[webview_flutter_android][webview_flutter_wkwebview] Adds support for setOnScrollPositionChange for webview_flutter platform implementations (#5664)

Adds iOS and Android implementation for content offset listener

This PR is part of a series of PRs that aim to close flutter/flutter#31027.

The PR that contains all changes can be found at #3444.

Author: TheVinhLuong

packages/webview_flutter/webview_flutter_android/AUTHORS

@@ -67,4 +67,5 @@ Rahul Raj <64.rahulraj@gmail.com>
 Maurits van Beusekom <maurits@baseflow.com>
 Nick Bradshaw <nickalasb@gmail.com>
 Kai Yu <yk3372@gmail.com>
+The Vinh Luong <ltv.luongthevinh@gmail.com>
 

packages/webview_flutter/webview_flutter_android/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 3.15.0
+
+* Adds support for `setOnScrollPositionChange` method to the `AndroidWebViewController`.
+
 ## 3.14.0
 
 * Adds support to show JavaScript dialog. See `AndroidWebViewController.setOnJavaScriptAlertDialog`, `AndroidWebViewController.setOnJavaScriptConfirmDialog` and `AndroidWebViewController.setOnJavaScriptTextInputDialog`.

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

@@ -1758,6 +1758,24 @@ public void create(@NonNull Long identifierArg, @NonNull Reply<Void> callback) {
           new ArrayList<Object>(Collections.singletonList(identifierArg)),
           channelReply -> callback.reply(null));
     }
+
+    public void onScrollChanged(
+        @NonNull Long webViewInstanceIdArg,
+        @NonNull Long leftArg,
+        @NonNull Long topArg,
+        @NonNull Long oldLeftArg,
+        @NonNull Long oldTopArg,
+        @NonNull Reply<Void> callback) {
+      BasicMessageChannel<Object> channel =
+          new BasicMessageChannel<>(
+              binaryMessenger,
+              "dev.flutter.pigeon.webview_flutter_android.WebViewFlutterApi.onScrollChanged",
+              getCodec());
+      channel.send(
+          new ArrayList<Object>(
+              Arrays.asList(webViewInstanceIdArg, leftArg, topArg, oldLeftArg, oldTopArg)),
+          channelReply -> callback.reply(null));
+    }
   }
   /** Generated interface from Pigeon that represents a handler of messages from Flutter. */
   public interface WebSettingsHostApi {

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 left,
+      @NonNull Long top,
+      @NonNull Long oldLeft,
+      @NonNull Long oldTop,
+      @NonNull WebViewFlutterApi.Reply<Void> callback) {
+    api.onScrollChanged(
+        Objects.requireNonNull(instanceManager.getIdentifierForStrongReference(instance)),
+        left,
+        top,
+        oldLeft,
+        oldTop,
+        callback);
+  }
 }

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

@@ -180,6 +180,13 @@ public WebChromeClient getWebChromeClient() {
       return currentWebChromeClient;
     }
 
+    @Override
+    protected void onScrollChanged(int left, int top, int oldLeft, int oldTop) {
+      super.onScrollChanged(left, top, oldLeft, oldTop);
+      api.onScrollChanged(
+          this, (long) left, (long) top, (long) oldLeft, (long) oldTop, reply -> {});
+    }
+
     /**
      * Flutter API used to send messages back to Dart.
      *

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

@@ -358,4 +358,25 @@ public void setImportantForAutofillForParentFlutterView() {
 
     verify(mockFlutterView).setImportantForAutofill(View.IMPORTANT_FOR_AUTOFILL_YES);
   }
+
+  @Test
+  public void onScrollChanged() {
+    final InstanceManager instanceManager = InstanceManager.create(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)
+        .onScrollChanged(eq(instanceIdentifier), eq(0L), eq(1L), eq(2L), eq(3L), any());
+
+    instanceManager.stopFinalizationListener();
+  }
 }

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

@@ -758,7 +758,8 @@ Future<void> main() async {
   });
 
   group('Programmatic Scroll', () {
-    testWidgets('setAndGetScrollPosition', (WidgetTester tester) async {
+    testWidgets('setAndGetAndListenScrollPosition',
+        (WidgetTester tester) async {
       const String scrollTestPage = '''
         <!DOCTYPE html>
         <html>
@@ -784,6 +785,7 @@ Future<void> main() async {
           base64Encode(const Utf8Encoder().convert(scrollTestPage));
 
       final Completer<void> pageLoaded = Completer<void>();
+      ScrollPositionChange? recordedPosition;
       final PlatformWebViewController controller = PlatformWebViewController(
         const PlatformWebViewControllerCreationParams(),
       );
@@ -793,6 +795,10 @@ Future<void> main() async {
       );
       unawaited(delegate.setOnPageFinished((_) => pageLoaded.complete()));
       unawaited(controller.setPlatformNavigationDelegate(delegate));
+      unawaited(controller.setOnScrollPositionChange(
+          (ScrollPositionChange contentOffsetChange) {
+        recordedPosition = contentOffsetChange;
+      }));
 
       await controller.loadRequest(
         LoadRequestParams(
@@ -824,17 +830,22 @@ Future<void> main() async {
       // time to settle.
       expect(scrollPos.dx, isNot(X_SCROLL));
       expect(scrollPos.dy, isNot(Y_SCROLL));
+      expect(recordedPosition, null);
 
       await controller.scrollTo(X_SCROLL, Y_SCROLL);
       scrollPos = await controller.getScrollPosition();
       expect(scrollPos.dx, X_SCROLL);
       expect(scrollPos.dy, Y_SCROLL);
+      expect(recordedPosition?.x, X_SCROLL);
+      expect(recordedPosition?.y, Y_SCROLL);
 
       // Check scrollBy() (on top of scrollTo())
       await controller.scrollBy(X_SCROLL, Y_SCROLL);
       scrollPos = await controller.getScrollPosition();
       expect(scrollPos.dx, X_SCROLL * 2);
       expect(scrollPos.dy, Y_SCROLL * 2);
+      expect(recordedPosition?.x, X_SCROLL * 2);
+      expect(recordedPosition?.y, Y_SCROLL * 2);
     });
   });
 

packages/webview_flutter/webview_flutter_android/example/pubspec.yaml

@@ -17,7 +17,7 @@ dependencies:
     # The example app is bundled with the plugin so we use a path dependency on
     # the parent directory to use the current plugin's version.
     path: ../
-  webview_flutter_platform_interface: ^2.9.0
+  webview_flutter_platform_interface: ^2.10.0
 
 dev_dependencies:
   espresso: ^0.2.0

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

@@ -25,7 +25,9 @@ class AndroidWebViewProxy {
   });
 
   /// Constructs a [android_webview.WebView].
-  final android_webview.WebView Function() createAndroidWebView;
+  final android_webview.WebView Function({
+    void 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

@@ -132,11 +132,8 @@ class GeolocationPermissionsCallback extends JavaObject {
 /// When a [WebView] is no longer needed [release] must be called.
 class WebView extends View {
   /// Constructs a new WebView.
-  ///
-  /// 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
   WebView({
+    this.onScrollChanged,
     @visibleForTesting super.binaryMessenger,
     @visibleForTesting super.instanceManager,
   }) : super.detached() {
@@ -149,6 +146,7 @@ class WebView extends View {
   /// create copies.
   @protected
   WebView.detached({
+    this.onScrollChanged,
     super.binaryMessenger,
     super.instanceManager,
   }) : super.detached();
@@ -160,6 +158,18 @@ class WebView extends View {
   /// The [WebSettings] object used to control the settings for this WebView.
   late final WebSettings settings = WebSettings(this);
 
+  /// Called in response to an internal scroll in this view
+  /// (i.e., the view scrolled its own contents).
+  ///
+  /// This is typically as a result of [scrollBy] or [scrollTo]
+  /// having been called.
+  final void 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
@@ -448,6 +458,7 @@ class WebView extends View {
   @override
   WebView copy() {
     return WebView.detached(
+      onScrollChanged: onScrollChanged,
       binaryMessenger: _api.binaryMessenger,
       instanceManager: _api.instanceManager,
     );