main函数中的QCoreAppliaciton a(argc,argv);改成QApplication a(argc,argv);
参考于:Error: QWidget: Cannot create a QWidget without QApplication_lsxpu的专栏-CSDN博客
main函数中的QCoreAppliaciton a(argc,argv);改成QApplication a(argc,argv);
参考于:Error: QWidget: Cannot create a QWidget without QApplication_lsxpu的专栏-CSDN博客