Refactor ActivityStatus to not store current activity

base/android/application_status_listener.cc

+// Copyright 2013 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 "base/android/application_status_listener.h"
+
+#include <jni.h>
+
+#include "base/lazy_instance.h"
+#include "base/observer_list_threadsafe.h"
+#include "jni/ApplicationStatus_jni.h"
+
+namespace {
+struct LeakyLazyObserverListTraits :
+    base::internal::LeakyLazyInstanceTraits<
+        ObserverListThreadSafe<base::android::ApplicationStatusListener> > {
+  static ObserverListThreadSafe<base::android::ApplicationStatusListener>*
+      New(void* instance) {
+    ObserverListThreadSafe<base::android::ApplicationStatusListener>* ret =
+        base::internal::LeakyLazyInstanceTraits<ObserverListThreadSafe<
+            base::android::ApplicationStatusListener> >::New(instance);
+    // Leaky.
+    ret->AddRef();
+    return ret;
+  }
+};
+
+base::LazyInstance<ObserverListThreadSafe<
+    base::android::ApplicationStatusListener>,
+        LeakyLazyObserverListTraits> g_observers = LAZY_INSTANCE_INITIALIZER;
+
+} // namespace
+
+namespace base {
+namespace android {
+
+ApplicationStatusListener::ApplicationStatusListener(
+    const ApplicationStatusListener::ApplicationStateChangeCallback& callback)
+    : callback_(callback) {
+  DCHECK(!callback_.is_null());
+  g_observers.Get().AddObserver(this);
+}
+
+ApplicationStatusListener::~ApplicationStatusListener() {
+  g_observers.Get().RemoveObserver(this);
+}
+
+void ApplicationStatusListener::Notify(ApplicationState state) {
+  callback_.Run(state);
+}
+
+// static
+bool ApplicationStatusListener::RegisterBindings(JNIEnv* env) {
+  bool result = RegisterNativesImpl(env);
+  if (result)
+    Java_ApplicationStatus_registerThreadSafeNativeApplicationStateListener(env);
+  return result;
+}
+
+// static
+void ApplicationStatusListener::NotifyApplicationStateChange(
+    ApplicationState state) {
+  g_observers.Get().Notify(&ApplicationStatusListener::Notify, state);
+}
+
+static void OnApplicationStateChange(JNIEnv* env,
+                                     jclass clazz,
+                                     jint new_state) {
+  ApplicationState application_state = static_cast<ApplicationState>(new_state);
+  ApplicationStatusListener::NotifyApplicationStateChange(application_state);
+}
+
+}  // namespace android
+}  // namespace base