[camerax] Add flash configuration for image capture (#3800)

Implements off, auto, and always flash configurations for image capture.

Part of https://github.com/flutter/flutter/issues/120715.

packages/camera/camera_android_camerax/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.5.0+10
+
+* Implements off, auto, and always flash mode configurations for image capture.
+
 ## 0.5.0+9
 
 * Marks all Dart-wrapped Android native classes as `@immutable`.

packages/camera/camera_android_camerax/README.md

@@ -35,7 +35,7 @@ Any specified `ResolutionPreset` wll go unused in favor of CameraX defaults and
 
 ### Flash mode configuration \[[Issue #120715][120715]\]
 
-`setFlashMode` is unimplemented.
+Calling `setFlashMode` with mode `FlashMode.torch` currently does nothing.
 
 ### Exposure mode, point, & offset configuration \[[Issue #120468][120468]\]
 

packages/camera/camera_android_camerax/lib/src/android_camera_camerax.dart

@@ -104,6 +104,9 @@ class AndroidCameraCameraX extends CameraPlatform {
   @visibleForTesting
   ImageCapture? imageCapture;
 
+  /// The flash mode currently configured for [imageCapture].
+  int? _currentFlashMode;
+
   /// The [ImageAnalysis] instance that can be configured to analyze individual
   /// frames.
   ImageAnalysis? imageAnalysis;
@@ -459,13 +462,32 @@ class AndroidCameraCameraX extends CameraPlatform {
   /// [cameraId] is not used.
   @override
   Future<XFile> takePicture(int cameraId) async {
-    // TODO(camsim99): Add support for flash mode configuration.
-    // https://github.com/flutter/flutter/issues/120715
+    if (_currentFlashMode != null) {
+      await imageCapture!.setFlashMode(_currentFlashMode!);
+    }
     final String picturePath = await imageCapture!.takePicture();
-
     return XFile(picturePath);
   }
 
+  /// Sets the flash mode for the selected camera.
+  @override
+  Future<void> setFlashMode(int cameraId, FlashMode mode) async {
+    switch (mode) {
+      case FlashMode.off:
+        _currentFlashMode = ImageCapture.flashModeOff;
+        break;
+      case FlashMode.auto:
+        _currentFlashMode = ImageCapture.flashModeAuto;
+        break;
+      case FlashMode.always:
+        _currentFlashMode = ImageCapture.flashModeOn;
+        break;
+      case FlashMode.torch:
+        // TODO(camsim99): Implement torch mode when CameraControl is wrapped.
+        break;
+    }
+  }
+
   /// Configures and starts a video recording. Returns silently without doing
   /// anything if there is currently an active recording.
   @override

packages/camera/camera_android_camerax/pubspec.yaml

@@ -2,7 +2,7 @@ name: camera_android_camerax
 description: Android implementation of the camera plugin using the CameraX library.
 repository: https://github.com/flutter/packages/tree/main/packages/camera/camera_android_camerax
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+camera%22
-version: 0.5.0+9
+version: 0.5.0+10
 
 environment:
   sdk: ">=2.19.0 <4.0.0"

packages/camera/camera_android_camerax/test/android_camera_camerax_test.dart

@@ -779,8 +779,6 @@ void main() {
     final AndroidCameraCameraX camera = AndroidCameraCameraX();
     const String testPicturePath = 'test/absolute/path/to/picture';
 
-    camera.processCameraProvider = MockProcessCameraProvider();
-    camera.cameraSelector = MockCameraSelector();
     camera.imageCapture = MockImageCapture();
 
     when(camera.imageCapture!.takePicture())
@@ -791,6 +789,41 @@ void main() {
     expect(imageFile.path, equals(testPicturePath));
   });
 
+  test('setFlashMode configures ImageCapture with expected flash mode',
+      () async {
+    final AndroidCameraCameraX camera = AndroidCameraCameraX();
+    const int cameraId = 22;
+
+    camera.imageCapture = MockImageCapture();
+
+    for (final FlashMode flashMode in FlashMode.values) {
+      await camera.setFlashMode(cameraId, flashMode);
+
+      int? expectedFlashMode;
+      switch (flashMode) {
+        case FlashMode.off:
+          expectedFlashMode = ImageCapture.flashModeOff;
+          break;
+        case FlashMode.auto:
+          expectedFlashMode = ImageCapture.flashModeAuto;
+          break;
+        case FlashMode.always:
+          expectedFlashMode = ImageCapture.flashModeOn;
+          break;
+        case FlashMode.torch:
+          // TODO(camsim99): Test torch mode when implemented.
+          break;
+      }
+
+      if (expectedFlashMode == null) {
+        continue;
+      }
+
+      await camera.takePicture(cameraId);
+      verify(camera.imageCapture!.setFlashMode(expectedFlashMode));
+    }
+  });
+
   test('getMinExposureOffset returns expected exposure offset', () async {
     final AndroidCameraCameraX camera = AndroidCameraCameraX();
     final MockCameraInfo mockCameraInfo = MockCameraInfo();