QQmlEngine ¶

概要 ¶

详细描述 ¶

每个 QML 组件被实例化在 QQmlContext . QQmlContext ‘s are essential for passing data to QML components. In QML, contexts are arranged hierarchically and this hierarchy is managed by the QQmlEngine .

Prior to creating any QML components, an application must have created a QQmlEngine to gain access to a QML context. The following example shows how to create a simple Text item.

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
...
											

In this case, the Text item will be created in the engine’s root context .

另请参阅

QQmlComponent QQmlContext QML 全局对象

class QQmlEngine ( [ p=None ] ) ¶

param p

QObject

创建新的 QQmlEngine 采用给定 parent .

PySide2.QtQml.QQmlEngine. ObjectOwnership ¶

controls whether or not QML automatically destroys the QObject when the corresponding JavaScript object is garbage collected by the engine. The two ownership options are:

常量	描述
QQmlEngine.CppOwnership	The object is owned by C++ code and QML will never delete it. The JavaScript destroy() method cannot be used on these objects. This option is similar to QScriptEngine::QtOwnership.
QQmlEngine.JavaScriptOwnership	The object is owned by JavaScript. When the object is returned to QML as the return value of a method call, QML will track it and delete it if there are no remaining JavaScript references to it and it has no parent() . An object tracked by one QQmlEngine will be deleted during that QQmlEngine ‘s destructor. Thus, JavaScript references between objects with from two different engines will not be valid if one of these engines is deleted. This option is similar to QScriptEngine::ScriptOwnership.

Generally an application doesn’t need to set an object’s ownership explicitly. QML uses a heuristic to set the default ownership. By default, an object that is created by QML has . The exception to this are the root objects created by calling create() or beginCreate() , which have by default. The ownership of these root-level objects is considered to have been transferred to the C++ caller.

Objects not-created by QML have by default. The exception to this are objects returned from C++ method calls; their ownership will be set to . This applies only to explicit invocations of Q_INVOKABLE methods or slots, but not to property getter invocations.

调用 setObjectOwnership() overrides the default ownership heuristic used by QML.

PySide2.QtQml.QQmlEngine. addImageProvider ( id , arg__2 ) ¶

参数

• id – unicode

• arg__2 – QQmlImageProviderBase

设置 provider to use for images requested via the image : url scheme, with host providerId 。 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.

另请参阅

removeImageProvider() QQuickImageProvider QQmlImageProviderBase

PySide2.QtQml.QQmlEngine. addImportPath ( dir ) ¶

参数

dir – unicode

添加 path as a directory where the engine searches for installed modules in a URL-based directory structure.

path may be a local filesystem directory, a Qt Resource path ( :/imports )， Qt Resource url ( qrc:/imports ) 或 URL。

path will be converted into canonical form before it is added to the import path list.

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

另请参阅

setImportPathList() QML 模块

PySide2.QtQml.QQmlEngine. addNamedBundle ( name , fileName ) ¶

参数

• name – unicode

• fileName – unicode

返回类型

bool

PySide2.QtQml.QQmlEngine. addPluginPath ( dir ) ¶

参数

dir – unicode

添加 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() .

另请参阅

setPluginPathList()

PySide2.QtQml.QQmlEngine. baseUrl ( ) ¶

返回类型

QUrl

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 构造函数。

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

另请参阅

setBaseUrl()

PySide2.QtQml.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.

另请参阅

trimComponentCache()

static PySide2.QtQml.QQmlEngine. contextForObject ( arg__1 ) ¶

参数

arg__1 – QObject

返回类型

QQmlContext

返回 QQmlContext 为 object , or 0 if no context has been set.

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

另请参阅

setContextForObject() qmlContext() qmlEngine()

PySide2.QtQml.QQmlEngine. exit ( retCode ) ¶

参数

retCode – int

PySide2.QtQml.QQmlEngine. imageProvider ( id ) ¶

参数

id – unicode

返回类型

QQmlImageProviderBase

Returns the image provider set for providerId if found; otherwise returns None .

另请参阅

QQuickImageProvider

PySide2.QtQml.QQmlEngine. importPathList ( ) ¶

返回类型

字符串列表

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

例如，若 /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 QML2_IMPORT_PATH environment variable, and the builtin Qml2ImportsPath from QLibraryInfo .

另请参阅

addImportPath() setImportPathList()

PySide2.QtQml.QQmlEngine. importPlugin ( filePath , uri , errors ) ¶

参数

• filePath – unicode

• uri – unicode

• errors – QList

返回类型

bool

Imports the plugin named filePath 采用 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 QQmlEngineExtensionPlugin 接口。

PySide2.QtQml.QQmlEngine. incubationController ( ) ¶

返回类型

QQmlIncubationController

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

另请参阅

setIncubationController()

PySide2.QtQml.QQmlEngine. networkAccessManager ( ) ¶

返回类型

QNetworkAccessManager

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

若 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.

另请参阅

setNetworkAccessManagerFactory()

PySide2.QtQml.QQmlEngine. networkAccessManagerFactory ( ) ¶

返回类型

QQmlNetworkAccessManagerFactory

返回当前 QQmlNetworkAccessManagerFactory .

另请参阅

setNetworkAccessManagerFactory()

static PySide2.QtQml.QQmlEngine. objectOwnership ( arg__1 ) ¶

参数

arg__1 – QObject

返回类型

ObjectOwnership

Returns the ownership of object .

另请参阅

setObjectOwnership()

PySide2.QtQml.QQmlEngine. offlineStorageDatabaseFilePath ( databaseName ) ¶

参数

databaseName – unicode

返回类型

unicode

Returns the file path where a 本地存储 database with the identifier databaseName is (or would be) located.

另请参阅

LocalStorage.openDatabaseSync()

PySide2.QtQml.QQmlEngine. offlineStoragePath ( ) ¶

返回类型

unicode

另请参阅

setOfflineStoragePath()

PySide2.QtQml.QQmlEngine. outputWarningsToStandardError ( ) ¶

返回类型

bool

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

默认值为 true。

另请参阅

setOutputWarningsToStandardError()

PySide2.QtQml.QQmlEngine. pluginPathList ( ) ¶

返回类型

字符串列表

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.

另请参阅

addPluginPath() setPluginPathList()

PySide2.QtQml.QQmlEngine. quit ( ) ¶

PySide2.QtQml.QQmlEngine. removeImageProvider ( id ) ¶

参数

id – unicode

Removes the image provider for providerId .

另请参阅

addImageProvider() QQuickImageProvider

PySide2.QtQml.QQmlEngine. retranslate ( ) ¶

Refreshes all binding expressions that use strings marked for translation.

Call this function after you have installed a new translator with installTranslator , to ensure that your user-interface shows up-to-date translations.

注意

Due to a limitation in the implementation, this function refreshes all the engine’s bindings, not only those that use strings marked for translation. This may be optimized in a future release.

PySide2.QtQml.QQmlEngine. rootContext ( ) ¶

返回类型

QQmlContext

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.

PySide2.QtQml.QQmlEngine. setBaseUrl ( arg__1 ) ¶

参数

arg__1 – QUrl

Set the base URL for this engine to url .

另请参阅

baseUrl()

static PySide2.QtQml.QQmlEngine. setContextForObject ( arg__1 , arg__2 ) ¶

参数

• arg__1 – QObject

• arg__2 – QQmlContext

设置 QQmlContext 为 object to context 。若 object already has a context, a warning is output, but the context is not changed.

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

另请参阅

contextForObject()

PySide2.QtQml.QQmlEngine. setImportPathList ( paths ) ¶

参数

paths – 字符串列表

集 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 QML2_IMPORT_PATH environment variable, and the builtin Qml2ImportsPath from QLibraryInfo .

另请参阅

importPathList() addImportPath()

PySide2.QtQml.QQmlEngine. setIncubationController ( arg__1 ) ¶

参数

arg__1 – QQmlIncubationController

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

另请参阅

incubationController()

PySide2.QtQml.QQmlEngine. setNetworkAccessManagerFactory ( arg__1 ) ¶

参数

arg__1 – QQmlNetworkAccessManagerFactory

设置 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.

注意

QQmlEngine does not take ownership of the factory.

另请参阅

networkAccessManagerFactory()

static PySide2.QtQml.QQmlEngine. setObjectOwnership ( arg__1 , arg__2 ) ¶

参数

• arg__1 – QObject

• arg__2 – ObjectOwnership

设置 ownership of object .

另请参阅

objectOwnership()

PySide2.QtQml.QQmlEngine. setOfflineStoragePath ( dir ) ¶

参数

dir – unicode

另请参阅

offlineStoragePath()

PySide2.QtQml.QQmlEngine. setOutputWarningsToStandardError ( arg__1 ) ¶

参数

arg__1 – bool

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

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

默认值为 true。

另请参阅

outputWarningsToStandardError()

PySide2.QtQml.QQmlEngine. setPluginPathList ( paths ) ¶

参数

paths – 字符串列表

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.

另请参阅

pluginPathList() addPluginPath()

PySide2.QtQml.QQmlEngine. setUrlInterceptor ( urlInterceptor ) ¶

参数

urlInterceptor – QQmlAbstractUrlInterceptor

This API is private for 5.1

设置 urlInterceptor to be used when resolving URLs in QML. This also applies to URLs used for loading script files and QML types. This should not be modifed while the engine is loading files, or URL selection may be inconsistent.

PySide2.QtQml.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.

另请参阅

clearComponentCache()

PySide2.QtQml.QQmlEngine. urlInterceptor ( ) ¶

返回类型

QQmlAbstractUrlInterceptor

This API is private for 5.1

返回当前 QQmlAbstractUrlInterceptor . It must not be modified outside the GUI thread.

PySide2.QtQml.QQmlEngine. warnings ( warnings ) ¶

参数

warnings –