[camera] Source code refactoring (#31)

Changes:
* Source code refactoring
* Add temporary code for camera image stream APIs

packages/camera/elinux/channels/event_channel_image_stream.h

@@ -0,0 +1,27 @@
+// 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_CHANNELS_EVENT_CHANNEL_IMAGE_STREAM_H_
+#define PACKAGES_CAMERA_CAMERA_ELINUX_CAMERA_CHANNELS_EVENT_CHANNEL_IMAGE_STREAM_H_
+
+#include <flutter/encodable_value.h>
+#include <flutter/event_channel.h>
+#include <flutter/plugin_registrar.h>
+
+#include <string>
+
+class EventChannelImageStream {
+ public:
+  EventChannelImageStream(flutter::PluginRegistrar* registrar);
+  ~EventChannelImageStream() = default;
+
+  void Send(const int32_t& width, const int32_t& height, const uint8_t* pixels);
+
+ private:
+  std::unique_ptr<flutter::EventChannel<flutter::EncodableValue>> channel_;
+  std::unique_ptr<flutter::EventSink<flutter::EncodableValue>> event_sink_;
+};
+
+#endif  // PACKAGES_CAMERA_CAMERA_ELINUX_CAMERA_CHANNELS_EVENT_CHANNEL_IMAGE_STREAM_H_