新手求教Qt的初级有关问题，关于创建动作的

新手求教Qt的初级问题，关于创建动作的
头文件

#ifndef MAINWINDOW_COPY_H
#define MAINWINDOW_COPY_H

#include <QMainWindow>

class QAction;
class QLabel;
class Spreadsheet;



class MainWindow_copy : public QMainWindow
{

  Q_OBJECT

public:
  MainWindow_copy();
  Spreadsheet *spreadsheet;

public:
  QMenu *fileMenu;
  QMenu *editMenu;
  QMenu *toolsMenu;
  QMenu *optionsMenu;
  QMenu *helpMenu;
  QLabel *locationLabel;
  QLabel *formulaLabel;
  QToolBar *fileToolBar;
  QToolBar *editToolBar;
  QAction *newAction;


private:
  void createMenus();
  void createStatusBar();
  void createToolBar();
  void createActions();

};

#endif // MAINWINDOW_COPY_H



cpp文件
#include <QMainWindow>
#include <QtGui>
#include <QtGui/QMenuBar>
#include <mainwindow_copy.h>
#include "spreadsheet.h"

MainWindow_copy::MainWindow_copy()
{
createMenus();
spreadsheet = new Spreadsheet;
setCentralWidget(spreadsheet);
createStatusBar();
createToolBar();

}

void MainWindow_copy::createMenus()
{
  fileMenu = menuBar()->addMenu(tr("&File"));
  fileMenu->addAction(newAction);
  editMenu= menuBar()->addMenu(tr("&Edit"));
  toolsMenu = menuBar()->addMenu(tr("&Tools"));
  optionsMenu = menuBar()->addMenu(tr("&Options"));
  helpMenu = menuBar()->addMenu(tr("&Help"));
}

void MainWindow_copy::createStatusBar()
{

locationLabel = new QLabel("W999");
statusBar()->addWidget(locationLabel);
formulaLabel = new QLabel;
statusBar()->addWidget(formulaLabel,1);

}

void MainWindow_copy::createActions()
{
  newAction = new QAction(tr("&New"),this);
  newAction->setShortcut(QKeySequence::New);
  newAction->setIcon(QIcon(":/images/new.png"));
  newAction->setStatusTip("this is a Create new file");
  connect(newAction,SIGNAL(triggered()),this,SLOT(close()));
}

主函数

#include <QApplication>

#include "mainwindow_copy.h"

int main(int argc,char *argv[])
{
  QApplication app(argc,argv);
  MainWindow_copy lxb;
  lxb.show();
  return app.exec();
}


参照经典Qt教程C++ GUI Qt4第三章的例子我想把整个例子再组装一遍，先是创建了窗口，菜单栏，工具栏，还有spreadsheet（上面程序没有包括相关的文件），但是往菜单栏File选项添加动作的时候出现问题了
出现问题的语句： fileMenu->addAction(newAction);
删掉它，窗口正确显示
添上它，提示错误如下：
Starting /home/lxb/qt/mainwindow_copy/mainwindow_copy...
The program has unexpectedly finished.
/home/lxb/qt/mainwindow_copy/mainwindow_copy exited with code 0

我参照示例程序，感觉程序应该没有问题，但是就是报这个错

求高人指点，不胜感激！

------解决方案--------------------

C/C++ code

void MainWindow_copy::createMenus(){  fileMenu = menuBar()->addMenu(tr("&File"));  createActions();//加上这一句，先创建Action啊，不然action都没有，你怎么添加  fileMenu->addAction(newAction);  editMenu= menuBar()->addMenu(tr("&Edit"));  toolsMenu = menuBar()->addMenu(tr("&Tools"));  optionsMenu = menuBar()->addMenu(tr("&Options"));  helpMenu = menuBar()->addMenu(tr("&Help"));}