How to use QDesignerCustomWidgetInterface.registerCustomWidget()

[shadow3d]

Hi there,
I want to design a custom number keyboard and register it to pyside6-designer by registerCustomWidget(), so I can reuse it whenever possible.
I have referred to the example Task Menu Extension Example and the document Custom Widgets in Qt Widgets Designer.
But I still can understand how to do it.
I have already tried:

$ python registertictactoe.py
class QPyDesignerCustomWidgetCollection *__cdecl QPyDesignerCustomWidgetCollection::instance(void): Cannot find QCoreApplication instance.
$ 

I want to know how to realize the following effect:

Is there some step-by-step document that can be referred to?
Thanks

[friedemannkleint]

The key point is setting the environment variable PYSIDE_DESIGNER_PLUGINS as explained in https://doc.qt.io/qtforpython-6/tutorials/basictutorial/uifiles.html#designer-custom-widgets .

[shadow3d]

@friedemannkleint
Thanks for your important information.
Now I can register my custom widget.
However, I want to organize multiple custom widgets gracefully as here: pyside_plugins.
Now the NumKeyboard (first custom widget) delete picture can't display.

I have tried importing the Icon by file or resources, but neither works.
Could you help me, thank you.

[friedemannkleint]

Have you imported the rc_file generated from .qrc? See fex in examples:

import rc_rhiwindow

or similar (see https://doc.qt.io/qtforpython-6/tutorials/basictutorial/qrcfiles.html#tutorial-qrcfiles )

[shadow3d]

@friedemannkleint
Yes, the rc_file is imported automatically by NumKeyboard_ui.py when i use the image from resources,

[shadow3d]

@friedemannkleint
Yes, the rc_file is imported automatically by NumKeyboard_ui.py when I use the image from resources,

Edit:
After I modify the "*_ui.py" generated by pyside6-uic:

# import resources_rc
from . import resources_rc   # change to relative import.

The custom widget works well in Designer.