QHttp realize breakpoint continuingly

//downloadObject.h#ifndef HTTPGET_H#define HTTPGET_H#include#includeclass QUrl;class downloadObject : public QObject{Q_OBJECTpublic:QHttp * http;downloadObject(QObject *parent = 0);bool getFile(const QUrl &url,const qint64 totalSize);void abort();signals://void explains();void downloadDone();void updateProgressbar(int current, int all);private slots:void httpDone(bool error);void updateProgress(int current,int all);private:QFile file;QHttpResponseHeader *resp;QString localFileName;qint64 beforeSize;qint64 totalSize;};#endif//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////downloadObject.cpp#include#include#include#include "stdio.h"#include "stdlib.h"#include "time.h"#include "downloadObject.h"downloadObject::downloadObject(QObject *parent): QObject(parent){http = new QHttp(this);connect(http, SIGNAL(done(bool)), this, SLOT(httpDone(bool)));connect(http, SIGNAL(dataReadProgress(int,int)),this, SLOT(updateProgress(int,int)));}bool downloadObject::getFile(const QUrl &url,const qint64 totalSizet){if (!url.isValid()) {std::cerr << "Error: Invalid URL" << std::endl;return false;}if (url.scheme() != "http") {std::cerr << "Error: URL must start with 'http:'" << std::endl;return false;}if (url.path().isEmpty()) {std::cerr << "Error: URL has no path" << std::endl;return false;}localFileName = QFileInfo(url.path()).fileName();if (localFileName.isEmpty())localFileName = "httpget.out";file.setFileName(localFileName);qint64 dwSize = 0;totalSize = totalSizet;if(file.exists()){dwSize = file.size();beforeSize = dwSize;}if (!file.open(QIODevice::Append)) {std::cerr << "Error: Cannot write file "<< qPrintable(file.fileName()) << ": "<< qPrintable(file.errorString()) << std::endl;return false;}QHttp::ConnectionMode mode = url.scheme().toLower() == "https" ? QHttp::ConnectionModeHttps : QHttp::ConnectionModeHttp;http->setHost(url.host(), mode, url.port() == -1 ? 0 : url.port());QHttpRequestHeader *header = new QHttpRequestHeader("GET", url.path());header->setValue("Connection", "Keep-Alive");QString str = "bytes=";QString strTemp = QString("%1").arg(dwSize);str+=strTemp;if (dwSize>totalSize){dwSize = totalSize;}str+="-";strTemp = QString("%1").arg(totalSize);str += strTemp;header->setValue("Range", str);strTemp = url.host()+":80";header->setValue("Host", strTemp);//http->request(*header, 0, &file);http->close();return true;}void downloadObject::abort(){http->abort();file.close();}void downloadObject::httpDone(bool error){if (error) {QString sre = http->errorString();std::cerr << "Error: " << qPrintable(http->errorString())<< std::endl;} else {std::cerr << "File downloaded as "<< qPrintable(file.fileName()) << std::endl;}file.close();emit downloadDone();}void downloadObject::updateProgress(int current, int all){if(current<0){current = 0;}if(beforeSize<0){beforeSize = 0;}current = beforeSize+current;emit updateProgressbar(current, totalSize);}//////////////////////////////////////////////////////////////////////////////////////////////////////////qtdownloaddemo.h#ifndef QTDOWNLOADDEMO_H#define QTDOWNLOADDEMO_H#include#include "ui_qtdownloaddemo.h"#include "downloadObject.h"class QtDownloadDemo : public QDialog{Q_OBJECTpublic:QtDownloadDemo(QWidget *parent = 0, Qt::WFlags flags = 0);~QtDownloadDemo();private slots:void Download();void Done();void Stop();void updateDataReadProgress(int bytesRead,int totalbytes);private:Ui::QtDownloadDemoClass ui;downloadObject *downloadobject;qint64 totalSize;};#endif // QTDOWNLOADDEMO_H//////////////////////////////////////////////////////////////////////////////////////////////////////qtdownloaddemo.cpp#include "qtdownloaddemo.h"#include#includeQtDownloadDemo::QtDownloadDemo(QWidget *parent, Qt::WFlags flags): QDialog(parent, flags){ui.setupUi(this);downloadobject = new downloadObject(this);connect(downloadobject, SIGNAL(downloadDone()), this, SLOT(Done()));connect(downloadobject, SIGNAL(updateProgressbar(int,int)), this, SLOT(updateDataReadProgress(int,int)));}QtDownloadDemo::~QtDownloadDemo(){}void QtDownloadDemo::Stop(){downloadobject->abort();}void QtDownloadDemo::Download(){bool ok;QString strUrl = ui.lineEdit->text();totalSize = ui.lineEdit_2->text().toLongLong(&ok, 10);QUrl url(strUrl);downloadobject->getFile(url,totalSize);}void QtDownloadDemo::Done(){QString str = "download complete";QMessageBox::warning(this,"Message",str);}void QtDownloadDemo::updateDataReadProgress(int bytesRead,int totalbytes){ui.progressBar->setMaximum(totalSize);ui.progressBar->setValue(bytesRead);}