QUiLoader in Embedded Linux

[Weilly]

Dear Sir,

I make a custom widget plugin and use it in Designer. Also I use QUiLoader to recreate it in Qt Desktop Linux under Ubuntu. All of them work perfect. However, now I want to use QUiLoader to recreate it in Embedded Qt. I always get the following message:
"QFormBuilder was unable to create a custom widget of the class 'MyButton' ; defaulting to base class 'QWidget'.

I am sure that I put my plugin(xxx.so) under the directory where pluginPaths() shows. I use availableWidgets() to confirm "MyButton". And it doen't exist. Is there anything I can check and adjust?

P.S.

1. My Qt version is v4.7.2
2. I build uitools to my Embedded Qt with static by myself

[Weilly]

I have solved this problem when I using shared library.