QDeclarativeExtensionPlugin Class

The QDeclarativeExtensionPlugin class provides an abstract base for custom QML extension plugins. 更多...

头：	#include <QDeclarativeExtensionPlugin>
Since:	Qt 4.7
继承：	QObject

所有成员列表，包括继承成员

公共函数

QDeclarativeExtensionPlugin (QObject * parent = 0)

重实现公共函数

virtual void	initializeEngine (QDeclarativeEngine * engine , const char * uri )
virtual void	registerTypes (const char * uri ) = 0

29 公共函数继承自 QObject

额外继承成员

1 特性继承自 QObject
1 公共槽继承自 QObject
1 信号继承自 QObject
7 静态公共成员继承自 QObject
8 保护函数继承自 QObject

详细描述

The QDeclarativeExtensionPlugin class provides an abstract base for custom QML extension plugins.

QDeclarativeExtensionPlugin is a plugin interface that makes it possible to create QML extensions that can be loaded dynamically into QML applications. These extensions allow custom QML types to be made available to the QML engine.

To write a QML extension plugin:

子类 QDeclarativeExtensionPlugin , implement registerTypes () method to register types using qmlRegisterType (), and export the class using the Q_EXPORT_PLUGIN2 () 宏
Write an appropriate project file for the plugin
创建 qmldir 文件 to describe the plugin

QML extension plugins can be used to provide either application-specific or library-like plugins. Library plugins should limit themselves to registering types, as any manipulation of the engine's root context may cause conflicts or other issues in the library user's code.

An example

Suppose there is a new TimeModel C++ class that should be made available as a new QML element. It provides the current time through hour and minute properties, like this:

class TimeModel : public QObject
{
    Q_OBJECT
    Q_PROPERTY(int hour READ hour NOTIFY timeChanged)
    Q_PROPERTY(int minute READ minute NOTIFY timeChanged)
    ...

To make this class available as a QML type, create a plugin that registers this type with a specific 模块使用 qmlRegisterType (). For this example the plugin module will be named com.nokia.TimeExample (as defined in the project file further below).

class QExampleQmlPlugin : public QDeclarativeExtensionPlugin
{
    Q_OBJECT
public:
    void registerTypes(const char *uri)
    {
        Q_ASSERT(uri == QLatin1String("org.qtproject.TimeExample"));
        qmlRegisterType<TimeModel>(uri, 1, 0, "Time");
    }
};
Q_EXPORT_PLUGIN2(qmlqtimeexampleplugin, QExampleQmlPlugin);

This registers the TimeModel class with the 1.0 version of this plugin library, as a QML type called 时间 。 Q_ASSERT statement ensures the module is imported correctly by any QML components that use this plugin.

The project file defines the project as a plugin library and specifies it should be built into the com/nokia/TimeExample 目录：

TEMPLATE = lib
CONFIG += qt plugin
QT += declarative
DESTDIR = com/nokia/TimeExample
TARGET = qmlqtimeexampleplugin
...

Finally, a qmldir 文件 is required in the com/nokia/TimeExample directory that describes the plugin. This directory includes a Clock.qml file that should be bundled with the plugin, so it needs to be specified in the qmldir 文件：

Once the project is built and installed, the new 时间 element can be used by any QML component that imports the com.nokia.TimeExample 模块：

import org.qtproject.TimeExample 1.0 // import types from the plugin
Clock { // this class is defined in QML (org/qtproject/TimeExample/Clock.qml)
    Time { // this class is defined in C++ (plugin.cpp)
        id: time
    }
    hours: time.hour
    minutes: time.minute
}

The full source code is available in the plugins example .

The 教程：采用 C++ 编写 QML 扩展 also contains a chapter on creating QML plugins.

另请参阅 QDeclarativeEngine::importPlugin () 和如何创建 Qt 插件 .

成员函数文档编制

QDeclarativeExtensionPlugin:: QDeclarativeExtensionPlugin ( QObject * parent = 0)

Constructs a QML extension plugin with the given parent .

Note that this constructor is invoked automatically by the Q_EXPORT_PLUGIN2 () macro, so there is no need for calling it explicitly.

`[虚拟]` void QDeclarativeExtensionPlugin:: initializeEngine ( QDeclarativeEngine * engine , const char * uri )

Initializes the extension from the uri 使用 engine . Here an application plugin might, for example, expose some data or objects to QML, as context properties on the engine's root context.

`[pure virtual]` void QDeclarativeExtensionPlugin:: registerTypes (const char * uri )

Registers the QML types in the given uri . Subclasses should implement this to call qmlRegisterType () for all types which are provided by the extension plugin.

The uri is an identifier for the plugin generated by the QML engine based on the name and path of the extension's plugin library.

内容