How to access qml object from one C++ extensionplugin

csfreebird

I just try the following code in my extensionplugin:
@class QExampleQmlPlugin : public QQmlExtensionPlugin
{
Q_OBJECT
Q_PLUGIN_METADATA(IID "org.qt-project.Qt.QQmlExtensionInterface")

public:

void registerTypes(const char *uri) {
qmlRegisterType<ClickHandler>(uri, 1, 0, "MyClick");
QString str = objectName();
QObject * p = parent();
// QString str2 = p->objectName();
int i = 0;
}

void initializeEngine(QQmlEngine * engine, const char * uri) {
QQmlApplicationEngine* app_engine = qobject_cast<QQmlApplicationEngine*>(engine);
QList<QObject *> roots = app_engine->rootObjects();
int i = 0;
}
};
@

but the roots is empty:
@(gdb) p roots
$1 = {{p = {static shared_null = {ref = {atomic = {_q_value = -1}}, alloc = 0, begin = 0, end = 0, array = {0x0}}, d = 0x7ffff6355da0 QListData::shared_null}, d = 0x7ffff6355da0 QListData::shared_null}}
(gdb) [Thread 0x7fffe2304700 (LWP 19788) exited]@

In my main app project, in main.cpp file, I use QQmlApplicationEngine to load main.qml file, in main.qml file, I load my plugin. Code snippet from main.cpp
@ QQmlApplicationEngine engine;
engine.addImportPath(imports_dir_path);
engine.load(QUrl("qrc:/qmls/main.qml"));

QObject * topLevel = engine.rootObjects().value(0);
QQuickWindow * window = qobject_cast<QQuickWindow*>(topLevel);
if (!window) {
  qWarning("Error: Your root item has to be a Window.");
  return -1;
}
window->showMaximized();
return app->exec&#40;&#41;;@

code from main.qml
@import demo 1.0 // import types from the plugin
import QtQuick.Window 2.1
import QtQuick.Controls 1.1
import QtQuick.XmlListModel 2.0
import QtQuick 2.2

// this class is defined in QML (imports/demo/hello.qml)
Window {
Hello {
// this class is defined in C++ (plugin.cpp)
MyClick {
id: click
}

    Text {
        text: click.value
    }
}

}@

dheerendra

How and where are you calling initializeEngine ?

csfreebird

My class is a sub-class of QQmlExtensionPlugin
initializeEngine is a virtual method inherited from QQmlExtensionPlugin class.
After testing this, I find this method will be called by Qt while my extensionplugin is loaded by qml.