Notify PlatformViewsController within FlutterEngine when a hot restart occurs. (#48518)

Author: matthew-carroll

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

@@ -112,6 +112,8 @@ public void onPreEngineRestart() {
       for (EngineLifecycleListener lifecycleListener : engineLifecycleListeners) {
         lifecycleListener.onPreEngineRestart();
       }
+
+      platformViewsController.onPreEngineRestart();
     }
   };
 
@@ -190,6 +192,27 @@ public FlutterEngine(
       @NonNull FlutterJNI flutterJNI,
       @Nullable String[] dartVmArgs,
       boolean automaticallyRegisterPlugins
+  ) {
+    this(
+        context,
+        flutterLoader,
+        flutterJNI,
+        new PlatformViewsController(),
+        dartVmArgs,
+        automaticallyRegisterPlugins
+    );
+  }
+
+  /**
+   * Fully configurable {@code FlutterEngine} constructor.
+   */
+  public FlutterEngine(
+      @NonNull Context context,
+      @NonNull FlutterLoader flutterLoader,
+      @NonNull FlutterJNI flutterJNI,
+      @NonNull PlatformViewsController platformViewsController,
+      @Nullable String[] dartVmArgs,
+      boolean automaticallyRegisterPlugins
   ) {
     this.flutterJNI = flutterJNI;
     flutterLoader.startInitialization(context);
@@ -214,7 +237,7 @@ public FlutterEngine(
     systemChannel = new SystemChannel(dartExecutor);
     textInputChannel = new TextInputChannel(dartExecutor);
 
-    platformViewsController = new PlatformViewsController();
+    this.platformViewsController = platformViewsController;
 
     this.pluginRegistry = new FlutterEnginePluginRegistry(
       context.getApplicationContext(),

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

@@ -1,11 +1,13 @@
 package test.io.flutter.embedding.engine;
 
+import io.flutter.plugin.platform.PlatformViewsController;
 import io.flutter.plugins.GeneratedPluginRegistrant;
 import java.util.List;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
+import org.mockito.ArgumentCaptor;
 import org.mockito.Mock;
 import org.mockito.MockitoAnnotations;
 import org.robolectric.RobolectricTestRunner;
@@ -17,8 +19,11 @@
 import io.flutter.embedding.engine.loader.FlutterLoader;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertTrue;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
 @Config(manifest=Config.NONE)
@@ -64,4 +69,37 @@ public void itCanBeConfiguredToNotAutomaticallyRegisterPlugins() {
 
     assertTrue(GeneratedPluginRegistrant.getRegisteredEngines().isEmpty());
   }
+
+  @Test
+  public void itNotifiesPlatformViewsControllerWhenDevHotRestart() {
+    // Setup test.
+    FlutterJNI mockFlutterJNI = mock(FlutterJNI.class);
+    when(mockFlutterJNI.isAttached()).thenReturn(true);
+
+    PlatformViewsController platformViewsController = mock(PlatformViewsController.class);
+
+    ArgumentCaptor<FlutterEngine.EngineLifecycleListener> engineLifecycleListenerArgumentCaptor = ArgumentCaptor.forClass(FlutterEngine.EngineLifecycleListener.class);
+
+    // Execute behavior under test.
+    new FlutterEngine(
+        RuntimeEnvironment.application,
+        mock(FlutterLoader.class),
+        mockFlutterJNI,
+        platformViewsController,
+        /*dartVmArgs=*/new String[] {},
+        /*automaticallyRegisterPlugins=*/false
+    );
+
+    // Obtain the EngineLifecycleListener within FlutterEngine that was given to FlutterJNI.
+    verify(mockFlutterJNI).addEngineLifecycleListener(engineLifecycleListenerArgumentCaptor.capture());
+    FlutterEngine.EngineLifecycleListener engineLifecycleListener = engineLifecycleListenerArgumentCaptor.getValue();
+    assertNotNull(engineLifecycleListener);
+
+    // Simulate a pre-engine restart, AKA hot restart.
+    engineLifecycleListener.onPreEngineRestart();
+
+    // Verify that FlutterEngine notified PlatformViewsController of the pre-engine restart,
+    // AKA hot restart.
+    verify(platformViewsController, times(1)).onPreEngineRestart();
+  }
 }