Support passing existing SurfaceTexture to TextureRegistry (#28358)

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

@@ -90,12 +90,22 @@ public class FlutterRenderer implements TextureRegistry {
 
   // ------ START TextureRegistry IMPLEMENTATION -----
   /**
-   * Creates and returns a new {@link SurfaceTexture} that is also made available to Flutter code.
+   * Creates and returns a new {@link SurfaceTexture} managed by the Flutter engine that is also
+   * made available to Flutter code.
    */
   @Override
   public SurfaceTextureEntry createSurfaceTexture() {
     Log.v(TAG, "Creating a SurfaceTexture.");
     final SurfaceTexture surfaceTexture = new SurfaceTexture(0);
+    return registerSurfaceTexture(surfaceTexture);
+  }
+
+  /**
+   * Registers and returns a {@link SurfaceTexture} managed by the Flutter engine that is also made
+   * available to Flutter code.
+   */
+  @Override
+  public SurfaceTextureEntry registerSurfaceTexture(@NonNull SurfaceTexture surfaceTexture) {
     surfaceTexture.detachFromGLContext();
     final SurfaceTextureRegistryEntry entry =
         new SurfaceTextureRegistryEntry(nextTextureId.getAndIncrement(), surfaceTexture);

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

@@ -873,6 +873,12 @@ public class FlutterView extends SurfaceView
   @Override
   public TextureRegistry.SurfaceTextureEntry createSurfaceTexture() {
     final SurfaceTexture surfaceTexture = new SurfaceTexture(0);
+    return registerSurfaceTexture(surfaceTexture);
+  }
+
+  @Override
+  public TextureRegistry.SurfaceTextureEntry registerSurfaceTexture(
+      @NonNull SurfaceTexture surfaceTexture) {
     surfaceTexture.detachFromGLContext();
     final SurfaceTextureRegistryEntry entry =
         new SurfaceTextureRegistryEntry(nextTextureId.getAndIncrement(), surfaceTexture);

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

@@ -5,6 +5,7 @@
 package io.flutter.view;
 
 import android.graphics.SurfaceTexture;
+import androidx.annotation.NonNull;
 
 // TODO(mattcarroll): re-evalute docs in this class and add nullability annotations.
 /**
@@ -20,6 +21,13 @@ public interface TextureRegistry {
    */
   SurfaceTextureEntry createSurfaceTexture();
 
+  /**
+   * Registers a SurfaceTexture managed by the Flutter engine.
+   *
+   * @return A SurfaceTextureEntry.
+   */
+  SurfaceTextureEntry registerSurfaceTexture(@NonNull SurfaceTexture surfaceTexture);
+
   /** A registry entry for a managed SurfaceTexture. */
   interface SurfaceTextureEntry {
     /** @return The managed SurfaceTexture. */

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

 package io.flutter.embedding.engine.renderer;
 
+import static org.junit.Assert.assertEquals;
 import static org.mockito.Matchers.eq;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.times;
@@ -7,6 +8,7 @@ import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 import static org.robolectric.Shadows.shadowOf;
 
+import android.graphics.SurfaceTexture;
 import android.os.Looper;
 import android.view.Surface;
 import io.flutter.embedding.engine.FlutterJNI;
@@ -122,6 +124,28 @@ public class FlutterRendererTest {
     verify(fakeFlutterJNI, times(0)).markTextureFrameAvailable(eq(entry.id()));
   }
 
+  @Test
+  public void itRegistersExistingSurfaceTexture() {
+    // Setup the test.
+    FlutterRenderer flutterRenderer = new FlutterRenderer(fakeFlutterJNI);
+
+    fakeFlutterJNI.detachFromNativeAndReleaseResources();
+
+    SurfaceTexture surfaceTexture = new SurfaceTexture(0);
+
+    // Execute the behavior under test.
+    FlutterRenderer.SurfaceTextureRegistryEntry entry =
+        (FlutterRenderer.SurfaceTextureRegistryEntry)
+            flutterRenderer.registerSurfaceTexture(surfaceTexture);
+
+    flutterRenderer.startRenderingToSurface(fakeSurface);
+
+    // Verify behavior under test.
+    assertEquals(surfaceTexture, entry.surfaceTexture());
+
+    verify(fakeFlutterJNI, times(1)).registerTexture(eq(entry.id()), eq(entry.textureWrapper()));
+  }
+
   @Test
   public void itUnregistersTextureWhenSurfaceTextureFinalized() {
     // Setup the test.

shell/platform/android/test/io/flutter/plugin/platform/PlatformViewsControllerTest.java

@@ -849,6 +849,11 @@ public class PlatformViewsControllerTest {
 
           @Override
           public SurfaceTextureEntry createSurfaceTexture() {
+            return registerSurfaceTexture(mock(SurfaceTexture.class));
+          }
+
+          @Override
+          public SurfaceTextureEntry registerSurfaceTexture(SurfaceTexture surfaceTexture) {
             return new SurfaceTextureEntry() {
               @Override
               public SurfaceTexture surfaceTexture() {