How to deal with "QPixmap: Must construct a QGuiApplication before a QPixmap"

jsulm

@laozeng1982 said in How to deal with "QPixmap: Must construct a QGuiApplication before a QPixmap":

QLibrary mylib("CarnacPlotQt5.dll");
if(mylib.load())

Why are you doing this?!
Your application already links against this DLL, there is no need to dynamically load it...

laozeng1982

@jsulm Yes, I just test it, but without this test, it still raise the same error.

J.Hilk

@laozeng1982 assuming you don't have any static QPixmaps or so,

move QApplication app(argc, argv); to the top of your main function

laozeng1982

@J-Hilk Hi, I move the "QApplication app(argc, argv);" to the top and remove QLibrary statement.

but It still the same error.

J.Hilk

@laozeng1982 than you have probably somewhere a static QObject

laozeng1982

@J-Hilk So, how Can I found where is the static Object?

If I don't start the module using the 3rd dlls, it will not raise the error, according to the debugger information, it was in the 3rd part dlls, even I found it, I can't modify it.

J.Hilk

@laozeng1982 its a dll, it's dynamically loaded -> load it after your QApplication instance is up and running.

laozeng1982

@J-Hilk Yes, I want to do this, but I am not familiar with QT, I don't know how to do this.

Second thing, do I need to modify my .pro file and remove static libs?

JonB

@J-Hilk said in How to deal with "QPixmap: Must construct a QGuiApplication before a QPixmap":

@laozeng1982 than you have probably somewhere a static QObject

That would have been my initial comment too. But when I looked at the first post in this thread I see

A stack trace showing me code called from some action/checkbox; and
Console output showing code running as far as the app.exec().

Assuming the OP means the error message about "no application" comes at this point how can it stem from a static QObject? That would happen literally at start up.

J.Hilk

@JonB you are correct, maybe its in a different thread

very strange everything hard to tell from afar