Qt 4.8 to 5.0 - QPluginLoader->instance returns NULL

Feyh

Hello there,

I've written an Application by using QT 4.8.2. It does dynamically load different plugins to provide multiple functions for the user.
Now Qt5 was released and I wanted to convert my project to the newest version.

I got everything to work, except loading the plugin with QPluginLoader->instance(). While using Qt 4.8.2 it worked fine.

->errorString says:
"The file '.../plugins/nlprod.dll' is not a valid Qt plugin."

That's my code:

PluginLoader.cpp:
@
//"fileName" contains the name of the .dll
pluginLoader->setFileName(pluginsDir->absoluteFilePath(fileName));

    //"a" contains the correct path + name of the .dll
    QString a = pluginLoader->fileName();       

    //"plugin" is null and success "false"
    QObject *plugin = pluginLoader->instance();
    bool success = pluginLoader->isLoaded();

@

MyPlugin.h:
@
class NLPro : public QObject, IConnection
{
Q_OBJECT
Q_PLUGIN_METADATA(IID "NLPro" FILE "nlpro.json") // <- New since I've ported to Qt 5
Q_INTERFACES(IConnection)
...
}
@

MyPlugin.cpp:
I've deleted the following:
@
Q_EXPORT_PLUGIN2(NLPro, NLPro);
@

and I've added a .json-file with the following content:
@
{ "Keys": [ "NLPro"] }
@

Any idea?

Thanks in advance!

Regards