Ensure that unregisterTexture is called when forget to call SurfaceTextureEntry.release (flutter/engine#28304)

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

@@ -39,6 +39,7 @@ public class FlutterRenderer implements TextureRegistry {
   @NonNull private final AtomicLong nextTextureId = new AtomicLong(0L);
   @Nullable private Surface surface;
   private boolean isDisplayingFlutterUi = false;
+  private Handler handler = new Handler();
 
   @NonNull
   private final FlutterUiDisplayListener flutterUiDisplayListener =
@@ -168,6 +169,38 @@ public class FlutterRenderer implements TextureRegistry {
       unregisterTexture(id);
       released = true;
     }
+
+    @Override
+    protected void finalize() throws Throwable {
+      try {
+        if (released) {
+          return;
+        }
+
+        handler.post(new SurfaceTextureFinalizerRunnable(id, flutterJNI));
+      } finally {
+        super.finalize();
+      }
+    }
+  }
+
+  static final class SurfaceTextureFinalizerRunnable implements Runnable {
+    private final long id;
+    private final FlutterJNI flutterJNI;
+
+    SurfaceTextureFinalizerRunnable(long id, @NonNull FlutterJNI flutterJNI) {
+      this.id = id;
+      this.flutterJNI = flutterJNI;
+    }
+
+    @Override
+    public void run() {
+      if (!flutterJNI.isAttached()) {
+        return;
+      }
+      Log.v(TAG, "Releasing a SurfaceTexture (" + id + ").");
+      flutterJNI.unregisterTexture(id);
+    }
   }
   // ------ END TextureRegistry IMPLEMENTATION ----
 

engine/src/flutter/shell/platform/android/test/io/flutter/embedding/engine/renderer/FlutterRendererTest.java

@@ -4,9 +4,14 @@ import static org.mockito.Matchers.eq;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+import static org.robolectric.Shadows.shadowOf;
 
+import android.os.Looper;
 import android.view.Surface;
 import io.flutter.embedding.engine.FlutterJNI;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -116,4 +121,78 @@ public class FlutterRendererTest {
     // Verify behavior under test.
     verify(fakeFlutterJNI, times(0)).markTextureFrameAvailable(eq(entry.id()));
   }
+
+  @Test
+  public void itUnregistersTextureWhenSurfaceTextureFinalized() {
+    // Setup the test.
+    FlutterJNI fakeFlutterJNI = mock(FlutterJNI.class);
+    when(fakeFlutterJNI.isAttached()).thenReturn(true);
+    FlutterRenderer flutterRenderer = new FlutterRenderer(fakeFlutterJNI);
+
+    fakeFlutterJNI.detachFromNativeAndReleaseResources();
+
+    FlutterRenderer.SurfaceTextureRegistryEntry entry =
+        (FlutterRenderer.SurfaceTextureRegistryEntry) flutterRenderer.createSurfaceTexture();
+    long id = entry.id();
+
+    flutterRenderer.startRenderingToSurface(fakeSurface);
+
+    // Execute the behavior under test.
+    runFinalization(entry);
+
+    shadowOf(Looper.getMainLooper()).idle();
+
+    flutterRenderer.stopRenderingToSurface();
+
+    // Verify behavior under test.
+    verify(fakeFlutterJNI, times(1)).unregisterTexture(eq(id));
+  }
+
+  @Test
+  public void itStopsUnregisteringTextureWhenDetached() {
+    // Setup the test.
+    FlutterJNI fakeFlutterJNI = mock(FlutterJNI.class);
+    when(fakeFlutterJNI.isAttached()).thenReturn(false);
+    FlutterRenderer flutterRenderer = new FlutterRenderer(fakeFlutterJNI);
+
+    fakeFlutterJNI.detachFromNativeAndReleaseResources();
+
+    FlutterRenderer.SurfaceTextureRegistryEntry entry =
+        (FlutterRenderer.SurfaceTextureRegistryEntry) flutterRenderer.createSurfaceTexture();
+    long id = entry.id();
+
+    flutterRenderer.startRenderingToSurface(fakeSurface);
+
+    flutterRenderer.stopRenderingToSurface();
+
+    // Execute the behavior under test.
+    runFinalization(entry);
+
+    shadowOf(Looper.getMainLooper()).idle();
+
+    // Verify behavior under test.
+    verify(fakeFlutterJNI, times(0)).unregisterTexture(eq(id));
+  }
+
+  void runFinalization(FlutterRenderer.SurfaceTextureRegistryEntry entry) {
+    CountDownLatch latch = new CountDownLatch(1);
+    Thread fakeFinalizer =
+        new Thread(
+            new Runnable() {
+              public void run() {
+                try {
+                  entry.finalize();
+                  latch.countDown();
+                } catch (Throwable e) {
+                  // do nothing
+                }
+              }
+            });
+    fakeFinalizer.start();
+    try {
+      latch.await(5L, TimeUnit.SECONDS);
+    } catch (Throwable e) {
+      // do nothing
+    }
+  }
 }