qt 调用窗口 mainwindow.cpp:9:78: error: incomplete type 'QDialog' named in nested name specifier qwindowdefs.h:55:7: note: forward declaration of 'QDialog'

mainwindow.cpp:9:78: error: incomplete type 'QDialog' named in nested name specifier
qwindowdefs.h:55:7: note: forward declaration of 'QDialog'

 

头文件：

DialogSetting *m_SerialSetting = nullptr;

构造函数：

 m_SerialSetting = new DialogSetting(this); //要实例化

    connect(ui->action_serial_setting, &QAction::triggered,m_SerialSetting, &QDialog::show);//error: incomplete type 'QDialog' named in nested name specifier qwindowdefs.h:55:7: note: forward declaration of 'QDialog'