Handle App lifecycle in Nearby Connections.

PiperOrigin-RevId: 822749438

connections/c/nc.cc

@@ -840,12 +840,3 @@ void NcSetPhenotypeFlagReader(READER_CONTEXT context,
       context, phenotype_flag_reader);
   nearby::NearbyFlags::GetInstance().SetFlagReader(*kNearbyFlags);
 }
-
-void NcSaveStates(NC_INSTANCE instance) {
-  NcContext* nc_context = GetContext(instance);
-  if (nc_context == nullptr) {
-    return;
-  }
-
-  nc_context->core->SaveStates();
-}

connections/c/nc.h

@@ -196,10 +196,6 @@ NC_API void NcSetCustomSavePath(NC_INSTANCE instance, const NC_DATA* save_path,
 NC_API void NcSetPhenotypeFlagReader(
     READER_CONTEXT context, NC_PHENOTYPE_FLAG_READER phenotype_flag_reader);
 
-// Saves the states of Nearby Connections to preferences. This is used to
-// restore the states when restart the Nearby Connections.
-NC_API void NcSaveStates(NC_INSTANCE instance);
-
 #ifdef __cplusplus
 }  // extern "C"
 #endif  // __cplusplus

connections/core.cc

@@ -207,8 +207,6 @@ void Core::SetCustomSavePath(absl::string_view path, ResultCallback callback) {
   router_->SetCustomSavePath(&client_, path, std::move(callback));
 }
 
-void Core::SaveStates() { client_.SaveClientInfoToPreferences(); }
-
 std::string Core::Dump() { return client_.Dump(); }
 
 // V3

connections/core.h

@@ -258,10 +258,6 @@ class Core {
   // Gets the local endpoint generated by Nearby Connections.
   std::string GetLocalEndpointId() { return client_.GetLocalEndpointId(); }
 
-  // Saves the states of Nearby Connections to preferences. This is used to
-  // restore the states when restart the Nearby Connections.
-  void SaveStates();
-
   std::string Dump();
 
   //******************************* V3 *******************************

connections/implementation/client_proxy.cc

@@ -64,6 +64,7 @@
 #include "internal/platform/error_code_params.h"
 #include "internal/platform/error_code_recorder.h"
 #include "internal/platform/feature_flags.h"
+#include "internal/platform/implementation/app_lifecycle_monitor.h"
 #include "internal/platform/implementation/platform.h"
 #include "internal/platform/implementation/system_clock.h"
 #include "internal/platform/logging.h"
@@ -138,6 +139,19 @@ ClientProxy::ClientProxy(::nearby::analytics::EventLogger* event_logger)
 
   // Load advertising info from preferences.
   LoadClientInfoFromPreferences();
+
+  if (preferences_manager_ != nullptr) {
+    app_lifecycle_monitor_ =
+        api::ImplementationPlatform::CreateAppLifecycleMonitor(
+            [this](api::AppLifecycleMonitor::AppLifecycleState state) {
+              if (state ==
+                      api::AppLifecycleMonitor::AppLifecycleState::kInactive ||
+                  state == api::AppLifecycleMonitor::AppLifecycleState::
+                               kBackground) {
+                SaveClientInfoToPreferences();
+              }
+            });
+  }
 }
 
 ClientProxy::~ClientProxy() { Reset(); }

connections/implementation/client_proxy.h

@@ -45,6 +45,7 @@
 #include "internal/platform/cancelable_alarm.h"
 #include "internal/platform/cancellation_flag.h"
 #include "internal/platform/error_code_recorder.h"
+#include "internal/platform/implementation/app_lifecycle_monitor.h"
 #include "internal/platform/implementation/preferences_manager.h"
 #include "internal/platform/mac_address.h"
 #include "internal/platform/mutex.h"
@@ -541,6 +542,9 @@ class ClientProxy final {
   std::unique_ptr<CancellationFlag> default_cancellation_flag_ =
       std::make_unique<CancellationFlag>(true);
 
+  // An app lifecycle monitor for monitoring the app lifecycle state.
+  std::unique_ptr<api::AppLifecycleMonitor> app_lifecycle_monitor_;
+
   // A preferences manager for storing client-specific preferences.
   std::unique_ptr<nearby::api::PreferencesManager> preferences_manager_;
 

internal/platform/implementation/BUILD

@@ -149,6 +149,7 @@ cc_library(
 cc_library(
     name = "comm",
     hdrs = [
+        "app_lifecycle_monitor.h",
         "awdl.h",
         "ble.h",
         "bluetooth_adapter.h",

internal/platform/implementation/app_lifecycle_monitor.h

@@ -0,0 +1,57 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef THIRD_PARTY_NEARBY_INTERNAL_PLATFORM_IMPLEMENTATION_APP_LIFECYCLE_MONITOR_H_
+#define THIRD_PARTY_NEARBY_INTERNAL_PLATFORM_IMPLEMENTATION_APP_LIFECYCLE_MONITOR_H_
+
+#include <functional>
+#include <utility>
+
+namespace nearby {
+namespace api {
+
+class AppLifecycleMonitor {
+ public:
+  // The state of the app lifecycle. The state transition is kBackground ->
+  // kInactive -> kActive. Foreground is an umbrella term that describes the app
+  // when it is either Inactive or Active.
+  enum class AppLifecycleState {
+    // The app is active when it starts to receive events.
+    kActive,
+    // The app is inactive but is still not in background.
+    kInactive,
+    // The app is background.
+    kBackground,
+  };
+
+  // Registers callbacks for connection changes. The callbacks will be called
+  // when device is connected to a LAN network or when the device is connected
+  // to internet.
+  explicit AppLifecycleMonitor(
+      std::function<void(AppLifecycleState)> state_updated_callback)
+      : state_updated_callback_(std::move(state_updated_callback)) {}
+
+  virtual ~AppLifecycleMonitor() = default;
+
+ protected:
+  // The callback to be called when the app lifecycle state is updated. In
+  // order to make it possible to be called from different methods, use
+  // std::function instead of absl::AnyInvocable.
+  std::function<void(AppLifecycleState)> state_updated_callback_;
+};
+
+}  // namespace api
+}  // namespace nearby
+
+#endif  // THIRD_PARTY_NEARBY_INTERNAL_PLATFORM_IMPLEMENTATION_APP_LIFECYCLE_MONITOR_H_

internal/platform/implementation/apple/BUILD

@@ -82,6 +82,7 @@ objc_library(
         ":Platform_cc",
         ":Shared",
         ":ble_v2",
+        ":app_lifecycle_monitor",
         ":network_utils",
         # Required Reason API File: third_party/nearby/internal/platform/implementation/apple/preferences_manager.mm
         "//releasetools/apple/privacy/privacymanifests/requiredreasonsapi:user_defaults-user_defaults-read_write_app_data_ca92_1",
@@ -115,6 +116,38 @@ objc_library(
     }),
 )
 
+objc_library(
+    name = "GNCNotificationCenter",
+    hdrs = ["GNCNotificationCenter.h"],
+    deps = [
+        "//third_party/apple_frameworks:Foundation",
+    ],
+)
+
+objc_library(
+    name = "app_lifecycle_monitor",
+    srcs = [
+        "app_lifecycle_monitor.mm",
+    ],
+    hdrs = [
+        "app_lifecycle_monitor.h",
+    ],
+    # Prevent Objective-C++ headers from being pulled into swift.
+    aspect_hints = ["//tools/build_defs/swift:no_module"],
+    deps = [
+        ":GNCNotificationCenter",
+        "//internal/platform:base",
+        "//internal/platform/implementation:comm",
+        "//internal/platform/implementation/apple/Log:GNCLogger",
+        "//third_party/apple_frameworks:Foundation",
+    ] + select({
+        "@platforms//os:platform_ios": [
+            "//third_party/apple_frameworks:UIKit",
+        ],
+        "//conditions:default": [],
+    }),
+)
+
 objc_library(
     name = "ble_v2",
     srcs = [

internal/platform/implementation/apple/GNCNotificationCenter.h

@@ -0,0 +1,40 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef THIRD_PARTY_NEARBY_INTERNAL_PLATFORM_IMPLEMENTATION_APPLE_GNCNOTIFICATIONCENTER_H_
+#define THIRD_PARTY_NEARBY_INTERNAL_PLATFORM_IMPLEMENTATION_APPLE_GNCNOTIFICATIONCENTER_H_
+
+#import <Foundation/Foundation.h>
+
+@protocol GNCNotificationCenter <NSObject>
+
+// Method for registering an observer
+- (id<NSObject>)addObserverForName:(NSNotificationName)name
+                            object:(id)obj
+                             queue:(NSOperationQueue *)queue
+                        usingBlock:(void (^)(NSNotification *notification))block;
+
+// Method for unregistering an observer
+- (void)removeObserver:(id)observer;
+
+// Method for posting a notification
+- (void)postNotificationName:(NSNotificationName)aName
+                      object:(nullable id)anObject;
+
+@end
+
+@interface NSNotificationCenter () <GNCNotificationCenter>
+@end
+
+#endif  // THIRD_PARTY_NEARBY_INTERNAL_PLATFORM_IMPLEMENTATION_APPLE_GNCNOTIFICATIONCENTER_H_

internal/platform/implementation/apple/app_lifecycle_monitor.h

@@ -0,0 +1,46 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef THIRD_PARTY_NEARBY_INTERNAL_PLATFORM_IMPLEMENTATION_APPLE_APP_LIFECYCLE_MONITOR_H_
+#define THIRD_PARTY_NEARBY_INTERNAL_PLATFORM_IMPLEMENTATION_APPLE_APP_LIFECYCLE_MONITOR_H_
+
+#import <Foundation/Foundation.h>
+
+#include "internal/platform/implementation/app_lifecycle_monitor.h"
+
+#import "internal/platform/implementation/apple/GNCNotificationCenter.h"
+
+namespace nearby {
+namespace apple {
+
+class AppLifecycleMonitor : public api::AppLifecycleMonitor {
+ public:
+  explicit AppLifecycleMonitor(std::function<void(AppLifecycleState)> state_updated_callback);
+
+  // Test only.
+  AppLifecycleMonitor(id<GNCNotificationCenter> notification_center,
+                      std::function<void(AppLifecycleState)> state_updated_callback);
+  ~AppLifecycleMonitor() override;
+
+ private:
+  id<GNCNotificationCenter> notification_center_ = nil;
+  id<NSObject> active_observer_ = nil;
+  id<NSObject> inactive_observer_ = nil;
+  id<NSObject> background_observer_ = nil;
+};
+
+}  // namespace apple
+}  // namespace nearby
+
+#endif  // THIRD_PARTY_NEARBY_INTERNAL_PLATFORM_IMPLEMENTATION_APPLE_APP_LIFECYCLE_MONITOR_H_

internal/platform/implementation/apple/app_lifecycle_monitor.mm

@@ -0,0 +1,95 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "internal/platform/implementation/apple/app_lifecycle_monitor.h"
+
+#import <Foundation/Foundation.h>
+
+#include <utility>
+
+#if TARGET_OS_IPHONE
+#import <UIKit/UIKit.h>
+#endif  // TARGET_OS_IPHONE
+
+#import "internal/platform/implementation/apple/GNCNotificationCenter.h"
+#import "internal/platform/implementation/apple/Log/GNCLogger.h"
+
+namespace nearby {
+namespace apple {
+
+AppLifecycleMonitor::AppLifecycleMonitor(
+    std::function<void(AppLifecycleState)> state_updated_callback)
+    : AppLifecycleMonitor([NSNotificationCenter defaultCenter], std::move(state_updated_callback)) {
+}
+
+AppLifecycleMonitor::AppLifecycleMonitor(
+    id<GNCNotificationCenter> notification_center,
+    std::function<void(AppLifecycleState)> state_updated_callback)
+    : api::AppLifecycleMonitor(std::move(state_updated_callback)),
+      notification_center_(notification_center) {
+  // Copy the callback to be captured by the blocks below. This avoids capturing `this` in the
+  // blocks, which would lead to a dangling pointer if `this` is destroyed. The block will hold a
+  // copy of the callback.
+  std::function<void(AppLifecycleState)> callback = state_updated_callback_;
+#if TARGET_OS_IPHONE
+  // Register for app lifecycle notifications
+  background_observer_ =
+      [notification_center_ addObserverForName:UIApplicationDidEnterBackgroundNotification
+                                        object:nil
+                                         queue:nil
+                                    usingBlock:^(NSNotification *notification) {
+                                      GNCLoggerDebug(@"AppLifecycleMonitor: Did enter background.");
+                                      if (callback) {
+                                        callback(AppLifecycleState::kBackground);
+                                      }
+                                    }];
+
+  inactive_observer_ =
+      [notification_center_ addObserverForName:UIApplicationWillResignActiveNotification
+                                        object:nil
+                                         queue:nil
+                                    usingBlock:^(NSNotification *notification) {
+                                      GNCLoggerDebug(@"AppLifecycleMonitor: Will enter inactive.");
+                                      if (callback) {
+                                        callback(AppLifecycleState::kInactive);
+                                      }
+                                    }];
+
+  active_observer_ =
+      [notification_center_ addObserverForName:UIApplicationDidBecomeActiveNotification
+                                        object:nil
+                                         queue:nil
+                                    usingBlock:^(NSNotification *notification) {
+                                      GNCLoggerDebug(@"AppLifecycleMonitor: Will enter active.");
+                                      if (callback) {
+                                        callback(AppLifecycleState::kActive);
+                                      }
+                                    }];
+#else
+  GNCLoggerError(@"Not implemented");
+#endif  // TARGET_OS_IPHONE
+}
+
+AppLifecycleMonitor::~AppLifecycleMonitor() {
+#if TARGET_OS_IPHONE
+  if (notification_center_) {
+    [notification_center_ removeObserver:background_observer_];
+    [notification_center_ removeObserver:active_observer_];
+    [notification_center_ removeObserver:inactive_observer_];
+  }
+#endif  // TARGET_OS_IPHONE
+}
+
+}  // namespace apple
+}  // namespace nearby

internal/platform/implementation/apple/platform.mm

@@ -16,12 +16,14 @@
 
 #import <Foundation/Foundation.h>
 
+#include <functional>
 #include <memory>
 #include <string>
 
 #include "absl/strings/string_view.h"
 #include "internal/base/files.h"
 #import "internal/platform/implementation/apple/Log/GNCLogger.h"
+#include "internal/platform/implementation/apple/app_lifecycle_monitor.h"
 #include "internal/platform/implementation/apple/atomic_boolean.h"
 #include "internal/platform/implementation/apple/atomic_uint32.h"
 #include "internal/platform/implementation/apple/awdl.h"
@@ -205,6 +207,15 @@ std::unique_ptr<WifiDirectMedium> ImplementationPlatform::CreateWifiDirectMedium
 std::unique_ptr<WebRtcMedium> ImplementationPlatform::CreateWebRtcMedium() { return nullptr; }
 #endif
 
+std::unique_ptr<AppLifecycleMonitor> ImplementationPlatform::CreateAppLifecycleMonitor(
+    std::function<void(AppLifecycleMonitor::AppLifecycleState)> state_updated_callback) {
+#if TARGET_OS_IPHONE
+  return std::make_unique<apple::AppLifecycleMonitor>(std::move(state_updated_callback));
+#else
+  return nullptr;
+#endif
+}
+
 absl::StatusOr<WebResponse> ImplementationPlatform::SendRequest(const WebRequest& requestInfo) {
   NSURL* url = [NSURL URLWithString:@(requestInfo.url.c_str())];
   NSMutableURLRequest* request = [NSMutableURLRequest requestWithURL:url];

internal/platform/implementation/g3/platform.cc

@@ -16,6 +16,7 @@
 
 #include <cstddef>
 #include <cstdint>
+#include <functional>
 #include <memory>
 #include <string>
 
@@ -26,6 +27,7 @@
 #include "absl/strings/string_view.h"
 #include "internal/base/file_path.h"
 #include "internal/base/files.h"
+#include "internal/platform/implementation/app_lifecycle_monitor.h"
 #include "internal/platform/implementation/atomic_boolean.h"
 #include "internal/platform/implementation/atomic_reference.h"
 #include "internal/platform/implementation/awdl.h"
@@ -184,8 +186,8 @@ ImplementationPlatform::CreateBluetoothClassicMedium(
   return std::make_unique<g3::BluetoothClassicMedium>(adapter);
 }
 
-std::unique_ptr<api::ble::BleMedium>
-ImplementationPlatform::CreateBleMedium(api::BluetoothAdapter& adapter) {
+std::unique_ptr<api::ble::BleMedium> ImplementationPlatform::CreateBleMedium(
+    api::BluetoothAdapter& adapter) {
   return std::make_unique<g3::BleMedium>(
       dynamic_cast<g3::BluetoothAdapter&>(adapter));
 }
@@ -227,6 +229,13 @@ std::unique_ptr<WebRtcMedium> ImplementationPlatform::CreateWebRtcMedium() {
 }
 #endif
 
+std::unique_ptr<AppLifecycleMonitor>
+ImplementationPlatform::CreateAppLifecycleMonitor(
+    std::function<void(AppLifecycleMonitor::AppLifecycleState)>
+        state_updated_callback) {
+  return nullptr;
+}
+
 absl::StatusOr<WebResponse> ImplementationPlatform::SendRequest(
     const api::WebRequest& request) {
   return absl::UnimplementedError("");

internal/platform/implementation/platform.h

@@ -15,12 +15,15 @@
 #ifndef PLATFORM_API_PLATFORM_H_
 #define PLATFORM_API_PLATFORM_H_
 
+#include <cstddef>
 #include <cstdint>
+#include <functional>
 #include <memory>
 #include <string>
 
 #include "absl/status/statusor.h"
 #include "absl/strings/string_view.h"
+#include "internal/platform/implementation/app_lifecycle_monitor.h"
 #include "internal/platform/implementation/atomic_boolean.h"
 #include "internal/platform/implementation/atomic_reference.h"
 #include "internal/platform/implementation/awdl.h"
@@ -138,6 +141,18 @@ class ImplementationPlatform {
   static std::unique_ptr<WebRtcMedium> CreateWebRtcMedium();
 #endif
 
+#if defined(NEARBY_CHROMIUM)
+  static std::unique_ptr<AppLifecycleMonitor> CreateAppLifecycleMonitor(
+      std::function<void(AppLifecycleMonitor::AppLifecycleState)>
+          state_updated_callback) {
+    return nullptr;
+  }
+#else
+  static std::unique_ptr<AppLifecycleMonitor> CreateAppLifecycleMonitor(
+      std::function<void(AppLifecycleMonitor::AppLifecycleState)>
+          state_updated_callback);
+#endif
+
   // Gets HTTP response from remote server.
   //
   // @param request Webrequest
@@ -147,7 +162,12 @@ class ImplementationPlatform {
   //         other cases will return absl Status in error.
   static absl::StatusOr<WebResponse> SendRequest(const WebRequest& request);
 
-#ifndef NEARBY_CHROMIUM
+#if defined(NEARBY_CHROMIUM)
+  static std::unique_ptr<nearby::api::PreferencesManager>
+  CreatePreferencesManager(absl::string_view path) {
+    return nullptr;
+  }
+#else
   static std::unique_ptr<nearby::api::PreferencesManager>
   CreatePreferencesManager(absl::string_view path);
 #endif

internal/platform/implementation/windows/platform.cc

@@ -28,11 +28,13 @@
 #include <algorithm>
 #include <cstddef>
 #include <cstdint>
+#include <functional>
 #include <memory>
 #include <string>
 
 #include "absl/base/attributes.h"
 #include "absl/status/statusor.h"
+#include "internal/platform/implementation/app_lifecycle_monitor.h"
 #undef StrCat  // Remove the Windows macro definition
 #include "absl/strings/str_cat.h"
 #include "absl/strings/string_view.h"
@@ -290,6 +292,13 @@ std::unique_ptr<WebRtcMedium> ImplementationPlatform::CreateWebRtcMedium() {
   return nullptr;
 }
 
+std::unique_ptr<AppLifecycleMonitor>
+ImplementationPlatform::CreateAppLifecycleMonitor(
+    std::function<void(AppLifecycleMonitor::AppLifecycleState)>
+        state_updated_callback) {
+  return nullptr;
+}
+
 absl::StatusOr<WebResponse> ImplementationPlatform::SendRequest(
     const WebRequest& request) {
   windows::HttpLoader http_loader{request};