Error: QWidget: Cannot create a QWidget without QApplication

参考：

https://blog.csdn.net/lsxpu/article/details/17840231

【1】 解决QWidget: Cannot create a QWidget when no GUI is being used http://blog.csdn.net/muyuyuzhong/article/details/7034301

【2】Qt - QWidget: Cannot create a QWidget when no GUI is being used http://stackoverflow.com/questions/5521752/qt-qwidget-cannot-create-a-qwidget-when-no-gui-is-being-used
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作者：lsxpu 
来源：CSDN 
原文：https://blog.csdn.net/lsxpu/article/details/17840231 
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