flutter_platform_interface.dart';
 
 import 'foundation/foundation.dart';
@@ -194,6 +197,19 @@ class WebKitWebViewPlatformController extends WebViewPlatformController {
     };
   }
 
+  @override
+  Future<void> loadHtmlString(String html, {String? baseUrl}) {
+    return webView.loadHtmlString(html, baseUrl: baseUrl);
+  }
+
+  @override
+  Future<void> loadFile(String absoluteFilePath) async {
+    await webView.loadFileUrl(
+      absoluteFilePath,
+      readAccessUrl: path.dirname(absoluteFilePath),
+    );
+  }
+
   @override
   Future<void> clearCache() {
     return webView.configuration.webSiteDataStore.removeDataOfTypes(
@@ -207,6 +223,124 @@ class WebKitWebViewPlatformController extends WebViewPlatformController {
     );
   }
 
+  @override
+  Future<void> loadFlutterAsset(String key) async {
+    assert(key.isNotEmpty);
+    return webView.loadFlutterAsset(key);
+  }
+
+  @override
+  Future<void> loadUrl(String url, Map<String, String>? headers) async {
+    final NSUrlRequest request = NSUrlRequest(
+      url: url,
+      allHttpHeaderFields: headers ?? <String, String>{},
+    );
+    return webView.loadRequest(request);
+  }
+
+  @override
+  Future<void> loadRequest(WebViewRequest request) async {
+    if (!request.uri.hasScheme) {
+      throw ArgumentError('WebViewRequest#uri is required to have a scheme.');
+    }
+
+    final NSUrlRequest urlRequest = NSUrlRequest(
+      url: request.uri.toString(),
+      allHttpHeaderFields: request.headers,
+      httpMethod: describeEnum(request.method),
+      httpBody: request.body,
+    );
+
+    return webView.loadRequest(urlRequest);
+  }
+
+  @override
+  Future<bool> canGoBack() => webView.canGoBack;
+
+  @override
+  Future<bool> canGoForward() => webView.canGoForward;
+
+  @override
+  Future<void> goBack() => webView.goBack();
+
+  @override
+  Future<void> goForward() => webView.goForward();
+
+  @override
+  Future<void> reload() => webView.reload();
+
+  @override
+  Future<String> evaluateJavascript(String javascript) async {
+    final Object? result = await webView.evaluateJavaScript(javascript);
+    // The legacy implementation of webview_flutter_wkwebview would convert
+    // objects to strings before returning them to Dart. This method attempts
+    // to converts Dart objects to Strings the way it is done in Objective-C
+    // to avoid breaking users expecting the same String format.
+    return _asObjectiveCString(result);
+  }
+
+  @override
+  Future<void> runJavascript(String javascript) async {
+    try {
+      await webView.evaluateJavaScript(javascript);
+    } on PlatformException catch (exception) {
+      // WebKit will throw an error when the type of the evaluated value is
+      // unsupported. This also goes for `null` and `undefined` on iOS 14+. For
+      // example, when running a void function. For ease of use, this specific
+      // error is ignored when no return value is expected.
+      // TODO(bparrishMines): Ensure the platform code includes the NSError in
+      // the FlutterError.details.
+      if (exception.details is! NSError ||
+          exception.details.code !=
+              WKErrorCode.javaScriptResultTypeIsUnsupported) {
+        rethrow;
+      }
+    }
+  }
+
+  @override
+  Future<String> runJavascriptReturningResult(String javascript) async {
+    final Object? result = await webView.evaluateJavaScript(javascript);
+    if (result == null) {
+      throw ArgumentError(
+        'Result of JavaScript execution returned a `null` value. '
+        'Use `runJavascript` when expecting a null return value.',
+      );
+    }
+    return result.toString();
+  }
+
+  @override
+  Future<String?> getTitle() => webView.title;
+
+  @override
+  Future<void> scrollTo(int x, int y) async {
+    webView.scrollView.contentOffset = Point<double>(
+      x.toDouble(),
+      y.toDouble(),
+    );
+  }
+
+  @override
+  Future<void> scrollBy(int x, int y) async {
+    await webView.scrollView.scrollBy(Point<double>(
+      x.toDouble(),
+      y.toDouble(),
+    ));
+  }
+
+  @override
+  Future<int> getScrollX() async {
+    final Point<double> offset = await webView.scrollView.contentOffset;
+    return offset.x.toInt();
+  }
+
+  @override
+  Future<int> getScrollY() async {
+    final Point<double> offset = await webView.scrollView.contentOffset;
+    return offset.y.toInt();
+  }
+
   @override
   Future<void> updateSettings(WebSettings setting) async {
     if (setting.hasNavigationDelegate != null) {
@@ -324,6 +458,35 @@ class WebKitWebViewPlatformController extends WebViewPlatformController {
       errorType: errorType,
     );
   }
+
+  String _asObjectiveCString(Object? value, {bool inContainer = false}) {
+    if (value == null) {
+      // An NSNull inside an NSArray or NSDictionary is represented as a String
+      // differently than a nil.
+      if (inContainer) {
+        return '"<null>"';
+      }
+      return '(null)';
+    } else if (value is List) {
+      final List<String> stringValues = <String>[];
+      for (final Object? listValue in value) {
+        stringValues.add(_asObjectiveCString(listValue, inContainer: true));
+      }
+      return '(${stringValues.join(',')})';
+    } else if (value is Map) {
+      final List<String> stringValues = <String>[];
+      for (final MapEntry<Object?, Object?> entry in value.entries) {
+        stringValues.add(
+          '${_asObjectiveCString(entry.key, inContainer: true)} '
+          '= '
+          '${_asObjectiveCString(entry.value, inContainer: true)}',
+        );
+      }
+      return '{${stringValues.join(';')}}';
+    }
+
+    return value.toString();
+  }
 }
 
 /// Handles constructing objects and calling static methods.

packages/webview_flutter/webview_flutter_wkwebview/pubspec.yaml

@@ -18,6 +18,7 @@ flutter:
 dependencies:
   flutter:
     sdk: flutter
+  path: ^1.8.0
   webview_flutter_platform_interface: ^1.8.0
 
 dev_dependencies: