From 438c737e982f19ecffe3850119bceb41503252bb Mon Sep 17 00:00:00 2001
From: Nayuta403 <40540394+Nayuta403@users.noreply.github.com>
Date: Mon, 4 Jul 2022 10:39:03 +0800
Subject: [PATCH] Avoid crash caused by flutterImageView be null
 (flutter/engine#34395)

---
 .../embedding/android/FlutterView.java        |  7 ++++-
 .../embedding/android/FlutterViewTest.java    | 26 +++++++++++++++++++
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/engine/src/flutter/shell/platform/android/io/flutter/embedding/android/FlutterView.java b/engine/src/flutter/shell/platform/android/io/flutter/embedding/android/FlutterView.java
index f63e899b4e8..53cc25e1773 100644
--- a/engine/src/flutter/shell/platform/android/io/flutter/embedding/android/FlutterView.java
+++ b/engine/src/flutter/shell/platform/android/io/flutter/embedding/android/FlutterView.java
@@ -1308,6 +1308,11 @@ public class FlutterView extends FrameLayout
         getContext(), getWidth(), getHeight(), FlutterImageView.SurfaceKind.background);
   }
 
+  @VisibleForTesting
+  public FlutterImageView getCurrentImageSurface() {
+    return flutterImageView;
+  }
+
   /**
    * 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.
@@ -1370,7 +1375,7 @@ public class FlutterView extends FrameLayout
           public void onFlutterUiDisplayed() {
             renderer.removeIsDisplayingFlutterUiListener(this);
             onDone.run();
-            if (!(renderSurface instanceof FlutterImageView)) {
+            if (!(renderSurface instanceof FlutterImageView) && flutterImageView != null) {
               flutterImageView.detachFromRenderer();
             }
           }
diff --git a/engine/src/flutter/shell/platform/android/test/io/flutter/embedding/android/FlutterViewTest.java b/engine/src/flutter/shell/platform/android/test/io/flutter/embedding/android/FlutterViewTest.java
index 91b9244e4d8..beb05cc29e8 100644
--- a/engine/src/flutter/shell/platform/android/test/io/flutter/embedding/android/FlutterViewTest.java
+++ b/engine/src/flutter/shell/platform/android/test/io/flutter/embedding/android/FlutterViewTest.java
@@ -174,6 +174,32 @@ public class FlutterViewTest {
     verify(imageViewMock, times(1)).closeImageReader();
   }
 
+  @Test
+  public void flutterImageView_revertImageViewAndAvoidNPE() {
+    FlutterView flutterView = new FlutterView(ctx);
+    FlutterEngine flutterEngine = spy(new FlutterEngine(ctx, mockFlutterLoader, mockFlutterJni));
+    FlutterRenderer flutterRenderer = spy(new FlutterRenderer(mockFlutterJni));
+    when(flutterEngine.getRenderer()).thenReturn(flutterRenderer);
+
+    flutterView.attachToFlutterEngine(flutterEngine);
+    flutterView.convertToImageView();
+    assertTrue(flutterView.renderSurface instanceof FlutterImageView);
+
+    // Register a `FlutterUiDisplayListener` callback.
+    // During callback execution it will invoke `flutterImageView.detachFromRenderer()`.
+    flutterView.revertImageView(
+        () -> {
+          // No-op
+        });
+    assertFalse(flutterView.renderSurface instanceof FlutterImageView);
+
+    flutterView.detachFromFlutterEngine();
+    assertEquals(null, flutterView.getCurrentImageSurface());
+
+    // Invoke all registered `FlutterUiDisplayListener` callback
+    mockFlutterJni.onFirstFrame();
+  }
+
   @Test
   public void onConfigurationChanged_fizzlesWhenNullEngine() {
     FlutterView flutterView = new FlutterView(Robolectric.setupActivity(Activity.class));