Wait before switching surfaces (flutter#20100)

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

@@ -953,13 +953,22 @@ public void detachFromFlutterEngine() {
     flutterEngine = null;
   }
 
+  @VisibleForTesting
+  @NonNull
+  public FlutterImageView createImageView() {
+    return new FlutterImageView(
+        getContext(), getWidth(), getHeight(), FlutterImageView.SurfaceKind.background);
+  }
+
+  /**
+   * Converts the current render surface to a {@link FlutterImageView} if it's not one already.
+   * Otherwise, it resizes the {@link FlutterImageView} based on the current view size.
+   */
   public void convertToImageView() {
     renderSurface.pause();
 
     if (flutterImageView == null) {
-      flutterImageView =
-          new FlutterImageView(
-              getContext(), getWidth(), getHeight(), FlutterImageView.SurfaceKind.background);
+      flutterImageView = createImageView();
       addView(flutterImageView);
     } else {
       flutterImageView.resizeIfNeeded(getWidth(), getHeight());
@@ -973,10 +982,13 @@ public void convertToImageView() {
   }
 
   /**
-   * If the surface is rendered by a {@code FlutterImageView}. Then, calling this method will stop
-   * rendering to a {@code FlutterImageView}, and use the previous surface instead.
+   * If the surface is rendered by a {@link FlutterImageView}, then calling this method will stop
+   * rendering to a {@link FlutterImageView}, and render on the previous surface instead.
+   *
+   * @param onDone a callback called when Flutter UI is rendered on the previous surface. Use this
+   *     callback to perform cleanups. For example, destroy overlay surfaces.
    */
-  public void revertImageView() {
+  public void revertImageView(@NonNull Runnable onDone) {
     if (flutterImageView == null) {
       Log.v(TAG, "Tried to revert the image view, but no image view is used.");
       return;
@@ -985,12 +997,39 @@ public void revertImageView() {
       Log.v(TAG, "Tried to revert the image view, but no previous surface was used.");
       return;
     }
-    flutterImageView.detachFromRenderer();
     renderSurface = previousRenderSurface;
     previousRenderSurface = null;
-    if (flutterEngine != null) {
-      renderSurface.attachToRenderer(flutterEngine.getRenderer());
+    if (flutterEngine == null) {
+      flutterImageView.detachFromRenderer();
+      onDone.run();
+      return;
+    }
+    final FlutterRenderer renderer = flutterEngine.getRenderer();
+    if (renderer == null) {
+      flutterImageView.detachFromRenderer();
+      onDone.run();
+      return;
     }
+    // Start rendering on the previous surface.
+    // This surface is typically `FlutterSurfaceView` or `FlutterTextureView`.
+    renderSurface.attachToRenderer(renderer);
+
+    // Install a Flutter UI listener to wait until the first frame is rendered
+    // in the new surface to call the `onDone` callback.
+    renderer.addIsDisplayingFlutterUiListener(
+        new FlutterUiDisplayListener() {
+          @Override
+          public void onFlutterUiDisplayed() {
+            renderer.removeIsDisplayingFlutterUiListener(this);
+            onDone.run();
+            flutterImageView.detachFromRenderer();
+          }
+
+          @Override
+          public void onFlutterUiNoLongerDisplayed() {
+            // no-op
+          }
+        });
   }
 
   public void attachOverlaySurfaceToRender(FlutterImageView view) {

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

@@ -90,7 +90,7 @@
  *
  * <p>To invoke a native method that is not associated with a platform view, invoke it statically:
  *
- * <p>{@code bool enabled = FlutterJNI.nativeGetIsSoftwareRenderingEnabled(); }
+ * <p>{@code bool enabled = FlutterJNI.getIsSoftwareRenderingEnabled(); }
  */
 @Keep
 public class FlutterJNI {
@@ -120,9 +120,13 @@ public static native void nativeInit(
    */
   public static native void nativePrefetchDefaultFontManager();
 
-  // TODO(mattcarroll): add javadocs
+  private native boolean nativeGetIsSoftwareRenderingEnabled();
+
   @UiThread
-  public native boolean nativeGetIsSoftwareRenderingEnabled();
+  // TODO(mattcarroll): add javadocs
+  public boolean getIsSoftwareRenderingEnabled() {
+    return nativeGetIsSoftwareRenderingEnabled();
+  }
 
   @Nullable
   // TODO(mattcarroll): add javadocs
@@ -212,7 +216,12 @@ public boolean isAttached() {
   public void attachToNative(boolean isBackgroundView) {
     ensureRunningOnMainThread();
     ensureNotAttachedToNative();
-    nativePlatformViewId = nativeAttach(this, isBackgroundView);
+    nativePlatformViewId = performNativeAttach(this, isBackgroundView);
+  }
+
+  @VisibleForTesting
+  public long performNativeAttach(@NonNull FlutterJNI flutterJNI, boolean isBackgroundView) {
+    return nativeAttach(flutterJNI, isBackgroundView);
   }
 
   private native long nativeAttach(@NonNull FlutterJNI flutterJNI, boolean isBackgroundView);
@@ -279,7 +288,7 @@ public void removeIsDisplayingFlutterUiListener(@NonNull FlutterUiDisplayListene
   @SuppressWarnings("unused")
   @VisibleForTesting
   @UiThread
-  void onFirstFrame() {
+  public void onFirstFrame() {
     ensureRunningOnMainThread();
 
     for (FlutterUiDisplayListener listener : flutterUiDisplayListeners) {

shell/platform/android/io/flutter/embedding/engine/renderer/FlutterRenderer.java

@@ -314,7 +314,7 @@ private void unregisterTexture(long textureId) {
 
   // TODO(mattcarroll): describe the native behavior that this invokes
   public boolean isSoftwareRenderingEnabled() {
-    return flutterJNI.nativeGetIsSoftwareRenderingEnabled();
+    return flutterJNI.getIsSoftwareRenderingEnabled();
   }
 
   // TODO(mattcarroll): describe the native behavior that this invokes

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

@@ -713,7 +713,7 @@ public void onDisplayPlatformView(
       int width,
       int height,
       int viewWidth,
-      int ViewHeight,
+      int viewHeight,
       FlutterMutatorsStack mutatorsStack) {
     initializeRootImageViewIfNeeded();
     initializePlatformViewIfNeeded(viewId);
@@ -723,7 +723,7 @@ public void onDisplayPlatformView(
     mutatorView.setVisibility(View.VISIBLE);
     mutatorView.bringToFront();
 
-    FrameLayout.LayoutParams layoutParams = new FrameLayout.LayoutParams(viewWidth, ViewHeight);
+    FrameLayout.LayoutParams layoutParams = new FrameLayout.LayoutParams(viewWidth, viewHeight);
     View platformView = platformViews.get(viewId);
     platformView.setLayoutParams(layoutParams);
     platformView.bringToFront();
@@ -753,6 +753,20 @@ public void onBeginFrame() {
   }
 
   public void onEndFrame() {
+    final FlutterView view = (FlutterView) flutterView;
+    // If there are no platform views in the current frame,
+    // then revert the image view surface and use the previous surface.
+    //
+    // Otherwise, acquire the latest image.
+    if (flutterViewConvertedToImageView && currentFrameUsedPlatformViewIds.isEmpty()) {
+      flutterViewConvertedToImageView = false;
+      view.revertImageView(
+          () -> {
+            // Destroy overlay surfaces once the surface reversion is completed.
+            finishFrame(false);
+          });
+      return;
+    }
     // Whether the current frame was rendered using ImageReaders.
     //
     // Since the image readers may not have images available at this point,
@@ -762,22 +776,12 @@ public void onEndFrame() {
     // If one of the surfaces doesn't have an image, the frame may be incomplete and must be
     // dropped.
     // For example, a toolbar widget painted by Flutter may not be rendered.
-    boolean isFrameRenderedUsingImageReaders = false;
-
-    if (flutterViewConvertedToImageView) {
-      FlutterView view = (FlutterView) flutterView;
-      // If there are no platform views in the current frame,
-      // then revert the image view surface and use the previous surface.
-      //
-      // Otherwise, acquire the latest image.
-      if (currentFrameUsedPlatformViewIds.isEmpty()) {
-        view.revertImageView();
-        flutterViewConvertedToImageView = false;
-      } else {
-        isFrameRenderedUsingImageReaders = view.acquireLatestImageViewFrame();
-      }
-    }
+    boolean isFrameRenderedUsingImageReaders =
+        flutterViewConvertedToImageView && view.acquireLatestImageViewFrame();
+    finishFrame(isFrameRenderedUsingImageReaders);
+  }
 
+  private void finishFrame(boolean isFrameRenderedUsingImageReaders) {
     for (int i = 0; i < overlayLayerViews.size(); i++) {
       int overlayId = overlayLayerViews.keyAt(i);
       FlutterImageView overlayView = overlayLayerViews.valueAt(i);
@@ -818,6 +822,14 @@ public void onEndFrame() {
     }
   }
 
+  @VisibleForTesting
+  @TargetApi(19)
+  public FlutterOverlaySurface createOverlaySurface(@NonNull FlutterImageView imageView) {
+    final int id = nextOverlayLayerId++;
+    overlayLayerViews.put(id, imageView);
+    return new FlutterOverlaySurface(id, imageView.getSurface());
+  }
+
   @TargetApi(19)
   public FlutterOverlaySurface createOverlaySurface() {
     // Overlay surfaces have the same size as the background surface.
@@ -826,17 +838,12 @@ public FlutterOverlaySurface createOverlaySurface() {
     // if the drawings they contain have a different tight bound.
     //
     // The final view size is determined when its frame is set.
-    FlutterImageView imageView =
+    return createOverlaySurface(
         new FlutterImageView(
             flutterView.getContext(),
             flutterView.getWidth(),
             flutterView.getHeight(),
-            FlutterImageView.SurfaceKind.overlay);
-
-    int id = nextOverlayLayerId++;
-    overlayLayerViews.put(id, imageView);
-
-    return new FlutterOverlaySurface(id, imageView.getSurface());
+            FlutterImageView.SurfaceKind.overlay));
   }
 
   public void destroyOverlaySurfaces() {

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

@@ -169,7 +169,7 @@ public FlutterView(Context context, AttributeSet attrs, FlutterNativeView native
 
     dartExecutor = mNativeView.getDartExecutor();
     flutterRenderer = new FlutterRenderer(mNativeView.getFlutterJNI());
-    mIsSoftwareRenderingEnabled = mNativeView.getFlutterJNI().nativeGetIsSoftwareRenderingEnabled();
+    mIsSoftwareRenderingEnabled = mNativeView.getFlutterJNI().getIsSoftwareRenderingEnabled();
     mMetrics = new ViewportMetrics();
     mMetrics.devicePixelRatio = context.getResources().getDisplayMetrics().density;
     setFocusable(true);