[camera] Expanded platform interface to support setting flash mode (#3313)

* Expanded platform interface so support setting flash mode

* Formatted dart code

* Manually serialize flash mode enum rather than relying on stringification.

* Add default to flash mode serialization

Author: BeMacized

packages/camera/camera_platform_interface/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 1.0.1
+
+- Added interface methods for setting flash mode.
+
 ## 1.0.0
 
 - Initial open-source release

packages/camera/camera_platform_interface/lib/src/method_channel/method_channel_camera.dart

@@ -175,11 +175,35 @@ class MethodChannelCamera extends CameraPlatform {
         <String, dynamic>{'cameraId': cameraId},
       );
 
+  @override
+  Future<void> setFlashMode(int cameraId, FlashMode mode) =>
+      _channel.invokeMethod<void>(
+        'setFlashMode',
+        <String, dynamic>{
+          'cameraId': cameraId,
+          'mode': _serializeFlashMode(mode),
+        },
+      );
+
   @override
   Widget buildPreview(int cameraId) {
     return Texture(textureId: cameraId);
   }
 
+  /// Returns the flash mode as a String.
+  String _serializeFlashMode(FlashMode flashMode) {
+    switch (flashMode) {
+      case FlashMode.off:
+        return 'off';
+      case FlashMode.auto:
+        return 'auto';
+      case FlashMode.always:
+        return 'always';
+      default:
+        throw ArgumentError('Unknown FlashMode value');
+    }
+  }
+
   /// Returns the resolution preset as a String.
   String _serializeResolutionPreset(ResolutionPreset resolutionPreset) {
     switch (resolutionPreset) {

packages/camera/camera_platform_interface/lib/src/platform_interface/camera_platform.dart

@@ -108,6 +108,11 @@ abstract class CameraPlatform extends PlatformInterface {
     throw UnimplementedError('resumeVideoRecording() is not implemented.');
   }
 
+  /// Sets the flash mode for taking pictures.
+  Future<void> setFlashMode(int cameraId, FlashMode mode) {
+    throw UnimplementedError('setFlashMode() is not implemented.');
+  }
+
   /// Returns a widget showing a live camera preview.
   Widget buildPreview(int cameraId) {
     throw UnimplementedError('buildView() has not been implemented.');

packages/camera/camera_platform_interface/lib/src/types/flash_mode.dart

@@ -0,0 +1,15 @@
+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+/// The possible flash modes that can be set for a camera
+enum FlashMode {
+  /// Do not use the flash when taking a picture.
+  off,
+
+  /// Let the device decide whether to flash the camera when taking a picture.
+  auto,
+
+  /// Always use the flash when taking a picture.
+  always,
+}

packages/camera/camera_platform_interface/lib/src/types/types.dart

@@ -5,3 +5,4 @@
 export 'camera_description.dart';
 export 'resolution_preset.dart';
 export 'camera_exception.dart';
+export 'flash_mode.dart';

packages/camera/camera_platform_interface/pubspec.yaml

@@ -3,7 +3,7 @@ description: A common platform interface for the camera plugin.
 homepage: https://github.com/flutter/plugins/tree/master/packages/camera/camera_platform_interface
 # NOTE: We strongly prefer non-breaking changes, even at the expense of a
 # less-clean API. See https://flutter.dev/go/platform-interface-breaking-changes
-version: 1.0.0
+version: 1.0.1
 
 dependencies:
   flutter:

packages/camera/camera_platform_interface/test/camera_platform_interface_test.dart

@@ -173,6 +173,19 @@ void main() {
       );
     });
 
+    test(
+        'Default implementation of setFlashMode() should throw unimplemented error',
+        () {
+      // Arrange
+      final cameraPlatform = ExtendsCameraPlatform();
+
+      // Act & Assert
+      expect(
+        () => cameraPlatform.setFlashMode(1, null),
+        throwsUnimplementedError,
+      );
+    });
+
     test(
         'Default implementation of startVideoRecording() should throw unimplemented error',
         () {

packages/camera/camera_platform_interface/test/method_channel/method_channel_camera_test.dart

@@ -470,6 +470,29 @@ void main() {
         ]);
       });
 
+      test('Should set the flash mode', () async {
+        // Arrange
+        MethodChannelMock channel = MethodChannelMock(
+          channelName: 'plugins.flutter.io/camera',
+          methods: {'setFlashMode': null},
+        );
+
+        // Act
+        await camera.setFlashMode(cameraId, FlashMode.always);
+        await camera.setFlashMode(cameraId, FlashMode.auto);
+        await camera.setFlashMode(cameraId, FlashMode.off);
+
+        // Assert
+        expect(channel.log, <Matcher>[
+          isMethodCall('setFlashMode',
+              arguments: {'cameraId': cameraId, 'mode': 'always'}),
+          isMethodCall('setFlashMode',
+              arguments: {'cameraId': cameraId, 'mode': 'auto'}),
+          isMethodCall('setFlashMode',
+              arguments: {'cameraId': cameraId, 'mode': 'off'}),
+        ]);
+      });
+
       test('Should build a texture widget as preview widget', () async {
         // Act
         Widget widget = camera.buildPreview(cameraId);

packages/camera/camera_platform_interface/test/types/flash_mode_test.dart

@@ -0,0 +1,22 @@
+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:camera_platform_interface/camera_platform_interface.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  test('FlashMode should contain 3 options', () {
+    final values = FlashMode.values;
+
+    expect(values.length, 3);
+  });
+
+  test("FlashMode enum should have items in correct index", () {
+    final values = FlashMode.values;
+
+    expect(values[0], FlashMode.off);
+    expect(values[1], FlashMode.auto);
+    expect(values[2], FlashMode.always);
+  });
+}