// Copyright (C) 2025 The Qt Company Ltd. // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only /*! \page android-services.html \title Android Services \ingroup android-platform-extra-topics \preliminary \brief Provides information about Android Services support in Qt. \previouspage android-manifest-file-configuration.html \nextpage android-3rdparty-libs.html You can create Android services using Qt. A service is a component that runs in background, so, it has no user interface. It is useful to perform long-term operations such as logging GPS, waiting for social media notifications, and so on. A service will continue to run even if the application that started it exits. \section1 Assemble the Service To get started, create an Android package directory as instructed in \l{Extending Qt with Android Facilities}. This directory contains the \c AndroidManifest.xml file. Inside the package directory, create a \c src directory, where all your Java packages and classes will be created. \section2 Create the Service Class You can create a service by extending the class \c QtService or \l{Android: Service}{Service} to your Java class. Depending on whether you want to use Qt features in your service or call native C++ functions from Java, you need to extend either \c QtService or \c Service. Let's start with a simple service, as follows: \code import android.content.Context; import android.content.Intent; import android.util.Log; import org.qtproject.qt.android.bindings.QtService; public class QtAndroidService extends QtService { private static final String TAG = "QtAndroidService"; @Override public void onCreate() { super.onCreate(); Log.i(TAG, "Creating Service"); } @Override public void onDestroy() { super.onDestroy(); Log.i(TAG, "Destroying Service"); } @Override public int onStartCommand(Intent intent, int flags, int startId) { int ret = super.onStartCommand(intent, flags, startId); // Do some work return ret; } } \endcode \section2 Start the Service Android allows starting services on demand or at boot time. You can do both using Qt as well. \section3 Start a Service On Demand You can start the service in the following ways: \list \li Directly from C++ using \l {QAndroidIntent} and \l {QJniObject}, by creating a service \l {Android: Intent}{Intent} and calling the app's main activity method \l {Android: startService()}{startService()}: \code // Outside of the function body Q_DECLARE_JNI_CLASS(Intent, "android/content/Intent") Q_DECLARE_JNI_CLASS(ComponentName, "android/content/ComponentName") Q_DECLARE_JNI_CLASS(QtAndroidService, "org/qtproject/example/qtandroidservice/QtAndroidService") // Inside function body using namespace QtJniTypes; using namespace QNativeInterface; auto *androidApp = qGuiApp->nativeInterface(); Q_ASSERT(androidApp); Context context = androidApp->context(); QJniEnvironment env; auto serviceClass = env.findClass(Traits::className()); Intent serviceIntent(context, serviceClass); context.callMethod("startService", serviceIntent); \endcode \li Start the service by calling a Java method. The easiest way is to create a static method in your service class: \code public static void startQtAndroidService(Context context) { context.startService(new Intent(context, QtAndroidService.class)); } \endcode Then you can call it from C++ using the following JNI call: \code using namespace QtJniTypes; using namespace QNativeInterface; // ... auto *androidApp = qGuiApp->nativeInterface(); Q_ASSERT(androidApp); Context context = androidApp->context(); QtAndroidService::callStaticMethod("startQtAndroidService", context); \endcode \endlist \section3 Start a Service At Boot Time To run a service at boot time, you need a \l{Android: BroadcastReceiver} {BroadcastReceiver}. Create a custom Java class: \code public class QtBootServiceBroadcastReceiver extends BroadcastReceiver { @Override public void onReceive(Context context, Intent intent) { Intent startServiceIntent = new Intent(context, QtAndroidService.class); context.startService(startServiceIntent); } } \endcode Add the following \c uses-permission in the body of the \c section in the \c AndroidManifest.xml file: \badcode \endcode Also, add the \c receiver definition in the body of the \c section: \badcode \endcode \note Android 8.0 introduced some limitations on running background services, which means using a nomal \c Service class might not work. For more information, see Android's recommendation to use either \l {Android: Foreground services}{Foreground services} or \l {Android: JobIntentService}{JobIntentService}. \section2 Manage the Service in AndroidManifest.xml For the service to be usable in an Android app, you must declare it in the \c AndroidManifest.xml file. Let's start with adding the service section: \list \li When extending \c Service, just declare the service section as a normal Android service. Add the following inside the \c section: \badcode \endcode This way the service will start in the same process as \c QtActivity, which allows you to use native C++ calls from Java code. You can run it in a separate process but that way you cannot use any native calls for communication because the Qt libraries are not loaded for that process. To run on separate process, add this to the service tag: \badcode android:process=":qt_service" \endcode \target Extending QtActivity AndroidManifest.xml \li When extending \c QtService, you need to declare other items for loading all the necessary libs required for Qt, mainly the same items as in \c section for \c QtActivity. Add the following: \badcode \endcode \endlist \note Make sure to define the following to run the service in the background: \badcode \endcode There are a few variations on how to declare services. Some of them are already used in the previous manifest snippet. Depending on your use case, run the service either in the same process as QtActivity or in a separate process. \section3 Service in the Same Process as QtActivity To run a service in the same process as QtActivity, declare the service header as follows: \badcode \endcode \section3 Service in Separate Process To run a service in a dedicated process, declare the service header as follows: \badcode \endcode Qt loads the \c .so file defined in \c android.app.lib_name \c meta-data, and calls the \c main() function with all the arguments set in \c android.app.arguments \c meta-data. When running in a separate process, you can start the service using either the same lib file as the main activity or a separate lib file. \section4 Use the Same .so Lib File Using the same \c .so lib file as the main activity means the service will use the same entry point with an extra argument to distinguish it from the main activity. You can handle your application's execution in the \c main() function according the arguments provided. Add the following argument declaration to your service body: \badcode \endcode Then make sure the service \c android.app.lib_name is the same as the main activity, add the following: \badcode \endcode When using the same \c .so lib file, your application's \c main() function is executed two times, one to start the main activity and the second time to start the service. Thus, you have to handle each execution according to the provided argument. One way to achieve that is as follows: \code if (argc <= 1) { // code to handle main activity execution } else if (argc > 1 && strcmp(argv[1], "-service") == 0) { qDebug() << "Service starting with from the same .so file"; QAndroidService app(argc, argv); return app.exec(); } else { qWarning() << "Unrecognized command line argument"; return -1; } \endcode \section4 Use a Separate .so Lib File In this case, you need to have a sub-project with a \c lib template that provides a different executable for the service. A sample project is: \list \li In CMake: \badcode find_package(Qt6 REQUIRED COMPONENTS Core) qt_add_library(service SHARED servicemessenger.h service_main.cpp ) target_link_libraries(service PRIVATE Qt::Core Qt::CorePrivate ) \endcode \li In qmake: \badcode TEMPLATE = lib TARGET = service CONFIG += dll QT += core core-private SOURCES += \ service_main.cpp HEADERS += servicemessenger.h \endcode \endlist In the \c service_main.cpp you could have the following: \code #include #include #include int main(int argc, char *argv[]) { qWarning() << "Service starting from a separate .so file"; QAndroidService app(argc, argv); return app.exec(); } \endcode Define the \c android.app.lib_name for the service in the \c AndroidManifest.xml: \badcode \endcode \section1 Communication with the Service Qt for Android offers a variety of inter-process communication (IPC) methods to communicate with Android Services. Depending on the structure of your project, you can use either native C++ calls from Java Service or Android BroadcastReceiver. \section2 Native C++ Calls from Java Service This can work with services running in the same process as \c QtActivity and even if \c Service is extended. For more information, see the \l{Qt for Android Notifier}{Qt for Android Notifier Example}. \section2 Using Android BroadcastReceiver \l {Android: BroadcastReceiver}{Android BroadcastReceiver} enables exchanging messages between the Android system, apps, activities and services. Similarly to other Android features, Qt can use broadcast receivers to exchange messages between \c QtActivity and your service. Let's start with logic to send a message from your service. Add the following in your service implementation, which calls \l{Android: sendBroadcast()}{sendBroadcast()}: \code @Override public int onStartCommand(Intent intent, int flags, int startId) { int ret = super.onStartCommand(intent, flags, startId); Intent sendToUiIntent = new Intent(); sendToUiIntent.setAction(ActivityUtils.BROADCAST_CUSTOM_ACTION); sendToUiIntent.putExtra("message", "simple_string"); Log.i(TAG, "Service sending broadcast"); sendBroadcast(sendToUiIntent); return ret; } \endcode Then, you need to create and register the broadcast receiver from the Qt's main activity. The easiest way is to create a custom class with a method and implement all that logic in Java. In the following example, the service sends a message \c "simple_string" to Qt by calling the native method \c sendToQt(): \code public class ServiceBroadcastUtils { private static native void sendToQt(String message); private static final String TAG = "ActivityUtils"; public static final String BROADCAST_CUSTOM_ACTION = "org.qtproject.example.qtandroidservice.broadcast.custom"; public void registerServiceBroadcastReceiver(Context context) { IntentFilter intentFilter = new IntentFilter(); intentFilter.addAction(BROADCAST_CUSTOM_ACTION); context.registerReceiver(serviceMessageReceiver, intentFilter); Log.i(TAG, "Registered broadcast receiver"); } private BroadcastReceiver serviceMessageReceiver = new BroadcastReceiver() { @Override public void onReceive(Context context, Intent intent) { Log.i(TAG, "In OnReceive()"); if (BROADCAST_CUSTOM_ACTION.equals(intent.getAction())) { String message = intent.getStringExtra("message"); sendToQt(message); Log.i(TAG, "Service sent back message to C++: " + message); } } }; } \endcode To make use of all that, start your service as shown in \l{Start the Service}, an then register the broadcast receiver by calling the method \c registerServiceBroadcastReceiver(): \code QJniEnvironment env; jclass javaClass = env.findClass("org/qtproject/example/qtandroidservice/ActivityUtils"); QJniObject classObject(javaClass); const QJniObject context(QNativeInterface::QAndroidApplication::context()); classObject.callMethod("registerServiceBroadcastReceiver", "(Landroid/content/Context;)V", context.object()); \endcode \section2 Using Qt Remote Objects \l{Getting Started with Qt Remote Objects}{Qt Remote Objects} offers an easy way to share APIs between Qt processes. The main concept is to server in the service process, and have a replica in the Qt application, then those two parts are able to exchange data between each other, using signals and slots. \section3 Prepare the replica Let's consider a service example with separate \c .so lib file. Define a \c .rep file which defines our communication class: \code class ServiceMessenger { SLOT(void ping(const QString &message)); SIGNAL(pong(const QString &message)); } \endcode The define the class in the service sub-project as \c servicemessenger.h: \code #include "rep_servicemessenger_source.h" class ServiceMessenger : public ServiceMessengerSource { public slots: void ping(const QString &name) override { emit pong("Hello " + name); } }; \endcode Then, add the \c .rep file to both the main application and service in the main application. \list \li In CMake: \badcode find_package(Qt6 REQUIRED COMPONENTS RemoteObjects) qt_add_repc_replicas(service ../servicemessenger.rep ) target_link_libraries(service PRIVATE Qt6::RemoteObjects) \endcode \li In qmake: \badcode QT += remoteobjects REPC_REPLICA += servicemessenger.rep \endcode \endlist And in the service sub-project: \list \li In CMake: \badcode find_package(Qt6 REQUIRED COMPONENTS RemoteObjects) qt_add_repc_sources(service ../servicemessenger.rep ) target_link_libraries(service PRIVATE Qt6::RemoteObjects) \endcode \li In qmake: \badcode QT += remoteobjects REPC_SOURCE += servicemessenger.rep \endcode \endlist \section3 Connect the source and replica Define the Qt Remote Objects source node in the service sub-project's \c main() function: \code #include "servicemessenger.h" #include #include #include int main(int argc, char *argv[]) { qWarning() << "QtAndroidService starting from separate .so"; QAndroidService app(argc, argv); QRemoteObjectHost srcNode(QUrl(QStringLiteral("local:replica"))); ServiceMessenger serviceMessenger; srcNode.enableRemoting(&serviceMessenger); return app.exec(); } \endcode Then, in the application's \c main() function, connect to source node: \code QRemoteObjectNode repNode; repNode.connectToNode(QUrl(QStringLiteral("local:replica"))); QSharedPointer rep(repNode.acquire()); bool res = rep->waitForSource(); Q_ASSERT(res); QObject::connect(rep.data(), &ServiceMessengerReplica::pong, [](const QString &message){ qDebug() << "Service sent: " << message; }); rep->ping("Qt and Android are friends!"); \endcode This example sends a message from the main application's process to the service. The service replies with the same message, which is printed on the debug logcat. \note The same method could be used when using the same \c .so lib file. For more information, see \l{Use the same .so Lib File}. \section2 Using QAndroidBinder QAndroidBinder is a convenience class that enables inter-process communication by implementing the most important methods in \l {Android: Binder}{Binder}. It allows sending \l{QByteArray} or \l{QVariant} objects between processes. \note Qt for Android has a limitation forcing the execution of only one service at a time when running multiple services in one process. Thus, it is recommended to run each service in its own process. For more information, see \l{QTBUG-78009}. */