线程指针不能准确显示，求师傅

线程指针不能正确显示，求师傅
我想自己设计一个类似时间的界面能显示，但

是不能递加显示，我用QTime能够实现，现在想换一种方法，请问有什么办法可以修改代码
这个是线程代码
#include "mythread.h"
#include "ui_mydialog.h"
#include <QtGui/QtGui>

extern int global_sec;
extern int global_min;
extern int global_hour;
extern int flag;

void MyThread::run()
{
     global_min = 59;
     global_hour = 11;
     global_sec = 55;
     while(1)
    {
        global_sec = (global_sec+1)%60;
        if( global_sec == 0)
           {
                global_min = (global_min+1)%60;
                if ( global_min == 0)
                {
                     global_hour = (global_hour+1)%24;
                }
            }
        if( flag == 0)
           {
             qDebug("%d:%d:%d",global_hour,global_min,global_sec);
             ui->sLineEdit->setText(QString::number(global_sec));//我想让他在这里循环显示，怎么修改
        }
        else
            break;
        sleep(1);
     }
}
//.cpp
#include "mydialog.h"
#include "ui_mydialog.h"
#include "mythread.h"
#include <QTimer>

int global_sec;
int global_min;
int global_hour;
int flag = 0;
myDialog::myDialog(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::myDialog)
{
    ui->setupUi(this);
    ui->hLineEdit->setReadOnly(true);
    ui->mLineEdit->setReadOnly(true);
    ui->sLineEdit->setReadOnly(true);

    connect(ui->runButton,SIGNAL(clicked()),this,SLOT(display()));
    connect(ui->runButton,SIGNAL(clicked()),this,SLOT(runclicked()));
    connect(ui->pauseButton,SIGNAL(clicked()),this,SLOT(runpause()));
    connect(ui->clearButton,SIGNAL(clicked()),this,SLOT(runclear()));
}

myDialog::~myDialog()
{
    delete ui;
}
void myDialog::runclicked()
{
    MyThread *mytime = new MyThread;
    mytime->start();
}
void myDialog::display()
{
    ui->hLineEdit->setText(QString::number(global_hour));
    ui->mLineEdit->setText(QString::number(global_min));