QQmlEngine Class

 QQmlEngine engine;
 QQmlComponent component(&engine);
 component.setData("import QtQuick 2.0\nText { text: \"Hello world!\" }", QUrl());
 QQuickItem *item = qobject_cast<QQuickItem *>(component.create());

 //add item to view, etc
 ...

Member Function Documentation

QQmlEngine::QQmlEngine(QObject * parent = 0)

Create a new QQmlEngine with the given parent.

QQmlEngine::~QQmlEngine() [virtual]

Destroys the QQmlEngine.

Any QQmlContext's created on this engine will be invalidated, but not destroyed (unless they are parented to the QQmlEngine object).

void QQmlEngine::addImageProvider(const QString & providerId, QQmlImageProviderBase * provider)

Sets the provider to use for images requested via the image: url scheme, with host providerId. The QQmlEngine takes ownership of provider.

Image providers enable support for pixmap and threaded image requests. See the QQuickImageProvider documentation for details on implementing and using image providers.

All required image providers should be added to the engine before any QML sources files are loaded.

See also removeImageProvider(), QQuickImageProvider, and QQmlImageProviderBase.

void QQmlEngine::addImportPath(const QString & path)

Adds path as a directory where the engine searches for installed modules in a URL-based directory structure. The path may be a local filesystem directory or a URL.

The newly added path will be first in the importPathList().

See also setImportPathList() and QML Modules.

bool QQmlEngine::addNamedBundle(const QString & name, const QString & fileName)

void QQmlEngine::addPluginPath(const QString & path)

Adds path as a directory where the engine searches for native plugins for imported modules (referenced in the qmldir file).

By default, the list contains only ., i.e. the engine searches in the directory of the qmldir file itself.

The newly added path will be first in the pluginPathList().

See also setPluginPathList().

QUrl QQmlEngine::baseUrl() const

Return the base URL for this engine. The base URL is only used to resolve components when a relative URL is passed to the QQmlComponent constructor.

If a base URL has not been explicitly set, this method returns the application's current working directory.

See also setBaseUrl().

void QQmlEngine::clearComponentCache()

Clears the engine's internal component cache.

This function causes the property metadata of all components previously loaded by the engine to be destroyed. All previously loaded components and the property bindings for all extant objects created from those components will cease to function.

This function returns the engine to a state where it does not contain any loaded component data. This may be useful in order to reload a smaller subset of the previous component set, or to load a new version of a previously loaded component.

Once the component cache has been cleared, components must be loaded before any new objects can be created.

See also trimComponentCache().

QQmlContext * QQmlEngine::contextForObject(const QObject * object) [static]

Returns the QQmlContext for the object, or 0 if no context has been set.

When the QQmlEngine instantiates a QObject, the context is set automatically.

See also setContextForObject().

bool QQmlEngine::event(QEvent *) [virtual protected]

QQmlImageProviderBase * QQmlEngine::imageProvider(const QString & providerId) const

Returns the image provider set for providerId.

Returns the provider if it was found; otherwise returns 0.

See also QQuickImageProvider.

QStringList QQmlEngine::importPathList() const

Returns the list of directories where the engine searches for installed modules in a URL-based directory structure.

For example, if /opt/MyApp/lib/imports is in the path, then QML that imports com.mycompany.Feature will cause the QQmlEngine to look in /opt/MyApp/lib/imports/com/mycompany/Feature/ for the components provided by that module. A qmldir file is required for defining the type version mapping and possibly QML extensions plugins.

By default, the list contains the directory of the application executable, paths specified in the QML_IMPORT_PATH environment variable, and the builtin ImportsPath from QLibraryInfo.

See also addImportPath() and setImportPathList().

bool QQmlEngine::importPlugin(const QString & filePath, const QString & uri, QString * errorString)

Imports the plugin named filePath with the uri provided. Returns true if the plugin was successfully imported; otherwise returns false.

On failure and if non-null, *errorString will be set to a message describing the failure.

The plugin has to be a Qt plugin which implements the QQmlExtensionPlugin interface.

bool QQmlEngine::importPlugin(const QString & filePath, const QString & uri, QList<QQmlError> * errors)

Imports the plugin named filePath with the uri provided. Returns true if the plugin was successfully imported; otherwise returns false.

On failure and if non-null, the errors list will have any errors which occurred prepended to it.

The plugin has to be a Qt plugin which implements the QQmlExtensionPlugin interface.

QQmlIncubationController * QQmlEngine::incubationController() const

Returns the currently set incubation controller, or 0 if no controller has been set.

See also setIncubationController().

QNetworkAccessManager * QQmlEngine::networkAccessManager() const

Returns a common QNetworkAccessManager which can be used by any QML element instantiated by this engine.

If a QQmlNetworkAccessManagerFactory has been set and a QNetworkAccessManager has not yet been created, the QQmlNetworkAccessManagerFactory will be used to create the QNetworkAccessManager; otherwise the returned QNetworkAccessManager will have no proxy or cache set.

See also setNetworkAccessManagerFactory().

QQmlNetworkAccessManagerFactory * QQmlEngine::networkAccessManagerFactory() const

Returns the current QQmlNetworkAccessManagerFactory.

See also setNetworkAccessManagerFactory().

ObjectOwnership QQmlEngine::objectOwnership(QObject * object) [static]

Returns the ownership of object.

See also setObjectOwnership().

bool QQmlEngine::outputWarningsToStandardError() const

Returns true if warning messages will be output to stderr in addition to being emitted by the warnings() signal, otherwise false.

The default value is true.

See also setOutputWarningsToStandardError().

QStringList QQmlEngine::pluginPathList() const

Returns the list of directories where the engine searches for native plugins for imported modules (referenced in the qmldir file).

By default, the list contains only ., i.e. the engine searches in the directory of the qmldir file itself.

See also addPluginPath() and setPluginPathList().

void QQmlEngine::quit() [signal]

This signal is emitted when the QML loaded by the engine would like to quit.

void QQmlEngine::removeImageProvider(const QString & providerId)

Removes the image provider for providerId.

See also addImageProvider() and QQuickImageProvider.

QQmlContext * QQmlEngine::rootContext() const

Returns the engine's root context.

The root context is automatically created by the QQmlEngine. Data that should be available to all QML component instances instantiated by the engine should be put in the root context.

Additional data that should only be available to a subset of component instances should be added to sub-contexts parented to the root context.

void QQmlEngine::setBaseUrl(const QUrl & url)

Set the base URL for this engine to url.

See also baseUrl().

void QQmlEngine::setContextForObject(QObject * object, QQmlContext * context) [static]

Sets the QQmlContext for the object to context. If the object already has a context, a warning is output, but the context is not changed.

When the QQmlEngine instantiates a QObject, the context is set automatically.

See also contextForObject().

void QQmlEngine::setImportPathList(const QStringList & paths)

Sets paths as the list of directories where the engine searches for installed modules in a URL-based directory structure.

By default, the list contains the directory of the application executable, paths specified in the QML_IMPORT_PATH environment variable, and the builtin ImportsPath from QLibraryInfo.

See also importPathList() and addImportPath().

void QQmlEngine::setIncubationController(QQmlIncubationController * controller)

Sets the engine's incubation controller. The engine can only have one active controller and it does not take ownership of it.

See also incubationController().

void QQmlEngine::setNetworkAccessManagerFactory(QQmlNetworkAccessManagerFactory * factory)

Sets the factory to use for creating QNetworkAccessManager(s).

QNetworkAccessManager is used for all network access by QML. By implementing a factory it is possible to create custom QNetworkAccessManager with specialized caching, proxy and cookie support.

The factory must be set before executing the engine.

See also networkAccessManagerFactory().

void QQmlEngine::setObjectOwnership(QObject * object, ObjectOwnership ownership) [static]

Sets the ownership of object.

See also objectOwnership().

void QQmlEngine::setOutputWarningsToStandardError(bool enabled)

Set whether warning messages will be output to stderr to enabled.

If enabled is true, any warning messages generated by QML will be output to stderr and emitted by the warnings() signal. If enabled is false, on the warnings() signal will be emitted. This allows applications to handle warning output themselves.

The default value is true.

See also outputWarningsToStandardError().

void QQmlEngine::setPluginPathList(const QStringList & paths)

Sets the list of directories where the engine searches for native plugins for imported modules (referenced in the qmldir file) to paths.

By default, the list contains only ., i.e. the engine searches in the directory of the qmldir file itself.

See also pluginPathList() and addPluginPath().

void QQmlEngine::trimComponentCache()

Trims the engine's internal component cache.

This function causes the property metadata of any loaded components which are not currently in use to be destroyed.

A component is considered to be in use if there are any extant instances of the component itself, any instances of other components that use the component, or any objects instantiated by any of those components.

See also clearComponentCache().

void QQmlEngine::warnings(const QList<QQmlError> & warnings) [signal]

This signal is emitted when warnings messages are generated by QML.

 // first, define the module API provider function (callback).
 static QJSValue *example_qjsvalue_module_api_provider(QQmlEngine *engine, QJSEngine *scriptEngine)
 {
     Q_UNUSED(engine)

     static int seedValue = 5;
     QJSValue example = scriptEngine->newObject();
     example.setProperty("someProperty", seedValue++);
     return example;
 }

 // second, register the module API provider with QML by calling this function in an initialization function.
 ...
 qmlRegisterModuleApi("Qt.example.qjsvalueApi", 1, 0, example_qjsvalue_module_api_provider);
 ...

 import QtQuick 2.0
 import Qt.example.qjsvalueApi 1.0 as ExampleApi
 Item {
     id: root
     property int someValue: ExampleApi.someProperty
 }

 template<typename T, int metaObjectRevision>
 int qmlRegisterRevision(const char *uri, int versionMajor, int versionMinor);

 template<typename T>
 int qmlRegisterType(const char *uri, int versionMajor, int versionMinor, const char *qmlName);

 template<typename T, int metaObjectRevision>
 int qmlRegisterType(const char *uri, int versionMajor, int versionMinor, const char *qmlName);

 #include <QtQml>

 ...

 qmlRegisterType<MySliderItem>("com.mycompany.qmlcomponents", 1, 0, "Slider");

 import com.mycompany.qmlcomponents 1.0

 Slider {
     // ...
 }