onBeginFrame JNI (flutter#18866)

Author: cg021

shell/platform/android/io/flutter/embedding/engine/FlutterJNI.java

@@ -799,6 +799,17 @@ public void onDisplayOverlaySurface(int id, int x, int y, int width, int height)
     }
     platformViewsController.onDisplayOverlaySurface(id, x, y, width, height);
   }
+
+  @SuppressWarnings("unused")
+  @UiThread
+  public void onBeginFrame() {
+    ensureRunningOnMainThread();
+    if (platformViewsController == null) {
+      throw new RuntimeException(
+          "platformViewsController must be set before attempting to begin the frame");
+    }
+    platformViewsController.onBeginFrame();
+  }
   // ----- End Engine Lifecycle Support ----
 
   // @SuppressWarnings("unused")

shell/platform/android/io/flutter/plugin/platform/PlatformViewsController.java

@@ -541,4 +541,8 @@ public void onDisplayPlatformView(int viewId, int x, int y, int width, int heigh
   public void onDisplayOverlaySurface(int id, int x, int y, int width, int height) {
     // TODO: Implement this method. https://github.com/flutter/flutter/issues/58288
   }
+
+  public void onBeginFrame() {
+    // TODO: Implement this method. https://github.com/flutter/flutter/issues/58288
+  }
 }

shell/platform/android/jni/platform_view_android_jni.h

@@ -130,6 +130,13 @@ class PlatformViewAndroidJNI {
                                                 int y,
                                                 int width,
                                                 int height) = 0;
+  //----------------------------------------------------------------------------
+  /// @brief      Initiates a frame if using hybrid composition.
+  ///
+  ///
+  /// @note       Must be called from the platform thread.
+  ///
+  virtual void FlutterViewBeginFrame() = 0;
 };
 
 }  // namespace flutter

shell/platform/android/platform_view_android_jni_impl.cc

@@ -80,6 +80,8 @@ static jmethodID g_on_first_frame_method = nullptr;
 
 static jmethodID g_on_engine_restart_method = nullptr;
 
+static jmethodID g_on_begin_frame_method = nullptr;
+
 static jmethodID g_attach_to_gl_context_method = nullptr;
 
 static jmethodID g_update_tex_image_method = nullptr;
@@ -718,6 +720,14 @@ bool PlatformViewAndroid::Register(JNIEnv* env) {
     return false;
   }
 
+  g_on_begin_frame_method =
+      env->GetMethodID(g_flutter_jni_class->obj(), "onBeginFrame", "()V");
+
+  if (g_on_begin_frame_method == nullptr) {
+    FML_LOG(ERROR) << "Could not locate onBeginFrame method";
+    return false;
+  }
+
   g_on_display_overlay_surface_method = env->GetMethodID(
       g_flutter_jni_class->obj(), "onDisplayOverlaySurface", "(IIIII)V");
 
@@ -1034,4 +1044,17 @@ void PlatformViewAndroidJNIImpl::FlutterViewDisplayOverlaySurface(
   FML_CHECK(CheckException(env));
 }
 
+void PlatformViewAndroidJNIImpl::FlutterViewBeginFrame() {
+  JNIEnv* env = fml::jni::AttachCurrentThread();
+
+  auto java_object = java_object_.get(env);
+  if (java_object.is_null()) {
+    return;
+  }
+
+  env->CallVoidMethod(java_object.obj(), g_on_begin_frame_method);
+
+  FML_CHECK(CheckException(env));
+}
+
 }  // namespace flutter

shell/platform/android/platform_view_android_jni_impl.h

@@ -62,6 +62,8 @@ class PlatformViewAndroidJNIImpl final : public PlatformViewAndroidJNI {
                                         int width,
                                         int height) override;
 
+  void FlutterViewBeginFrame() override;
+
  private:
   // Reference to FlutterJNI object.
   const fml::jni::JavaObjectWeakGlobalRef java_object_;

shell/platform/android/test/io/flutter/embedding/engine/FlutterJNITest.java

@@ -81,4 +81,19 @@ public void onDisplayOverlaySurface__callsPlatformViewsController() {
     verify(platformViewsController, times(1))
         .onDisplayOverlaySurface(/*id=*/ 1, /*x=*/ 10, /*y=*/ 20, /*width=*/ 100, /*height=*/ 200);
   }
+
+  @Test
+  public void onBeginFrame__callsPlatformViewsController() {
+    PlatformViewsController platformViewsController = mock(PlatformViewsController.class);
+
+    // --- Test Setup ---
+    FlutterJNI flutterJNI = new FlutterJNI();
+    flutterJNI.setPlatformViewsController(platformViewsController);
+
+    // --- Execute Test ---
+    flutterJNI.onBeginFrame();
+
+    // --- Verify Results ---
+    verify(platformViewsController, times(1)).onBeginFrame();
+  }
 }