Hand off presentation properly in VirtualDisplayController.resize() (flutter#17897)

GaryQian · web-flow · commit 0273fab7590b · 2020-04-23T15:32:20.000-07:00
diff --git a/shell/platform/android/io/flutter/plugin/platform/VirtualDisplayController.java b/shell/platform/android/io/flutter/plugin/platform/VirtualDisplayController.java
@@ -16,6 +16,7 @@
 import android.view.View;
 import android.view.ViewTreeObserver;
 import androidx.annotation.NonNull;
+import androidx.annotation.VisibleForTesting;
 import io.flutter.view.TextureRegistry;
 
 @TargetApi(Build.VERSION_CODES.KITKAT_WATCH)
@@ -62,7 +63,7 @@ public static VirtualDisplayController create(
   private final TextureRegistry.SurfaceTextureEntry textureEntry;
   private final OnFocusChangeListener focusChangeListener;
   private VirtualDisplay virtualDisplay;
-  private SingleViewPresentation presentation;
+  @VisibleForTesting SingleViewPresentation presentation;
   private Surface surface;
 
   private VirtualDisplayController(
@@ -145,15 +146,21 @@ public void run() {
           public void onViewDetachedFromWindow(View v) {}
         });
 
-    presentation =
+    // Create a new SingleViewPresentation and show() it before we cancel() the existing
+    // presentation. Calling show() and cancel() in this order fixes
+    // https://github.com/flutter/flutter/issues/26345 and maintains seamless transition
+    // of the contents of the presentation.
+    SingleViewPresentation newPresentation =
         new SingleViewPresentation(
             context,
             virtualDisplay.getDisplay(),
             accessibilityEventsDelegate,
             presentationState,
             focusChangeListener,
             isFocused);
-    presentation.show();
+    newPresentation.show();
+    presentation.cancel();
+    presentation = newPresentation;
   }
 
   public void dispose() {
diff --git a/shell/platform/android/test/io/flutter/plugin/platform/PlatformViewsControllerTest.java b/shell/platform/android/test/io/flutter/plugin/platform/PlatformViewsControllerTest.java
@@ -57,4 +57,26 @@ public void itNotifiesVirtualDisplayControllersOfViewAttachmentAndDetachment() {
     verify(fakeVdController2, times(1)).onFlutterViewAttached(eq(fakeFlutterView));
     verify(fakeVdController2, times(1)).onFlutterViewDetached();
   }
+
+  @Test
+  public void itCancelsOldPresentationOnResize() {
+    // Setup test structure.
+    // Create a fake View that represents the View that renders a Flutter UI.
+    View fakeFlutterView = new View(RuntimeEnvironment.systemContext);
+
+    // Create fake VirtualDisplayControllers. This requires internal knowledge of
+    // PlatformViewsController. We know that all PlatformViewsController does is
+    // forward view attachment/detachment calls to it's VirtualDisplayControllers.
+    //
+    // TODO(mattcarroll): once PlatformViewsController is refactored into testable
+    // pieces, remove this test and avoid verifying private behavior.
+    VirtualDisplayController fakeVdController1 = mock(VirtualDisplayController.class);
+
+    SingleViewPresentation presentation = fakeVdController1.presentation;
+
+    fakeVdController1.resize(10, 10, null);
+
+    assertEquals(fakeVdController1.presentation != presentation, true);
+    assertEquals(presentation.isShowing(), false);
+  }
 }
