[webview_flutter_android][webview_flutter_wkwebview] Adds support to retrieve native WebView (#7071)

* implementation of the webViewIdentifier field

* change to external classes

* formatting

* update readmes

* iOS

* improve

* hmmmm

* add note about not using other apis

* project changes

* add external api tests to project

* ordering

* fix docs and use id

Author: bparrishMines

packages/webview_flutter/webview_flutter_android/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 3.3.0
+
+* Adds support to access native `WebView`.
+
 ## 3.2.4
 
 * Renames Pigeon output files.

packages/webview_flutter/webview_flutter_android/README.md

@@ -32,6 +32,22 @@ This can be configured for versions >=23 with
 `AndroidWebViewWidgetCreationParams.displayWithHybridComposition`. See https://pub.dev/packages/webview_flutter#platform-specific-features
 for more details on setting platform-specific features in the main plugin.
 
+### External Native API
+
+The plugin also provides a native API accessible by the native code of Android applications or
+packages. This API follows the convention of breaking changes of the Dart API, which means that any
+changes to the class that are not backwards compatible will only be made with a major version change
+of the plugin. Native code other than this external API does not follow breaking change conventions,
+so app or plugin clients should not use any other native APIs.
+
+The API can be accessed by importing the native class `WebViewFlutterAndroidExternalApi`:
+
+Java:
+
+```java
+import io.flutter.plugins.webviewflutter.WebViewFlutterAndroidExternalApi;
+```
+
 ## Contributing
 
 This package uses [pigeon][3] to generate the communication layer between Flutter and the host

packages/webview_flutter/webview_flutter_android/android/src/main/java/io/flutter/plugins/webviewflutter/WebViewFlutterAndroidExternalApi.java

@@ -0,0 +1,50 @@
+// 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.
+
+package io.flutter.plugins.webviewflutter;
+
+import android.webkit.WebView;
+import androidx.annotation.Nullable;
+import io.flutter.embedding.engine.FlutterEngine;
+
+/**
+ * App and package facing native API provided by the `webview_flutter_android` plugin.
+ *
+ * <p>This class follows the convention of breaking changes of the Dart API, which means that any
+ * changes to the class that are not backwards compatible will only be made with a major version
+ * change of the plugin.
+ *
+ * <p>Native code other than this external API does not follow breaking change conventions, so app
+ * or plugin clients should not use any other native APIs.
+ */
+@SuppressWarnings("unused")
+public interface WebViewFlutterAndroidExternalApi {
+  /**
+   * Retrieves the {@link WebView} that is associated with `identifier`.
+   *
+   * <p>See the Dart method `AndroidWebViewController.webViewIdentifier` to get the identifier of an
+   * underlying `WebView`.
+   *
+   * @param engine the execution environment the {@link WebViewFlutterPlugin} should belong to. If
+   *     the engine doesn't contain an attached instance of {@link WebViewFlutterPlugin}, this
+   *     method returns null.
+   * @param identifier the associated identifier of the `WebView`.
+   * @return the `WebView` associated with `identifier` or null if a `WebView` instance associated
+   *     with `identifier` could not be found.
+   */
+  @Nullable
+  static WebView getWebView(FlutterEngine engine, long identifier) {
+    final WebViewFlutterPlugin webViewPlugin =
+        (WebViewFlutterPlugin) engine.getPlugins().get(WebViewFlutterPlugin.class);
+
+    if (webViewPlugin != null && webViewPlugin.getInstanceManager() != null) {
+      final Object instance = webViewPlugin.getInstanceManager().getInstance(identifier);
+      if (instance instanceof WebView) {
+        return (WebView) instance;
+      }
+    }
+
+    return null;
+  }
+}

packages/webview_flutter/webview_flutter_android/android/src/main/java/io/flutter/plugins/webviewflutter/WebViewFlutterPlugin.java

@@ -33,7 +33,7 @@
  * <p>Call {@link #registerWith} to use the stable {@code io.flutter.plugin.common} package instead.
  */
 public class WebViewFlutterPlugin implements FlutterPlugin, ActivityAware {
-  private InstanceManager instanceManager;
+  @Nullable private InstanceManager instanceManager;
 
   private FlutterPluginBinding pluginBinding;
   private WebViewHostApiImpl webViewHostApi;
@@ -148,7 +148,10 @@ public void onAttachedToEngine(@NonNull FlutterPluginBinding binding) {
 
   @Override
   public void onDetachedFromEngine(@NonNull FlutterPluginBinding binding) {
-    instanceManager.close();
+    if (instanceManager != null) {
+      instanceManager.close();
+      instanceManager = null;
+    }
   }
 
   @Override

packages/webview_flutter/webview_flutter_android/android/src/test/java/io/flutter/plugins/webviewflutter/WebViewFlutterPluginTest.java renamed to packages/webview_flutter/webview_flutter_android/android/src/test/java/io/flutter/plugins/webviewflutter/WebViewFlutterAndroidExternalApiTest.java

@@ -4,11 +4,16 @@
 
 package io.flutter.plugins.webviewflutter;
 
+import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
+import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 
 import android.content.Context;
+import android.webkit.WebView;
+import io.flutter.embedding.engine.FlutterEngine;
 import io.flutter.embedding.engine.plugins.FlutterPlugin;
+import io.flutter.embedding.engine.plugins.PluginRegistry;
 import io.flutter.plugin.common.BinaryMessenger;
 import io.flutter.plugin.platform.PlatformViewRegistry;
 import org.junit.Rule;
@@ -17,7 +22,7 @@
 import org.mockito.junit.MockitoJUnit;
 import org.mockito.junit.MockitoRule;
 
-public class WebViewFlutterPluginTest {
+public class WebViewFlutterAndroidExternalApiTest {
   @Rule public MockitoRule mockitoRule = MockitoJUnit.rule();
 
   @Mock Context mockContext;
@@ -29,7 +34,7 @@ public class WebViewFlutterPluginTest {
   @Mock FlutterPlugin.FlutterPluginBinding mockPluginBinding;
 
   @Test
-  public void getInstanceManagerAfterOnAttachedToEngine() {
+  public void getWebView() {
     final WebViewFlutterPlugin webViewFlutterPlugin = new WebViewFlutterPlugin();
 
     when(mockPluginBinding.getApplicationContext()).thenReturn(mockContext);
@@ -38,7 +43,19 @@ public void getInstanceManagerAfterOnAttachedToEngine() {
 
     webViewFlutterPlugin.onAttachedToEngine(mockPluginBinding);
 
-    assertNotNull(webViewFlutterPlugin.getInstanceManager());
+    final InstanceManager instanceManager = webViewFlutterPlugin.getInstanceManager();
+    assertNotNull(instanceManager);
+
+    final WebView mockWebView = mock(WebView.class);
+    instanceManager.addDartCreatedInstance(mockWebView, 0);
+
+    final PluginRegistry mockPluginRegistry = mock(PluginRegistry.class);
+    when(mockPluginRegistry.get(WebViewFlutterPlugin.class)).thenReturn(webViewFlutterPlugin);
+
+    final FlutterEngine mockFlutterEngine = mock(FlutterEngine.class);
+    when(mockFlutterEngine.getPlugins()).thenReturn(mockPluginRegistry);
+
+    assertEquals(WebViewFlutterAndroidExternalApi.getWebView(mockFlutterEngine, 0), mockWebView);
 
     webViewFlutterPlugin.onDetachedFromEngine(mockPluginBinding);
   }

packages/webview_flutter/webview_flutter_android/lib/src/android_webview_controller.dart

@@ -144,6 +144,16 @@ class AndroidWebViewController extends PlatformWebViewController {
     return webViewProxy.setWebContentsDebuggingEnabled(enabled);
   }
 
+  /// Identifier used to retrieve the underlying native `WKWebView`.
+  ///
+  /// This is typically used by other plugins to retrieve the native `WebView`
+  /// from an `InstanceManager`.
+  ///
+  /// See Java method `WebViewFlutterPlugin.getWebView`.
+  int get webViewIdentifier =>
+      // ignore: invalid_use_of_visible_for_testing_member
+      android_webview.WebView.api.instanceManager.getIdentifier(_webView)!;
+
   @override
   Future<void> loadFile(
     String absoluteFilePath,

packages/webview_flutter/webview_flutter_android/pubspec.yaml

@@ -2,7 +2,7 @@ name: webview_flutter_android
 description: A Flutter plugin that provides a WebView widget on Android.
 repository: https://github.com/flutter/plugins/tree/main/packages/webview_flutter/webview_flutter_android
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+webview%22
-version: 3.2.4
+version: 3.3.0
 
 environment:
   sdk: ">=2.17.0 <3.0.0"

packages/webview_flutter/webview_flutter_android/test/android_webview_controller_test.dart

@@ -14,6 +14,7 @@ import 'package:mockito/mockito.dart';
 import 'package:webview_flutter_android/src/android_proxy.dart';
 import 'package:webview_flutter_android/src/android_webview.dart'
     as android_webview;
+import 'package:webview_flutter_android/src/android_webview_api_impls.dart';
 import 'package:webview_flutter_android/src/instance_manager.dart';
 import 'package:webview_flutter_android/src/platform_views_service_proxy.dart';
 import 'package:webview_flutter_android/webview_flutter_android.dart';
@@ -884,6 +885,29 @@ void main() {
     verify(mockSettings.setMediaPlaybackRequiresUserGesture(true)).called(1);
   });
 
+  test('webViewIdentifier', () {
+    final MockWebView mockWebView = MockWebView();
+    final InstanceManager instanceManager = InstanceManager(
+      onWeakReferenceRemoved: (_) {},
+    );
+    instanceManager.addHostCreatedInstance(mockWebView, 0);
+
+    android_webview.WebView.api = WebViewHostApiImpl(
+      instanceManager: instanceManager,
+    );
+
+    final AndroidWebViewController controller = createControllerWithMocks(
+      mockWebView: mockWebView,
+    );
+
+    expect(
+      controller.webViewIdentifier,
+      0,
+    );
+
+    android_webview.WebView.api = WebViewHostApiImpl();
+  });
+
   group('AndroidWebViewWidget', () {
     testWidgets('Builds Android view using supplied parameters',
         (WidgetTester tester) async {

packages/webview_flutter/webview_flutter_wkwebview/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 3.1.0
+
+* Adds support to access native `WKWebView`.
+
 ## 3.0.5
 
 * Renames Pigeon output files.

packages/webview_flutter/webview_flutter_wkwebview/README.md

@@ -7,6 +7,24 @@ The Apple WKWebView implementation of [`webview_flutter`][1].
 This package is [endorsed][2], which means you can simply use `webview_flutter`
 normally. This package will be automatically included in your app when you do.
 
+### External Native API
+
+The plugin also provides a native API accessible by the native code of iOS applications or packages.
+This API follows the convention of breaking changes of the Dart API, which means that any changes to
+the class that are not backwards compatible will only be made with a major version change of the
+plugin. Native code other than this external API does not follow breaking change conventions, so
+app or plugin clients should not use any other native APIs.
+
+The API can be accessed by importing the native plugin `webview_flutter_wkwebview`:
+
+Objective-C:
+
+```objectivec
+@import webview_flutter_wkwebview;
+```
+
+Then you will have access to the native class `FWFWebViewFlutterWKWebViewExternalAPI`.
+
 ## Contributing
 
 This package uses [pigeon][3] to generate the communication layer between Flutter and the host