#ifndef HttpDownload_H
#define HttpDownload_H

#include <QNetworkAccessManager>
#include <QUrl>

QT_BEGIN_NAMESPACE
class QFile;
class QNetworkReply;
QT_END_NAMESPACE

class HttpDownload : public QObject
{
    Q_OBJECT

public:
    HttpDownload(QObject *parent = 0);
    void downloadFile(QUrl url);

private slots:
    void startRequest(QUrl url);
    void cancelDownload();
    void httpFinished();
    void httpReadyRead();
    void updateDataReadProgress(qint64 bytesRead, qint64 totalBytes);

private:
    QUrl url;
    QNetworkAccessManager qnam;
    QNetworkReply *reply;
    QFile *file;
    int httpGetId;
    bool httpRequestAborted;
};

#endif

#include <QtNetwork>

#include "HttpDownload.h"

HttpDownload::HttpDownload(QObject *parent) : QObject(parent)
{
}

void HttpDownload::startRequest(QUrl url)
{
    reply = qnam.get(QNetworkRequest(url));
    connect(reply, SIGNAL(finished()),
            this, SLOT(httpFinished()));
    connect(reply, SIGNAL(readyRead()),
            this, SLOT(httpReadyRead()));
    connect(reply, SIGNAL(downloadProgress(qint64,qint64)),
            this, SLOT(updateDataReadProgress(qint64,qint64)));
}

void HttpDownload::downloadFile(QUrl url)
{
    QFileInfo fileInfo(url.path());
    QString fileName = fileInfo.fileName();
    if (QFile::exists(fileName)) {
//        обработка ситуации если файл уже есть
    }

    file = new QFile(fileName);
    if (!file->open(QIODevice::WriteOnly)) {
// если файл нельза записать
        delete file;
        file = 0;
        return;
    }
    httpRequestAborted = false;
    startRequest(url);
}

void HttpDownload::cancelDownload()
{
    httpRequestAborted = true;
    reply->abort();
}

void HttpDownload::httpFinished()
{
    if (httpRequestAborted) {
        if (file) {
            file->close();
            file->remove();
            delete file;
            file = 0;
        }
        reply->deleteLater();
        return;
    }
    file->flush();
    file->close();
    reply->deleteLater();
    reply = 0;
    delete file;
    file = 0;
}

void HttpDownload::httpReadyRead()
{
    if (file)
        file->write(reply->readAll());
}

void HttpDownload::updateDataReadProgress(qint64 bytesRead, qint64 totalBytes)
{
    if (httpRequestAborted)
        return;
// если нужно информируем о прогрессе
}

 #include <QApplication>
#include <QDialog>
#include "HttpDownload.h"

int main(int argc, char *argv[])
{
     QApplication app(argc, argv);
    HttpDownload httpDownload;
    httpDownload.downloadFile(QUrl("http://linuxforum.ru/index.php"));
    QDialog dlg;
    dlg.show();
    return dlg.exec();
}

#include <iostream>
#include <cstdlib>
#include <string>
#include <QtCore>
#include <QApplication>
#include <QDir>
#include <QtNetwork>
#include <QNetworkAccessManager>
#include <QUrl>

QString PChar2String(const char* PChar);
char* String2PChar(const QString String);
int URLDownloadToFile(const QString URL, const QString FileName);

QString CD = PChar2String("");

int main(int ParamCount, char* ParamStr[])
{
    QApplication Application(ParamCount, ParamStr);
    CD = Application.applicationDirPath();
    URLDownloadToFile(PChar2String("http://linuxforum.ru/img/linuxforum_winter.jpg"), PChar2String("/home/user/Documents/linuxforum_winter.jpg"));
    return 0;
}

QString PChar2String(const char* PChar)
{
    return QString("%1").arg(PChar);
}

char* String2PChar(const QString String)
{
    QByteArray Result = String.toAscii();
    return Result.data();
}

int URLDownloadToFile(const QString URL, const QString FileName)
{
    QNetworkAccessManager qnam;
    QNetworkReply* Reply = NULL;
    QFile* File = NULL;
    if (FileName.isEmpty())
        return 1;
    if (QFile::exists(FileName))
        QFile::remove(FileName);
    File = new QFile(FileName);
    if ( !File->open(QIODevice::WriteOnly) ) {
        delete File;
        File->remove();
        return 1;
    }
    Reply = qnam.get(QNetworkRequest(QUrl(URL)));
    if (Reply->error())
    {
        delete File;
        File->remove();
        return 1;
    }
    File->flush();
    if ( File )
        File->write(Reply->readAll());
    File->close();
    delete Reply;
    delete File;
    return 0;
}