ServiceBrowser Class Implementation
ServiceBrowser::ServiceBrowser(QWidget *parent, Qt::WindowFlags flags)
: QWidget(parent, flags)
{
serviceManager = new QServiceManager(this);
registerExampleServices();
initWidgets();
reloadServicesList();
setWindowTitle(tr("Services Browser"));
}
The constructor registers the "FileManagerService" and "BluetoothTransferService" services that are provided by the filemanagerplugin and bluetoothtransferplugin projects in the examples/ directory. It also calls reloadServicesList() to show these two newly registered services in the top-left pane.
void ServiceBrowser::reloadServicesList()
{
servicesListWidget->clear();
QStringList services = serviceManager->findServices();
for (int i=0; i<services.count(); i++)
servicesListWidget->addItem(services[i]);
servicesListWidget->addItem(showAllServicesItem);
}
When the services list in the top-left pane needs to be refreshed, we call QServiceManager::findServices() to get a QStringList of all services that are currently registered with the service framework.
void ServiceBrowser::reloadInterfaceImplementationsList()
{
...
...
QList<QServiceInterfaceDescriptor> descriptors = serviceManager->findInterfaces(serviceName);
interfacesListWidget->clear();
for (int i=0; i<descriptors.count(); i++) {
QString text = QString("%1 %2.%3")
.arg(descriptors[i].interfaceName())
.arg(descriptors[i].majorVersion())
.arg(descriptors[i].minorVersion());
if (serviceName.isEmpty())
text += " (" + descriptors[i].serviceName() + ")";
QServiceInterfaceDescriptor defaultInterfaceImpl =
serviceManager->interfaceDefault(descriptors[i].interfaceName());
if (descriptors[i] == defaultInterfaceImpl)
text += tr(" (default)");
QListWidgetItem *item = new QListWidgetItem(text);
item->setData(Qt::UserRole, qVariantFromValue(descriptors[i]));
interfacesListWidget->addItem(item);
}
...
}
To create the list of interface implementations in the bottom-left pane, we call QServiceManager::findInterfaces() to get a list of QServiceInterfaceDescriptor objects. If a particular service has been selected in the top-left pane, we call QServiceManager::findInterfaces() with the name of that service as the argument, so that it will only return the interface implementations provided by that service. Otherwise, it is called with no argument to retrieve a list of all implementations provided by all registered services.
The example maps each entry in the interface implementations list to its corresponding QServiceInterfaceDescriptor object using the QListWidgetItem::setData() method.
Note how we also call QServiceManager::defaultServiceInterface() to determine whether an interface implementation is the default for that interface.
void ServiceBrowser::reloadAttributesList()
{
QListWidgetItem *item = interfacesListWidget->currentItem();
if (!item)
return;
QServiceInterfaceDescriptor selectedImpl =
item->data(Qt::UserRole).value<QServiceInterfaceDescriptor>();
QObject *implementationRef;
if (selectedImplRadioButton->isChecked())
implementationRef = serviceManager->loadInterface(selectedImpl, 0, 0);
else
implementationRef = serviceManager->loadInterface(selectedImpl.interfaceName(), 0, 0);
...
The reloadAttributesList() method creates the list in the right-hand pane that shows the attributes of an interface implementation that can be invoked through the Qt meta-object system.
QServiceManager::loadInterface() is called to get an instance of the identified interface implementation. This method finds the corresponding service plugin and returns the QObject instance provided by the service plugin's QServicePluginInterface::createInstance() method.
...
const QMetaObject *metaObject = implementationRef->metaObject();
attributesGroup->setTitle(tr("Invokable attributes for %1 class")
.arg(QString(metaObject->className())));
for (int i=0; i<metaObject->methodCount(); i++) {
QMetaMethod method = metaObject->method(i);
attributesListWidget->addItem("[METHOD] " + QString(method.signature()));
}
for (int i=0; i<metaObject->propertyCount(); i++) {
QMetaProperty property = metaObject->property(i);
attributesListWidget->addItem("[PROPERTY] " + QString(property.name()));
}
}
Call QObject::metaObject() on the implementation instance to get a QMetaObject instance that reveals the dynamically invokable attributes for the instance. These attributes include properties, signals, slots, and methods marked with the Q_INVOKABLE macro. Call QMetaObject::method() to get information about a signal, slot or invokable method, and QMetaObject::property() to access a property of the instance.
When you know the name of the method you wish to invoke, call QMetaObject::invoke() or QMetaMethod::invoke() to invoke it dynamically. Similarly, QMetaProperty::read() and QMetaProperty::write() can be used to read and modify the value of a property.
Invoking attributes: an example
Here is an example of invoking attributes on an implementation, using the FileManagerPlugin that is shown in the Service Browser.
The FileManagerPlugin provides a service called "FileManagerService" in its filemanagerplugin.xml service definition. When FileManagerPlugin::createInstance() is called, if the com.nokia.qt.examples.FileStorage interface is requested, it returns an instance of the FileManagerStorage class. The FileManagerStorage class is defined like this:
class FileManagerStorage : public QObject
{
Q_OBJECT
Q_PROPERTY(QString workingDirectory READ workingDirectory WRITE setWorkingDirectory)
public:
FileManagerStorage(QObject *parent = 0);
void setWorkingDirectory(const QString &path);
QString workingDirectory() const;
signals:
void workingDirectoryChanged(const QString &newDir);
public slots:
void copyFile(const QString ¤tPath, const QString &newPath);
private:
QString directory;
};
So if, in the ServiceBrowser application, we select the com.nokia.qt.examples.FileStorage implementation provided by FileManagerService, the browser would display all the dynamically invokable attributes of the FileManagerStorage class:
As you can see, the FileManagerStorage::workingDirectory property, the FileManagerStorage::copyFile() slot and the FileManagerStorage::workingDirectoryChanged() signal are all listed. (The destroyed(), deleteLater() and _q_reregisterTimers() attributes are inherited from the QObject parent.)
To invoke the copyFile() slot, for example:
QObject *interfaceImpl = QServiceManager::loadInterface("com.nokia.qt.examples.FileStorage", 0, 0);
QMetaObject::invokeMethod(interfaceImpl, "copyFile",
Q_ARG(QString, "path/to/file.txt"),
Q_ARG(QString, "new/path/to/file.txt"));
Of course, the QServiceManager::loadInterface() call here assumes the FileManagerStorage implementation is the default for the com.nokia.qt.examples.FileStorage interface. Otherwise, it would have to pass a QServiceInterfaceDescriptor object to QServiceManager::loadInterface() instead of just the interface name to ensure the correct implementation is loaded.
