提示信息：
QObject::connect: Parentheses expected, signal QAction::triggered in ..
QObject::connect: (receiver name: 'MainWindow')
且槽函数未执行。
原因:信号语句中少了括号（猪心大姨），应该写成
connect(openAct,SIGNAL(triggered()),this,SLOT(open()));
connect(newAct,SIGNAL(triggered()),this,SLOT(newEvent()));