Android Service with BroadcastReceiver - Same Lib File

This example demonstrates how to create and run an Android service in its own process using the same main .so lib file, and then exchange data between QML/C++ and the Java service using a BroadcastReceiver.

When clicking the Send to Service button, the name entered in the QML view, Qt, in this case, is sent to the Android service. Then, the service replies back with a message Hello Qt which is printed in the QML view.

Running the Example

To run the example from Qt Creator, open the Welcome mode and select the example from Examples. For more information, visit Building and Running an Example.

Create the Service

When running the app's process, you can extend either QtService or Service. Extending QtService allows Qt to load all the necessary libraries to load Qt components correctly and call native methods on Android. However, here the service is running in the same process, and with the BroadcastReceiver you don't need native calls to exchange messages with Qt, so extending either class works.

Start by creating the Java service class. This is a normal Android Service that receives a name from QML and replies back with Hello <name>:

package org.qtproject.example.qtandroidservice;

import android.content.Context;
import android.content.Intent;
import android.util.Log;
import android.os.IBinder;
import org.qtproject.qt5.android.bindings.QtService;
import android.content.IntentFilter;

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);

        String name = new String(intent.getByteArrayExtra("name"));
        Intent sendToUiIntent = new Intent();
        sendToUiIntent.setAction(ActivityUtils.BROADCAST_NAME_ACTION);
        sendToUiIntent.putExtra("name", name);
        Log.i(TAG, "Service sending broadcast");
        sendBroadcast(sendToUiIntent);

        return ret;
    }

    @Override
    public IBinder onBind(Intent intent) {
        return super.onBind(intent);
    }
}

In the overwritten method onStartCommand(), the service receives a name from the calling intent, then sends a broadcast to the BroadcastReceiver, which in turn will call the native method sendToQt(String message). For more information on managing native calls in Qt, see Calling QML/C++ Functions from Java Code.

Manage the AndroidManifest.xml File

To use the service, it must be declared in the AndroidManifest.xml file:

<service android:process=":qt_service" android:name=".QtAndroidService">

        <!-- Application arguments -->
        <meta-data android:name="android.app.arguments" android:value="-service"/>
        <!-- Application arguments -->

        <meta-data android:name="android.app.lib_name" android:value="-- %%INSERT_APP_LIB_NAME%% --"/>
        <meta-data android:name="android.app.qt_sources_resource_id" android:resource="@array/qt_sources"/>
        <meta-data android:name="android.app.repository" android:value="default"/>
        <meta-data android:name="android.app.qt_libs_resource_id" android:resource="@array/qt_libs"/>
        <meta-data android:name="android.app.bundled_libs_resource_id" android:resource="@array/bundled_libs"/>
        <!-- Deploy Qt libs as part of package -->
        <meta-data android:name="android.app.bundle_local_qt_libs" android:value="-- %%BUNDLE_LOCAL_QT_LIBS%% --"/>

        <!-- Run with local libs -->
        <meta-data android:name="android.app.use_local_qt_libs" android:value="-- %%USE_LOCAL_QT_LIBS%% --"/>
        <meta-data android:name="android.app.libs_prefix" android:value="/data/local/tmp/qt/"/>
        <meta-data android:name="android.app.load_local_libs_resource_id" android:resource="@array/load_local_libs"/>
        <meta-data android:name="android.app.load_local_jars" android:value="-- %%INSERT_LOCAL_JARS%% --"/>
        <meta-data android:name="android.app.static_init_classes" android:value="-- %%INSERT_INIT_CLASSES%% --"/>
        <!-- Run with local libs -->

        <!-- Background running -->
        <meta-data android:name="android.app.background_running" android:value="true"/>
        <!-- Background running -->
    </service>

Start the Service

Since the service is run using the same .so lib file with different arguments for the service, you must handle the arguments. For the main application use:

    if (argc <= 1) {

Then take the following steps:

1. Register the native method
2. Create the BroadcastReceiver in a custom Java class:

   package org.qtproject.example.qtandroidservice;
   
   import android.content.Context;
   import android.content.Intent;
   import android.util.Log;
   import android.content.BroadcastReceiver;
   import android.content.IntentFilter;
   
   public class ActivityUtils {
   
       private static native void sendToQt(String message);
   
       private static final String TAG = "ActivityUtils";
       public static final String BROADCAST_NAME_ACTION = "org.qtproject.example.qtandroidservice.broadcast.name";
   
       public void registerServiceBroadcastReceiver(Context context) {
           IntentFilter intentFilter = new IntentFilter();
           intentFilter.addAction(BROADCAST_NAME_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 broadcast receiver");
               if (BROADCAST_NAME_ACTION.equals(intent.getAction())) {
                   String name = intent.getStringExtra("name");
                   Log.i(TAG, "Service received name: " + name);
                   String message = "Hello " + name;
                   sendToQt(message);
                   Log.i(TAG, "Service sent back message: " + message);
               }
           }
       };
   }

3. Register the BroadcastReceiver:

   void QtAndroidService::registerBroadcastReceiver()
   {
       QAndroidJniEnvironment env;
       jclass javaClass = env.findClass("org/qtproject/example/qtandroidservice/ActivityUtils");
       QAndroidJniObject classObject(javaClass);
   
       classObject.callMethod<void>("registerServiceBroadcastReceiver",
                                    "(Landroid/content/Context;)V",
                                    QtAndroid::androidContext().object());
   }

4. Call the startService() method, as follows:

   void QtAndroidService::sendToService(const QString &name)
   {
       QAndroidIntent serviceIntent(QtAndroid::androidActivity().object(),
                                   "org/qtproject/example/qtandroidservice/QtAndroidService");
       serviceIntent.putExtra("name", name.toUtf8());
       QAndroidJniObject result = QtAndroid::androidActivity().callObjectMethod(
                   "startService",
                   "(Landroid/content/Intent;)Landroid/content/ComponentName;",
                   serviceIntent.handle().object());
   }

   This function is used to start the Service. If the service is already running, it will only send the names without starting a new service instance.

5. Then, you have to add the necessary Connections, as described in Qt JNI Messenger Example.

Handle the service argument as follows:

    } else if (argc > 1 && strcmp(argv[1], "-service") == 0) {
        qWarning() << "Service starting with BroadcastReceiver from same .so file";
        QAndroidService app(argc, argv);

        return app.exec();

Example project @ code.qt.io