QT assistant 中有关QHttp的说明，建议我们使用 QNetworkAccessManager 和 QNetworkReply 而非QHttp，因为前者的API更多，并且提供了更丰富的错误处理。

    下面是利用QNetworkAccessManager 和 QNetworkReply 实现的一个http下载类，由于QNetworkAccessManager里面没有提供网络连接中断和超时的错误处理，所以中间我用了QTimer来进行这个容错处理。

    下面代码里，如果发现在下载过程中网络中断，我将重新下载 所有文件 ，并且永不停悉。（maybe it's not used for u, u can comment that）.

Head file:

#ifndef IHTTPDOWNLOADS_H

#define IHTTPDOWNLOADS_H

#include <QObject>

#include <QNetworkAccessManager>

#include <QUrl>

#include <QFile>

#include <QNetworkReply>

#include <QTimer>

#include <QProgressBar>

class iHttpDownloadS : public QObject

{

Q_OBJECT

public:

    explicit iHttpDownloadS(QObject *parent = 0, QProgressBar *_progressBar = 0);

    ~iHttpDownloadS();

    bool    getFileFromURL(const QUrl &url, const QString &filePath); /* get file from url which we need to download, and restore to filePath */

    const QString &getLastErrorMessage(); /* if error occurs, use this to get the error message */

    void setErrorMessage(const QString &msg); /* set _errMsg */

signals:

public slots:

    void replyFinished(QNetworkReply*); /* download finished */

    void replayDownloadProgress(qint64, qint64); /* downloading... */

    void slotError(QNetworkReply::NetworkError); /* handle error */

    void slotReadyRead();/* ready read */

    void handleTimeOut(); /* handle time out */

private:

    QNetworkAccessManager    *_downloadManager;

    QNetworkReply            *_reply;

    QString _errMsg;

    QFile    _file;

    QProgressBar *_progressBar;

    QTimer        *_timeOut;

    QString _filePath;

    QUrl    _url;

};

#endif // IHTTPDOWNLOADS_H

Implementation file:

 

#include "ihttpdownloads.h"

#include <QDebug>

iHttpDownloadS::iHttpDownloadS(QObject *parent, QProgressBar *bar) :

    QObject(parent), _progressBar(bar)

{

    _downloadManager = new QNetworkAccessManager(this);

    _timeOut = new QTimer(this);

    connect(_downloadManager, SIGNAL(finished(QNetworkReply*)), this, SLOT(replyFinished(QNetworkReply*)));

    connect(_timeOut, SIGNAL(timeout()), this, SLOT(handleTimeOut()));

}

iHttpDownloadS::~iHttpDownloadS()

{

    _reply->deleteLater();

    _downloadManager->deleteLater();

}

bool iHttpDownloadS::getFileFromURL(const QUrl &url, const QString &filePath) /* get file from url which we need to download, and restore to filePath */

{

    /* confirm the url is valid or not */

    if (!url.isValid())

    {

        setErrorMessage(QString("Error:URL has specify a invalid name."));

        return false;

    }

    if (url.scheme() != "http")

    {

        setErrorMessage(QString("Error:URL must start with 'http:'"));

        return false;

    }

    if (url.path().isEmpty())

    {

        setErrorMessage(QString("Error:URL's path is empty."));

        return false;

    }

    if (filePath.isEmpty())

    {

        setErrorMessage(QString("Error:invalid filePath."));

        return false;

    }

    _file.setFileName(filePath);

    if (!_file.open(QIODevice::WriteOnly))

    {

        setErrorMessage(QString("Error:Cannot open file."));

        return false;

    }

    _url = url;

    _filePath = filePath;

    _reply = _downloadManager->get(QNetworkRequest(url));

    connect(_reply, SIGNAL(readyRead()), this, SLOT(slotReadyRead()));

    connect(_reply, SIGNAL(downloadProgress(qint64, qint64)), this, SLOT(replayDownloadProgress(qint64, qint64)));

    connect(_reply, SIGNAL(error(QNetworkReply::NetworkError)), this, SLOT(slotError(QNetworkReply::NetworkError)));

    return true;

}

const QString &iHttpDownloadS::getLastErrorMessage()

{

    return _errMsg;

}

void iHttpDownloadS::setErrorMessage(const QString &msg)

{

    qDebug()<<msg;

    _errMsg = msg;

}

/* slots */

void iHttpDownloadS::handleTimeOut()

{

    qDebug()<<"time out..";

    _timeOut->stop();

    if (_file.isOpen())

    {

        _file.close();

    }

    getFileFromURL(_url, _filePath); /* try again */

}

void iHttpDownloadS::replyFinished(QNetworkReply* reply) /* download finished */

{

    _file.waitForBytesWritten(10000);/* wait 10s for write to file complete, can comment this */

    if (0 == _file.size())

    {

        qDebug()<<"Nothing be downloaded.";

    }

    else

    {

        /* add our updateUI code here... */

        qDebug()<<"finished";

    }

}

void iHttpDownloadS::replayDownloadProgress(qint64 done, qint64 total) /* downloading... */

{

    qDebug()<<QString("%1%").arg(done / (double)total * 100);

    if ((0 != _progressBar) && (0 != total))

    {

        _progressBar->setMaximum(total);

        _progressBar->setValue(done);

    }

}

void iHttpDownloadS::slotReadyRead() /* if this is not been fired for 30s, we trate this timeout, and the timout handle will re download the file */

{

    _file.write(this->_reply->readAll());

    if (_timeOut->isActive())

    {

        _timeOut->stop();

    }

    _timeOut->start(30000);/* wait 30 seconds */

}

void iHttpDownloadS::slotError(QNetworkReply::NetworkError errorCode) /* handle error */

{

    qDebug()<<"error:"<<errorCode;

    setErrorMessage(QString("Error:NetworkError code:%1").arg(errorCode));

    if (_file.isOpen())

    {

        _file.close();

    }

    getFileFromURL(_url, _filePath);/* try again */

}