Fix memory leak in PlatformViewsController

Author: Emmanuel Garcia

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

@@ -79,7 +79,7 @@ public class PlatformViewsController implements PlatformViewsAccessibilityDelega
   // Since each virtual display has it's unique context this allows associating any view with the
   // platform view that
   // it is associated with(e.g if a platform view creates other views in the same virtual display.
-  private final HashMap<Context, View> contextToPlatformView;
+  @VisibleForTesting /* package */ final HashMap<Context, View> contextToPlatformView;
 
   // The views returned by `PlatformView#getView()`.
   //
@@ -711,6 +711,10 @@ private void flushAllViews() {
     while (platformViews.size() > 0) {
       channelHandler.disposeAndroidViewForPlatformView(platformViews.keyAt(0));
     }
+
+    if (contextToPlatformView.size() > 0) {
+      contextToPlatformView.clear();
+    }
   }
 
   private void initializeRootImageViewIfNeeded() {

shell/platform/android/test/io/flutter/plugin/platform/PlatformViewsControllerTest.java

@@ -291,6 +291,56 @@ public void createPlatformViewMessage__throwsIfViewIsNull() {
         });
   }
 
+  @Test
+  @Config(shadows = {ShadowFlutterJNI.class})
+  public void onDetachedFromJNI_clearsPlatformViewContext() {
+    PlatformViewsController platformViewsController = new PlatformViewsController();
+
+    int platformViewId = 0;
+    assertNull(platformViewsController.getPlatformViewById(platformViewId));
+
+    PlatformViewFactory viewFactory = mock(PlatformViewFactory.class);
+    PlatformView platformView = mock(PlatformView.class);
+    when(platformView.getView()).thenReturn(null);
+    when(viewFactory.create(any(), eq(platformViewId), any())).thenReturn(platformView);
+    platformViewsController.getRegistry().registerViewFactory("testType", viewFactory);
+
+    FlutterJNI jni = new FlutterJNI();
+    attach(jni, platformViewsController);
+
+    // Simulate create call from the framework.
+    createPlatformView(jni, platformViewsController, platformViewId, "testType");
+
+    assertFalse(platformViewsController.contextToPlatformView.isEmpty());
+    platformViewsController.onDetachedFromJNI();
+    assertTrue(platformViewsController.contextToPlatformView.isEmpty());
+  }
+
+  @Test
+  @Config(shadows = {ShadowFlutterJNI.class})
+  public void onPreEngineRestart_clearsPlatformViewContext() {
+    PlatformViewsController platformViewsController = new PlatformViewsController();
+
+    int platformViewId = 0;
+    assertNull(platformViewsController.getPlatformViewById(platformViewId));
+
+    PlatformViewFactory viewFactory = mock(PlatformViewFactory.class);
+    PlatformView platformView = mock(PlatformView.class);
+    when(platformView.getView()).thenReturn(null);
+    when(viewFactory.create(any(), eq(platformViewId), any())).thenReturn(platformView);
+    platformViewsController.getRegistry().registerViewFactory("testType", viewFactory);
+
+    FlutterJNI jni = new FlutterJNI();
+    attach(jni, platformViewsController);
+
+    // Simulate create call from the framework.
+    createPlatformView(jni, platformViewsController, platformViewId, "testType");
+
+    assertFalse(platformViewsController.contextToPlatformView.isEmpty());
+    platformViewsController.onDetachedFromJNI();
+    assertTrue(platformViewsController.contextToPlatformView.isEmpty());
+  }
+
   @Test
   @Config(shadows = {ShadowFlutterJNI.class})
   public void createPlatformViewMessage__throwsIfViewHasParent() {