[webview_flutter] Add listener for content offset

packages/webview_flutter/webview_flutter_android/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 3.4.5
+
+* Added `setOnContentOffsetChanged` method to the `AndroidWebViewController`.
+
 ## 3.4.4
 
 * Fixes a bug where the native `WebView` wouldn't be traversed for autofill automatically.

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

@@ -9,6 +9,7 @@
 import androidx.annotation.VisibleForTesting;
 import io.flutter.plugin.common.BinaryMessenger;
 import io.flutter.plugins.webviewflutter.GeneratedAndroidWebView.WebViewFlutterApi;
+import java.util.Objects;
 
 /**
  * Flutter API implementation for `WebView`.
@@ -56,4 +57,20 @@ public void create(@NonNull WebView instance, @NonNull WebViewFlutterApi.Reply<V
   void setApi(@NonNull WebViewFlutterApi api) {
     this.api = api;
   }
+
+  public void onScrollChanged(
+      @NonNull WebView instance,
+      @NonNull Long xArg,
+      @NonNull Long yArg,
+      @NonNull Long oldXArg,
+      @NonNull Long oldYArg,
+      WebViewFlutterApi.Reply<Void> callback) {
+    api.onScrollPosChange(
+        Objects.requireNonNull(instanceManager.getIdentifierForStrongReference(instance)),
+        xArg,
+        yArg,
+        oldXArg,
+        oldYArg,
+        callback);
+  }
 }

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

@@ -83,6 +83,7 @@ public void setWebContentsDebuggingEnabled(boolean enabled) {
   public static class WebViewPlatformView extends WebView implements PlatformView {
     private WebViewClient currentWebViewClient;
     private WebChromeClientHostApiImpl.SecureWebChromeClient currentWebChromeClient;
+    private final WebViewFlutterApiImpl webViewFlutterApi;
 
     /**
      * Creates a {@link WebViewPlatformView}.
@@ -94,7 +95,7 @@ public WebViewPlatformView(
       super(context);
       currentWebViewClient = new WebViewClient();
       currentWebChromeClient = new WebChromeClientHostApiImpl.SecureWebChromeClient();
-
+      webViewFlutterApi = new WebViewFlutterApiImpl(binaryMessenger, instanceManager);
       setWebViewClient(currentWebViewClient);
       setWebChromeClient(currentWebChromeClient);
     }
@@ -161,6 +162,13 @@ public void setWebChromeClient(WebChromeClient client) {
     public WebChromeClient getWebChromeClient() {
       return currentWebChromeClient;
     }
+
+    @Override
+    protected void onScrollChanged(int l, int t, int oldL, int oldT) {
+      super.onScrollChanged(l, t, oldL, oldT);
+      webViewFlutterApi.onScrollChanged(
+          this, (long) l, (long) t, (long) oldL, (long) oldT, reply -> {});
+    }
   }
 
   /**

packages/webview_flutter/webview_flutter_android/android/src/test/java/io/flutter/plugins/webviewflutter/WebViewTest.java

@@ -355,4 +355,25 @@ public void setImportantForAutofillForParentFlutterView() {
 
     verify(mockFlutterView).setImportantForAutofill(View.IMPORTANT_FOR_AUTOFILL_YES);
   }
+
+  @Test
+  public void onScrollPosChange() {
+    final InstanceManager instanceManager = InstanceManager.open(identifier -> {});
+
+    final WebViewFlutterApiImpl flutterApiImpl =
+        new WebViewFlutterApiImpl(mockBinaryMessenger, instanceManager);
+
+    final WebViewFlutterApi mockFlutterApi = mock(WebViewFlutterApi.class);
+    flutterApiImpl.setApi(mockFlutterApi);
+    flutterApiImpl.create(mockWebView, reply -> {});
+
+    flutterApiImpl.onScrollChanged(mockWebView, 0L, 1L, 2L, 3L, reply -> {});
+
+    final long instanceIdentifier =
+        Objects.requireNonNull(instanceManager.getIdentifierForStrongReference(mockWebView));
+    verify(mockFlutterApi)
+        .onScrollPosChange(eq(instanceIdentifier), eq(0L), eq(1L), eq(2L), eq(3L), any());
+
+    instanceManager.close();
+  }
 }

packages/webview_flutter/webview_flutter_android/example/android/build.gradle

@@ -24,7 +24,7 @@ subprojects {
     project.evaluationDependsOn(':app')
 }
 
-task clean(type: Delete) {
+tasks.register("clean", Delete) {
     delete rootProject.buildDir
 }
 

packages/webview_flutter/webview_flutter_android/example/integration_test/webview_flutter_test.dart

@@ -657,7 +657,8 @@ Future<void> main() async {
   });
 
   group('Programmatic Scroll', () {
-    testWidgets('setAndGetScrollPosition', (WidgetTester tester) async {
+    testWidgets('setAndGetAndListenScrollPosition',
+        (WidgetTester tester) async {
       const String scrollTestPage = '''
         <!DOCTYPE html>
         <html>
@@ -683,6 +684,7 @@ Future<void> main() async {
           base64Encode(const Utf8Encoder().convert(scrollTestPage));
 
       final Completer<void> pageLoaded = Completer<void>();
+      Completer<List<int>> offsetsCompleter = Completer<List<int>>();
       final PlatformWebViewController controller = PlatformWebViewController(
         const PlatformWebViewControllerCreationParams(),
       )
@@ -698,7 +700,11 @@ Future<void> main() async {
               'data:text/html;charset=utf-8;base64,$scrollTestPageBase64',
             ),
           ),
-        );
+        )
+        ..setOnContentOffsetChanged(
+            (int left, int top, int oldLeft, int oldTop) {
+          offsetsCompleter.complete(<int>[left, top, oldLeft, oldTop]);
+        });
 
       await tester.pumpWidget(Builder(
         builder: (BuildContext context) {
@@ -727,12 +733,17 @@ Future<void> main() async {
       scrollPos = await controller.getScrollPosition();
       expect(scrollPos.dx, X_SCROLL);
       expect(scrollPos.dy, Y_SCROLL);
+      expect(
+          offsetsCompleter.future, completion(<int>[X_SCROLL, Y_SCROLL, 0, 0]));
 
       // Check scrollBy() (on top of scrollTo())
+      offsetsCompleter = Completer<List<int>>();
       await controller.scrollBy(X_SCROLL, Y_SCROLL);
       scrollPos = await controller.getScrollPosition();
       expect(scrollPos.dx, X_SCROLL * 2);
       expect(scrollPos.dy, Y_SCROLL * 2);
+      expect(offsetsCompleter.future,
+          completion(<int>[X_SCROLL * 2, Y_SCROLL * 2, X_SCROLL, Y_SCROLL]));
     });
   });
 
@@ -1124,6 +1135,22 @@ Future<void> main() async {
       );
     },
   );
+
+  // testWidgets('On Content Offset Listener', (WidgetTester tester) async {
+  //   final PlatformWebViewController controller = PlatformWebViewController(
+  //     const PlatformWebViewControllerCreationParams(),
+  //   );
+  //   final Completer<List<int>> offsetCompleter = Completer<List<int>>();
+  //   controller.setOnContentOffsetChanged((left, top, oldLeft, oldTop) {
+  //     offsetCompleter.complete([left, top, oldLeft, oldTop]);
+  //   });
+  //
+  //   await tester.pumpWidget(widget);
+  //
+  //   await controller.runJavaScript('Echo.postMessage("hello");');
+  //   await expectLater(channelCompleter.future, completion('hello'));
+  //
+  // });
 }
 
 /// Returns the value used for the HTTP User-Agent: request header in subsequent HTTP requests.

packages/webview_flutter/webview_flutter_android/example/lib/main.dart

@@ -135,7 +135,11 @@ Page resource error:
       ))
       ..loadRequest(LoadRequestParams(
         uri: Uri.parse('https://flutter.dev'),
-      ));
+      ))
+      ..setOnContentOffsetChanged((int left, int top, int oldLeft, int oldTop) {
+        debugPrint(
+            'Scroll offset change to left = $left y = $top oldX = $oldLeft oldY = $oldTop');
+      });
   }
 
   @override

packages/webview_flutter/webview_flutter_android/example/pubspec.yaml

@@ -35,3 +35,9 @@ flutter:
     - assets/sample_video.mp4
     - assets/www/index.html
     - assets/www/styles/style.css
+
+
+# FOR TESTING ONLY. DO NOT MERGE.
+dependency_overrides:
+  webview_flutter_platform_interface:
+    path: ../../../webview_flutter/webview_flutter_platform_interface

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

@@ -29,9 +29,10 @@ class AndroidWebViewProxy {
   /// Due to changes in Flutter 3.0 the [useHybridComposition] doesn't have
   /// any effect and should not be exposed publicly. More info here:
   /// https://github.com/flutter/flutter/issues/108106
-  final android_webview.WebView Function({
-    required bool useHybridComposition,
-  }) createAndroidWebView;
+  final android_webview.WebView Function(
+      {required bool useHybridComposition,
+      required Function(int left, int top, int oldLeft, int oldTop)?
+          onScrollChanged}) createAndroidWebView;
 
   /// Constructs a [android_webview.WebChromeClient].
   final android_webview.WebChromeClient Function({

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

@@ -90,6 +90,7 @@ class WebView extends JavaObject {
   /// https://github.com/flutter/flutter/issues/108106
   WebView({
     this.useHybridComposition = false,
+    this.onScrollChanged,
     @visibleForTesting super.binaryMessenger,
     @visibleForTesting super.instanceManager,
   }) : super.detached() {
@@ -103,6 +104,7 @@ class WebView extends JavaObject {
   @protected
   WebView.detached({
     this.useHybridComposition = false,
+    this.onScrollChanged,
     super.binaryMessenger,
     super.instanceManager,
   }) : super.detached();
@@ -125,6 +127,9 @@ class WebView extends JavaObject {
   /// The [WebSettings] object used to control the settings for this WebView.
   late final WebSettings settings = WebSettings(this);
 
+  /// The [ScrollChangedCallback] object used to listen for scroll changed events.
+  final Function(int left, int top, int oldLeft, int oldTop)? onScrollChanged;
+
   /// Enables debugging of web contents (HTML / CSS / JavaScript) loaded into any WebViews of this application.
   ///
   /// This flag can be enabled in order to facilitate debugging of web layouts
@@ -414,6 +419,7 @@ class WebView extends JavaObject {
   WebView copy() {
     return WebView.detached(
       useHybridComposition: useHybridComposition,
+      onScrollChanged: onScrollChanged,
       binaryMessenger: _api.binaryMessenger,
       instanceManager: _api.instanceManager,
     );

packages/webview_flutter/webview_flutter_android/lib/src/android_webview.g.dart

@@ -1,7 +1,7 @@
 // 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.
-// Autogenerated from Pigeon (v9.0.4), do not edit directly.
+// Autogenerated from Pigeon (v9.1.4), do not edit directly.
 // See also: https://pub.dev/packages/pigeon
 // ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import
 
@@ -993,6 +993,9 @@ abstract class WebViewFlutterApi {
   /// Create a new Dart instance and add it to the `InstanceManager`.
   void create(int identifier);
 
+  void onScrollPosChange(
+      int webViewInstanceId, int x, int y, int oldX, int oldY);
+
   static void setup(WebViewFlutterApi? api,
       {BinaryMessenger? binaryMessenger}) {
     {
@@ -1014,6 +1017,38 @@ abstract class WebViewFlutterApi {
         });
       }
     }
+    {
+      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+          'dev.flutter.pigeon.WebViewFlutterApi.onScrollPosChange', codec,
+          binaryMessenger: binaryMessenger);
+      if (api == null) {
+        channel.setMessageHandler(null);
+      } else {
+        channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.WebViewFlutterApi.onScrollPosChange was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final int? arg_webViewInstanceId = (args[0] as int?);
+          assert(arg_webViewInstanceId != null,
+              'Argument for dev.flutter.pigeon.WebViewFlutterApi.onScrollPosChange was null, expected non-null int.');
+          final int? arg_x = (args[1] as int?);
+          assert(arg_x != null,
+              'Argument for dev.flutter.pigeon.WebViewFlutterApi.onScrollPosChange was null, expected non-null int.');
+          final int? arg_y = (args[2] as int?);
+          assert(arg_y != null,
+              'Argument for dev.flutter.pigeon.WebViewFlutterApi.onScrollPosChange was null, expected non-null int.');
+          final int? arg_oldX = (args[3] as int?);
+          assert(arg_oldX != null,
+              'Argument for dev.flutter.pigeon.WebViewFlutterApi.onScrollPosChange was null, expected non-null int.');
+          final int? arg_oldY = (args[4] as int?);
+          assert(arg_oldY != null,
+              'Argument for dev.flutter.pigeon.WebViewFlutterApi.onScrollPosChange was null, expected non-null int.');
+          api.onScrollPosChange(
+              arg_webViewInstanceId!, arg_x!, arg_y!, arg_oldX!, arg_oldY!);
+          return;
+        });
+      }
+    }
   }
 }
 

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

@@ -45,6 +45,7 @@ class AndroidWebViewFlutterApis {
     WebChromeClientFlutterApiImpl? webChromeClientFlutterApi,
     JavaScriptChannelFlutterApiImpl? javaScriptChannelFlutterApi,
     FileChooserParamsFlutterApiImpl? fileChooserParamsFlutterApi,
+    WebViewFlutterApiImpl? webViewFlutterApi,
   }) {
     this.javaObjectFlutterApi =
         javaObjectFlutterApi ?? JavaObjectFlutterApiImpl();
@@ -58,6 +59,7 @@ class AndroidWebViewFlutterApis {
         javaScriptChannelFlutterApi ?? JavaScriptChannelFlutterApiImpl();
     this.fileChooserParamsFlutterApi =
         fileChooserParamsFlutterApi ?? FileChooserParamsFlutterApiImpl();
+    this.webViewFlutterApi = webViewFlutterApi ?? WebViewFlutterApiImpl();
   }
 
   static bool _haveBeenSetUp = false;
@@ -85,6 +87,9 @@ class AndroidWebViewFlutterApis {
   /// Flutter Api for [FileChooserParams].
   late final FileChooserParamsFlutterApiImpl fileChooserParamsFlutterApi;
 
+  /// Flutter Api for [ScrollListener].
+  late final WebViewFlutterApiImpl webViewFlutterApi;
+
   /// Ensures all the Flutter APIs have been setup to receive calls from native code.
   void ensureSetUp() {
     if (!_haveBeenSetUp) {
@@ -94,6 +99,7 @@ class AndroidWebViewFlutterApis {
       WebChromeClientFlutterApi.setup(webChromeClientFlutterApi);
       JavaScriptChannelFlutterApi.setup(javaScriptChannelFlutterApi);
       FileChooserParamsFlutterApi.setup(fileChooserParamsFlutterApi);
+      WebViewFlutterApi.setup(webViewFlutterApi);
       _haveBeenSetUp = true;
     }
   }
@@ -371,6 +377,18 @@ class WebViewFlutterApiImpl implements WebViewFlutterApi {
   void create(int identifier) {
     instanceManager.addHostCreatedInstance(WebView.detached(), identifier);
   }
+
+  @override
+  void onScrollPosChange(
+      int webViewInstanceId, int x, int y, int oldX, int oldY) {
+    final WebView? webViewInstance = instanceManager
+        .getInstanceWithWeakReference(webViewInstanceId) as WebView?;
+    assert(
+      webViewInstance != null,
+      'InstanceManager does not contain a WebView with instanceId: $webViewInstanceId',
+    );
+    webViewInstance!.onScrollChanged!(x, y, oldX, oldY);
+  }
 }
 
 /// Host api implementation for [WebSettings].