QDesignerCustomWidgetCollectionInterface Class▲
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Header: QDesignerCustomWidgetCollectionInterface
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qmake: QT += designer
Detailed Description▲
When implementing a custom widget plugin, you build it as a separate library. If you want to include several custom widget plugins in the same library, you must in addition subclass QDesignerCustomWidgetCollectionInterface.
QDesignerCustomWidgetCollectionInterface contains one single function returning a list of the collection's QDesignerCustomWidgetInterface objects. For example, if you have several custom widgets CustomWidgetOne, CustomWidgetTwo and CustomWidgetThree, the class definition may look like this:
#include customwidgetoneinterface.h
#include customwidgettwointerface.h
#include customwidgetthreeinterface.h
#include <QtDesigner/qtdesigner.h>
#include <QtCore/qplugin.h>
class MyCustomWidgets: public QObject, public QDesignerCustomWidgetCollectionInterface
{
Q_OBJECT
Q_PLUGIN_METADATA(IID "org.qt-project.Qt.QDesignerCustomWidgetCollectionInterface")
Q_INTERFACES(QDesignerCustomWidgetCollectionInterface)
public:
MyCustomWidgets(QObject *parent = 0);
QList<QDesignerCustomWidgetInterface*> customWidgets() const override;
private:
QList<QDesignerCustomWidgetInterface*> widgets;
};In the class constructor you add the interfaces to your custom widgets to the list which you return in the customWidgets() function:
MyCustomWidgets::MyCustomWidgets(QObject *parent)
: QObject(parent)
{
widgets.append(new CustomWidgetOneInterface(this));
widgets.append(new CustomWidgetTwoInterface(this));
widgets.append(new CustomWidgetThreeInterface(this));
}
QList<QDesignerCustomWidgetInterface*> MyCustomWidgets::customWidgets() const
{
return widgets;
}Note that instead of exporting each custom widget plugin using the Q_PLUGIN_METADATA() macro, you export the entire collection. The Q_PLUGIN_METADATA() macro ensures that Qt Designer can access and construct the custom widgets. Without this macro, there is no way for Qt Designer to use them.