QT中难以解决的有关问题

/********************dialog.h****************************/

#include <QApplication>

#include<QWidget>

#include<QtGui>

#include"printtext.h"


class Dialogs : public QWidget

{

    Q_OBJECT

public:

    Dialogs();

private:

    QFrame *frame;

    QPushButton  *button0; 

    QPushButton  *button1;

    QPushButton  *button2;

    QTextEdit    *textEdit;

private slots:

    void slotbutton0();

    void slotbutton1();

    void slotbutton2();

   // void slotbutton3();


};

/********************dialog.cpp****************************/

#include <QApplication>

#include<stdio.h>

#include<unistd.h>

#include <QtGui>

#include"printtext.h"

#include"dialog.h"


QFile file("printer.txt");

int pid;


Dialogs:ialogs( )


{ 

  frame=new QFrame(this);

  button0=new QPushButton(this); 

  button1=new QPushButton(this); 

  button2=new QPushButton(this); 

   frame->setObjectName("myframe");

   frame->resize(320,240); 

   frame->setStyleSheet("QFrame#myframe{border-image:url(images/background.png)}" );


   button0->setGeometry(260,30,50,50);

   button1->setGeometry(260,90,50,50);

   button2->setGeometry(260,150,50,50);


   QIcon icon;

   QPixmap pixmap0("images/Start_amended.png");

   icon.addPixmap(pixmap0);

   button0->setIcon(icon);

   button0->setIconSize(QSize(50,50));

   button0->setFixedSize(pixmap0.size());

   button0->setMask(pixmap0.mask());


   QPixmap pixmap1("images/Stop_amended.png");

   icon.addPixmap(pixmap1);

   button1->setIcon(icon);

   button1->setIconSize(QSize(50,50));

   button1->setFixedSize(pixmap1.size());

   button1->setMask(pixmap1.mask());



   QPixmap pixmap2("images/set.png");

   icon.addPixmap(pixmap2);

   button2->setIcon(icon);

   button2->setIconSize(QSize(50,50));

   button2->setFixedSize(pixmap2.size());

   button2->setMask(pixmap2.mask());


   connect(button0,SIGNAL(clicked()),this,SLOT(slotbutton0()));

   connect(button1,SIGNAL(clicked()),this,SLOT(slotbutton1()));

   connect(button2,SIGNAL(clicked()),this,SLOT(slotbutton2()));

//  connect(button3,SIGNAL(clicked()),this,SLOT(slotbutton3()));


}


void Dialogs::slotbutton0()

{                              

  execlp("sh","sh","hello.sh",NULL);

  pid=getpid();       

}    


void Dialogs::slotbutton1()

{