QMainWindow as a Designer plugin

[waiter]

hello! I make QMainWindow as a Designer plugin,and then I use QUiLoader to load a ui that use the plugin,but the widget can't show,it only show when widget->setWindowFlags(Qt::SubWindow),but it is not aways works,,what should I do !

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Added after 6 minutes:

I subclass the QMainWindow and Make a Qt Designer plugin,,sorry my poor English,,