The program has unexpectedly finished.请问

The program has unexpectedly finished.请教！
废话我就不多说了，如下：
mainWindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include<QMainWindow>
#include<QAction>
#include<QMenu>
#include<QToolBar>
#include<QTextEdit>
#include<QPlainTextEdit>
class mainWindow:public QMainWindow
{
  Q_OBJECT
public:
  mainWindow();
/*private slots:
  void openSlot();
  void saveSlot();
  void saveAsSlot();
  void newFileSlot();*/
private:
  void createMenus();

  QAction *openAction;
  QAction *saveAction;
  QAction *saveAsAction;
  QAction *newFileAction;
  QAction *exitAction;
  QAction *cutAction;
  QAction *copyAction;
  QAction *pasteAction;
  QAction *about;
  QAction *aboutQt;

  QMenu *fileMenu;
  QMenu *editMenu;
  QMenu *helpMenu;

  QTextEdit *mainTextEdit;
 };

#endif // MAINWINDOW_H

mainWindow.cpp
#include<QtGui>
#include"mainWindow.h"
mainWindow::mainWindow()
{
  mainTextEdit=new QTextEdit;
  setCentralWidget(mainTextEdit);
  resize(300,300);
  createMenus();
}
void mainWindow::createMenus()
{
  fileMenu=menuBar()->addMenu(tr("&File"));
  fileMenu->addAction(newFileAction);
  fileMenu->addAction(openAction);
  fileMenu->addAction(saveAction);
  fileMenu->addAction(saveAsAction);
  fileMenu->addAction(exitAction);

  editMenu=menuBar()->addMenu(tr("&Edit"));
  editMenu->addAction(cutAction);
  editMenu->addAction(copyAction);
  editMenu->addAction(pasteAction);

  helpMenu=menuBar()->addMenu(tr("&Help"));
  helpMenu->addAction(about);
  helpMenu->addAction(aboutQt);
}

main.cpp
#include<QApplication>
#include"mainWindow.h"

int main(int argc,char *argv[])
{
  QApplication app(argc,argv);
  mainWindow mainwindow;
  app.setApplicationName("Text Application");
  mainwindow.show();
  return app.exec();
}
运行：
Starting /home/chengyan/qt/Application-build-desktop/Application...
The program has unexpectedly finished.
/home/chengyan/qt/Application-build-desktop/Application exited with code 0
请教！！！

[解决办法]
你的QAction和QMenu都没有初始化，需要new一个对象。