[camera][draft] Add camera plugin (#29)

Added the first draft version, but there are still a lot of unimplemented features.

packages/camera/elinux/method_channel/method_channel_camera.h

@@ -0,0 +1,37 @@
+// Copyright 2021 Sony Group Corporation. All rights reserved.
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef PACKAGES_CAMERA_CAMERA_ELINUX_CAMERA_METHOD_CHANNEL_METHOD_CHANNEL_CAMERA_H_
+#define PACKAGES_CAMERA_CAMERA_ELINUX_CAMERA_METHOD_CHANNEL_METHOD_CHANNEL_CAMERA_H_
+
+#include <flutter/encodable_value.h>
+#include <flutter/method_channel.h>
+#include <flutter/plugin_registrar.h>
+
+#include <string>
+
+#include "events/camera_initialized_event.h"
+
+enum class CameraEventType {
+  kError,
+  kCameraClosing,
+  kInitialized,
+};
+
+class MethodChannelCamera {
+ public:
+  MethodChannelCamera(flutter::PluginRegistrar* registrar, int64_t camera_id);
+  ~MethodChannelCamera() = default;
+
+  void SendInitializedEvent(CameraInitializedEvent& message);
+
+ private:
+  void Send(const std::string& method,
+            std::unique_ptr<flutter::EncodableValue>&& arguments);
+
+  std::unique_ptr<flutter::MethodChannel<flutter::EncodableValue>> channel_;
+};
+
+#endif  // PACKAGES_CAMERA_CAMERA_ELINUX_CAMERA_METHOD_CHANNEL_METHOD_CHANNEL_CAMERA_H_