[camera_android] Wait for creating capture session when initializing (flutter#8894)

As discussed in the linked issue, this is an attempt to palliate one of the thread race conditions. In particular, returning to Dart possibly before creating the session and then let other function like "startImageStream" create a different session in parallel and interleave, causing the `java.lang.IllegalArgumentException: CaptureRequest contains unconfigured Input/Output Surface!` error.

Fixes flutter/flutter#165092

cc @camsim99 

## Pre-Review Checklist

[^1]: Regular contributors who have demonstrated familiarity with the repository guidelines only need to comment if the PR is not auto-exempted by repo tooling.

Author: davidmartos96

packages/camera/camera_android/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.10.10+3
+
+* Waits for the creation of the capture session when initializing the camera to avoid thread race conditions.
+
 ## 0.10.10+2
 
 * Don't set the FPS range unless video recording. It can cause dark image previews on some devices becuse the auto exposure algorithm is more constrained after fixing the min/max FPS range to the same value. This change has the side effect that providing the `fps` parameter will not affect the camera preview when not video recording. And if you need a lower frame rate in your image streaming handler, you can skip frames by checking the time it passed since the last frame.

packages/camera/camera_android/android/src/main/java/io/flutter/plugins/camera/Camera.java

@@ -372,16 +372,19 @@ public void open(Integer imageFormatGroup) throws CameraAccessException {
           public void onOpened(@NonNull CameraDevice device) {
             cameraDevice = new DefaultCameraDeviceWrapper(device);
             try {
-              startPreview();
-              if (!recordingVideo) { // only send initialization if we werent already recording and switching cameras
-                dartMessenger.sendCameraInitializedEvent(
-                    resolutionFeature.getPreviewSize().getWidth(),
-                    resolutionFeature.getPreviewSize().getHeight(),
-                    cameraFeatures.getExposureLock().getValue(),
-                    cameraFeatures.getAutoFocus().getValue(),
-                    cameraFeatures.getExposurePoint().checkIsSupported(),
-                    cameraFeatures.getFocusPoint().checkIsSupported());
-              }
+              // only send initialization if we werent already recording and switching cameras
+              Runnable onSuccess =
+                  recordingVideo
+                      ? null
+                      : () ->
+                          dartMessenger.sendCameraInitializedEvent(
+                              resolutionFeature.getPreviewSize().getWidth(),
+                              resolutionFeature.getPreviewSize().getHeight(),
+                              cameraFeatures.getExposureLock().getValue(),
+                              cameraFeatures.getAutoFocus().getValue(),
+                              cameraFeatures.getExposurePoint().checkIsSupported(),
+                              cameraFeatures.getFocusPoint().checkIsSupported());
+              startPreview(onSuccess);
             } catch (Exception e) {
               String message =
                   (e.getMessage() == null)
@@ -870,7 +873,8 @@ public String stopVideoRecording() {
     }
     mediaRecorder.reset();
     try {
-      startPreview();
+      // Don't wait for start preview
+      startPreview(null);
     } catch (CameraAccessException | IllegalStateException | InterruptedException e) {
       throw new Messages.FlutterError("videoRecordingFailed", e.getMessage(), null);
     }
@@ -1159,24 +1163,40 @@ public void resumePreview() {
         null, (code, message) -> dartMessenger.sendCameraErrorEvent(message));
   }
 
-  public void startPreview() throws CameraAccessException, InterruptedException {
+  public void startPreview(@Nullable Runnable onSuccessCallback)
+      throws CameraAccessException, InterruptedException {
     // If recording is already in progress, the camera is being flipped, so send it through the VideoRenderer to keep the correct orientation.
     if (recordingVideo) {
-      startPreviewWithVideoRendererStream();
+      startPreviewWithVideoRendererStream(onSuccessCallback);
     } else {
-      startRegularPreview();
+      startRegularPreview(onSuccessCallback);
     }
   }
 
-  private void startRegularPreview() throws CameraAccessException {
-    if (pictureImageReader == null || pictureImageReader.getSurface() == null) return;
+  private void startRegularPreview(@Nullable Runnable onSuccessCallback)
+      throws CameraAccessException {
+    if (pictureImageReader == null || pictureImageReader.getSurface() == null) {
+      // noop
+      if (onSuccessCallback != null) {
+        onSuccessCallback.run();
+      }
+      return;
+    }
+
     Log.i(TAG, "startPreview");
-    createCaptureSession(CameraDevice.TEMPLATE_PREVIEW, pictureImageReader.getSurface());
+    createCaptureSession(
+        CameraDevice.TEMPLATE_PREVIEW, onSuccessCallback, pictureImageReader.getSurface());
   }
 
-  private void startPreviewWithVideoRendererStream()
+  private void startPreviewWithVideoRendererStream(@Nullable Runnable onSuccessCallback)
       throws CameraAccessException, InterruptedException {
-    if (videoRenderer == null) return;
+    if (videoRenderer == null) {
+      // noop
+      if (onSuccessCallback != null) {
+        onSuccessCallback.run();
+      }
+      return;
+    }
 
     // get rotation for rendered video
     final PlatformChannel.DeviceOrientation lockedOrientation =
@@ -1200,7 +1220,8 @@ private void startPreviewWithVideoRendererStream()
     }
     videoRenderer.setRotation(rotation);
 
-    createCaptureSession(CameraDevice.TEMPLATE_RECORD, videoRenderer.getInputSurface());
+    createCaptureSession(
+        CameraDevice.TEMPLATE_RECORD, onSuccessCallback, videoRenderer.getInputSurface());
   }
 
   public void startPreviewWithImageStream(EventChannel imageStreamChannel)

packages/camera/camera_android/android/src/main/java/io/flutter/plugins/camera/CameraApiImpl.java

@@ -282,7 +282,8 @@ public void startImageStream() {
   @Override
   public void stopImageStream() {
     try {
-      camera.startPreview();
+      // Don't wait for start preview
+      camera.startPreview(null);
     } catch (Exception e) {
       throw new Messages.FlutterError(e.getClass().getName(), e.getMessage(), null);
     }

packages/camera/camera_android/android/src/test/java/io/flutter/plugins/camera/CameraTest.java

@@ -14,6 +14,7 @@
 
 import android.app.Activity;
 import android.content.Context;
+import android.graphics.ImageFormat;
 import android.graphics.SurfaceTexture;
 import android.hardware.camera2.*;
 import android.hardware.camera2.params.SessionConfiguration;
@@ -64,9 +65,11 @@
 import org.junit.Before;
 import org.junit.Test;
 import org.mockito.ArgumentMatcher;
+import org.mockito.InOrder;
 import org.mockito.MockedConstruction;
 import org.mockito.MockedStatic;
 import org.mockito.Mockito;
+import org.mockito.stubbing.Answer;
 
 /**
  * As Pigeon-generated class, including FlutterError, do not implement equality, this helper class
@@ -134,6 +137,7 @@ public void close() {}
 }
 
 public class CameraTest {
+  private Activity mockActivity;
   private CameraProperties mockCameraProperties;
   private TestCameraFeatureFactory mockCameraFeatureFactory;
   private DartMessenger mockDartMessenger;
@@ -160,9 +164,10 @@ public void before() {
     mockHandlerFactory = mockStatic(Camera.HandlerFactory.class);
     mockHandler = mock(Handler.class);
 
-    final Activity mockActivity = mock(Activity.class);
-    final TextureRegistry.SurfaceTextureEntry mockFlutterTexture =
+    mockActivity = mock(Activity.class);
+    TextureRegistry.SurfaceTextureEntry mockFlutterTexture =
         mock(TextureRegistry.SurfaceTextureEntry.class);
+    when(mockFlutterTexture.surfaceTexture()).thenReturn(mock(SurfaceTexture.class));
     final String cameraName = "1";
     final ResolutionPreset resolutionPreset = ResolutionPreset.high;
     final boolean enableAudio = false;
@@ -211,6 +216,67 @@ public void after() throws IOException {
     mockRangeConstruction.close();
   }
 
+  @Test
+  public void shouldSendCameraInitEventAfterCreatingTheSession()
+      throws CameraAccessException, InterruptedException {
+    // A spy is used so that we can properly configure the camera class with appropriate mocks
+    // when camera.startPreview is called
+    camera = spy(camera);
+
+    // Setup ImageReader
+    final ImageReader mockImageReader = mock(ImageReader.class);
+    final Surface mockSurface = mock(Surface.class);
+    when(mockImageReader.getSurface()).thenReturn(mockSurface);
+
+    // Setup camera device.
+    ArrayList<CaptureRequest.Builder> mockRequestBuilders = new ArrayList<>();
+    mockRequestBuilders.add(mock(CaptureRequest.Builder.class));
+    CameraDeviceWrapper fakeCameraDevice =
+        new FakeCameraDeviceWrapper(mockRequestBuilders, mock(CameraCaptureSession.class));
+
+    // When starting the preview, initialize with mock properties
+    doAnswer(
+            invocation -> {
+              camera.cameraDevice = fakeCameraDevice;
+              camera.pictureImageReader = mockImageReader;
+              return invocation.callRealMethod();
+            })
+        .when(camera)
+        .startPreview(any());
+
+    // Setup CameraManager
+    final CameraManager mockCameraManager = mock(CameraManager.class);
+    when(mockActivity.getSystemService(Context.CAMERA_SERVICE)).thenReturn(mockCameraManager);
+
+    // Trigger the onOpened callback when calling CameraManager.openCamera.
+    doAnswer(
+            (Answer<Object>)
+                invocation -> {
+                  CameraDevice.StateCallback cb = invocation.getArgument(1);
+                  cb.onOpened(mock(CameraDevice.class));
+                  return null;
+                })
+        .when(mockCameraManager)
+        .openCamera(any(), any(), any(Handler.class));
+
+    // Setup ResolutionFeature
+    ResolutionFeature resolutionFeature = mockCameraFeatureFactory.mockResolutionFeature;
+    when(resolutionFeature.checkIsSupported()).thenReturn(true);
+    final Size mockSize = mock(Size.class);
+    when(resolutionFeature.getPreviewSize()).thenReturn(mockSize);
+    when(resolutionFeature.getCaptureSize()).thenReturn(mockSize);
+
+    // Actual test that opens the camera, that mimics the camera initialize call.
+    camera.open(ImageFormat.JPEG);
+
+    // Make sure that the initialize event is called after configuring the session
+    InOrder inOrder = inOrder(camera.captureSession, mockDartMessenger);
+    inOrder.verify(camera.captureSession, times(1)).setRepeatingRequest(any(), any(), any());
+    inOrder
+        .verify(mockDartMessenger, times(1))
+        .sendCameraInitializedEvent(any(), any(), any(), any(), any(), any());
+  }
+
   @Test
   public void shouldNotImplementLifecycleObserverInterface() {
     Class<Camera> cameraClass = Camera.class;
@@ -705,7 +771,7 @@ public void startPreview_shouldPullStreamFromVideoRenderer()
     when(cameraFlutterTexture.surfaceTexture()).thenReturn(mockSurfaceTexture);
     when(resolutionFeature.getPreviewSize()).thenReturn(mockSize);
 
-    camera.startPreview();
+    camera.startPreview(null);
     verify(mockVideoRenderer, times(1))
         .getInputSurface(); // stream pulled from videoRenderer's surface.
   }
@@ -730,7 +796,7 @@ public void startPreview_shouldPullStreamFromImageReader()
     when(resolutionFeature.getPreviewSize()).thenReturn(mockSize);
     when(mockImageReader.getSurface()).thenReturn(mock(Surface.class));
 
-    camera.startPreview();
+    camera.startPreview(null);
     verify(mockImageReader, times(2)) // we expect two calls to start regular preview.
         .getSurface(); // stream pulled from regular imageReader's surface.
   }
@@ -757,7 +823,7 @@ public void startPreview_shouldFlipRotation() throws InterruptedException, Camer
     when(resolutionFeature.getPreviewSize()).thenReturn(mockSize);
     when(mockCameraProperties.getLensFacing()).thenReturn(CameraMetadata.LENS_FACING_FRONT);
 
-    camera.startPreview();
+    camera.startPreview(null);
     verify(mockVideoRenderer, times(1)).setRotation(180);
   }
 

packages/camera/camera_android/pubspec.yaml

@@ -3,7 +3,7 @@ description: Android implementation of the camera plugin.
 repository: https://github.com/flutter/packages/tree/main/packages/camera/camera_android
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+camera%22
 
-version: 0.10.10+2
+version: 0.10.10+3
 
 environment:
   sdk: ^3.6.0