Generic Sensor API : Ambient Light Sensor API.

device/sensor/sensor_service.cc

+// Copyright 2016 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.
+
+#include "device/sensor/sensor_service.h"
+
+#include <utility>
+
+#include "base/bind.h"
+#include "base/message_loop/message_loop.h"
+#include "base/single_thread_task_runner.h"
+#include "device/sensor/sensor_impl.h"
+#include "device/sensor/sensor_manager.h"
+
+namespace device {
+
+SensorService::SensorService()
+    : main_thread_task_runner_(base::MessageLoop::current()->task_runner()),
+      update_callback_(
+          base::Bind(&SensorService::NotifyConsumers, base::Unretained(this))),
+      reading_updated_(false),
+      is_shutdown_(false) {
+  callback_list_.set_removal_callback(
+      base::Bind(&SensorService::ConsumersChanged, base::Unretained(this)));
+}
+
+SensorService::~SensorService() {}
+
+SensorService* SensorService::GetInstance() {
+  return base::Singleton<SensorService,
+                         base::LeakySingletonTraits<SensorService>>::get();
+}
+
+std::unique_ptr<SensorService::SensorUpdateSubscription>
+SensorService::AddCallback(const SensorUpdateCallback& callback) {
+  DCHECK(main_thread_task_runner_->BelongsToCurrentThread());
+  DCHECK(!is_shutdown_);
+
+  if (!sensor_fetcher_)
+    sensor_fetcher_ = SensorManager::Create(update_callback_);
+
+  if (callback_list_.empty()) {
+    bool success = sensor_fetcher_->StartListeningSensorChange();
+    // On failure pass the default values back.
+    if (!success)
+      callback.Run(AmbientLightSensorReading());
+  }
+
+  if (reading_updated_) {
+    // Send recent reading to the new callback if already available.
+    callback.Run(reading_);
+  }
+
+  return callback_list_.Add(callback);
+}
+
+void SensorService::ConsumersChanged() {
+  if (is_shutdown_)
+    return;
+
+  if (callback_list_.empty()) {
+    sensor_fetcher_->StopListeningSensorChange();
+    reading_updated_ = false;
+  }
+}
+
+void SensorService::NotifyConsumers(const AmbientLightSensorReading& reading) {
+  DCHECK(!is_shutdown_);
+
+  main_thread_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&SensorService::NotifyConsumersOnMainThread,
+                            base::Unretained(this), reading));
+}
+
+void SensorService::NotifyConsumersOnMainThread(
+    const AmbientLightSensorReading& reading) {
+  DCHECK(main_thread_task_runner_->BelongsToCurrentThread());
+  if (callback_list_.empty())
+    return;
+
+  reading_ = reading;
+  reading_updated_ = true;
+  callback_list_.Notify(reading_);
+}
+
+void SensorService::Shutdown() {
+  if (!callback_list_.empty())
+    sensor_fetcher_->StopListeningSensorChange();
+  sensor_fetcher_.reset();
+  is_shutdown_ = true;
+}
+
+}  // namespace device