[android] Fix black and blank screen issues on the platform view page.

shell/platform/android/io/flutter/embedding/android/FlutterView.java

@@ -86,7 +86,7 @@ public class FlutterView extends FrameLayout implements MouseCursorPlugin.MouseC
   @Nullable private FlutterSurfaceView flutterSurfaceView;
   @Nullable private FlutterTextureView flutterTextureView;
   @Nullable private FlutterImageView flutterImageView;
-  @Nullable private RenderSurface renderSurface;
+  @Nullable @VisibleForTesting /* package */ RenderSurface renderSurface;
   @Nullable private RenderSurface previousRenderSurface;
   private final Set<FlutterUiDisplayListener> flutterUiDisplayListeners = new HashSet<>();
   private boolean isFlutterUiDisplayed;
@@ -1083,6 +1083,11 @@ public void detachFromFlutterEngine() {
     flutterRenderer.removeIsDisplayingFlutterUiListener(flutterUiDisplayListener);
     flutterRenderer.stopRenderingToSurface();
     flutterRenderer.setSemanticsEnabled(false);
+
+    // Revert the image view to previous surface
+    if (previousRenderSurface != null && renderSurface == flutterImageView) {
+      renderSurface = previousRenderSurface;
+    }
     renderSurface.detachFromRenderer();
 
     flutterImageView = null;

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

@@ -503,6 +503,7 @@ public void attachToView(@NonNull View flutterView) {
   public void detachFromView() {
     destroyOverlaySurfaces();
     this.flutterView = null;
+    flutterViewConvertedToImageView = false;
 
     // Inform all existing platform views that they are no longer associated with
     // a Flutter View.

shell/platform/android/test/io/flutter/embedding/android/FlutterViewTest.java

@@ -108,6 +108,22 @@ public void detachFromFlutterEngine_turnsOffA11y() {
     verify(flutterRenderer, times(1)).setSemanticsEnabled(false);
   }
 
+  @Test
+  public void detachFromFlutterEngine_revertImageView() {
+    FlutterView flutterView = new FlutterView(RuntimeEnvironment.application);
+    FlutterEngine flutterEngine =
+        spy(new FlutterEngine(RuntimeEnvironment.application, mockFlutterLoader, mockFlutterJni));
+
+    flutterView.attachToFlutterEngine(flutterEngine);
+    assertFalse(flutterView.renderSurface instanceof FlutterImageView);
+
+    flutterView.convertToImageView();
+    assertTrue(flutterView.renderSurface instanceof FlutterImageView);
+
+    flutterView.detachFromFlutterEngine();
+    assertFalse(flutterView.renderSurface instanceof FlutterImageView);
+  }
+
   @Test
   public void onConfigurationChanged_fizzlesWhenNullEngine() {
     FlutterView flutterView = new FlutterView(RuntimeEnvironment.application);