在对话框窗体构造函数加入

 

SystemDialog::SystemDialog(QWidget *parent) :    QDialog(parent),    ui(new Ui::SystemDialog){    ui->setupUi(this);    Qt::WindowFlags flags=Qt::Dialog;    flags |=Qt::WindowMinimizeButtonHint;    flags |=Qt::WindowMaximizeButtonHint;    flags |=Qt::WindowCloseButtonHint;    setWindowFlags(flags);  }