效果

QNetworkAccessManager

DownloadNetworkManager::DownloadNetworkManager(QObject *parent)
    : QNetworkAccessManager(parent)
{
    // 获取当前的时间戳，设置下载的临时文件名称
    QDateTime dateTime = QDateTime::currentDateTime();
    QString date = dateTime.toString("yyyy-MM-dd-hh-mm-ss-zzz");
    m_strFileName = QString("E:/%1.tmp").arg(date);

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

DownloadNetworkManager::~DownloadNetworkManager()
{
    // 终止下载
    if (m_pReply != NULL)
    {
        m_pReply->abort();
        m_pReply->deleteLater();
    }
}

// 设置URL及消息头，开始请求
void DownloadNetworkManager::execute()
{
    m_url = QUrl("http://192.168.*.*/download/2.0.0.zip");

    QNetworkRequest request;
    request.setUrl(m_url);
    request.setHeader(QNetworkRequest::ContentTypeHeader, "application/zip");

    connect(this, SIGNAL(authenticationRequired(QNetworkReply *, QAuthenticator *)), this, SLOT(onAuthenticationRequest(QNetworkReply *, QAuthenticator *)));

    m_pReply = get(request);
    connect(m_pReply, SIGNAL(downloadProgress(qint64, qint64)), this, SIGNAL(downloadProgress(qint64, qint64)));
    connect(m_pReply, SIGNAL(readyRead()), this, SLOT(readyRead()));
}

void DownloadNetworkManager::replyFinished(QNetworkReply *reply)
{
    // 获取响应的信息，状态码为200表示正常
    QVariant statusCode = reply->attribute(QNetworkRequest::HttpStatusCodeAttribute);

    // 无错误返回
    if (reply->error() == QNetworkReply::NoError)
    {
        // 重命名临时文件
        QFileInfo fileInfo(m_strFileName);
        QFileInfo newFileInfo = fileInfo.absolutePath() + m_url.fileName();
        QDir dir;
        if (dir.exists(fileInfo.absolutePath()))
        {
            if (newFileInfo.exists())
                newFileInfo.dir().remove(newFileInfo.fileName());
            QFile::rename(m_strFileName, newFileInfo.absoluteFilePath());
        }
    }
    else
    {
        QString strError = reply->errorString();
        qDebug() << "Error:" << strError;
    }

    emit replyFinished(statusCode.toInt());
}

// 用户认证
void DownloadNetworkManager::onAuthenticationRequest(QNetworkReply *reply, QAuthenticator *authenticator)
{
    QByteArray password;
    password.append("123456");
    password = QByteArray::fromBase64(password);

    QString strPassword(password);

    authenticator->setUser("wang");
    authenticator->setPassword(strPassword);
}

// 本地写文件
void DownloadNetworkManager::readyRead()
{
    QFileInfo fileInfo(m_strFileName);
    QFileInfo newFileInfo = fileInfo.absolutePath() + m_url.fileName();
    QString strFileName = newFileInfo.absoluteFilePath();

    emit fileName(strFileName);

    // 写文件-形式为追加
    QFile file(m_strFileName);
    if (file.open(QIODevice::Append))
        file.write(m_pReply->readAll());
    file.close();
}

使用

调用download()接口开始下载，关联downloadProgress信号和槽，可以实时获取下载大小、速度、剩余时间等信息。

// 开始下载
void MainWindow::download()
{
    if (m_pNetworkManager == NULL)
    {
        m_pNetworkManager = new DownloadNetworkManager(this);
        connect(m_pNetworkManager, SIGNAL(downloadProgress(qint64, qint64)), this, SLOT(downloadProgress(qint64, qint64)), Qt::QueuedConnection);
        connect(m_pNetworkManager, SIGNAL(replyFinished(int)), this, SLOT(replyFinished(int)), Qt::QueuedConnection);
        connect(m_pNetworkManager, SIGNAL(fileName(QString)), m_pFileInfoLabel, SLOT(setText(QString)), Qt::QueuedConnection);
    }
    m_pNetworkManager->execute();
    downloadTime.start();
}

// 计算下载大小、速度、剩余时间
void MainWindow::downloadProgress(qint64 bytesReceived, qint64 bytesTotal)
{
    // 总时间
    int nTime = downloadTime.elapsed();

    // 本次下载所用时间
    nTime -= m_nTime;

    // 下载速度
    double dBytesSpeed = (bytesReceived * 1000.0) / nTime;
    double dSpeed = dBytesSpeed;

    //剩余时间
    qint64 leftBytes = (bytesTotal - bytesReceived);
    double dLeftTime = (leftBytes * 1.0) / dBytesSpeed;

    m_pSpeedInfoLabel->setText(speed(dSpeed));
    m_pLeftTimeInfoLabel->setText(timeFormat(qCeil(dLeftTime)));
    m_pFileSizeInfoLabel->setText(size(bytesTotal));
    m_pDownloadInfoLabel->setText(size(bytesReceived));
    m_pProgressBar->setMaximum(bytesTotal);
    m_pProgressBar->setValue(bytesReceived);

    // 获取上一次的时间
    m_nTime = nTime;
}

// 下载完成
void MainWindow::replyFinished(int statusCode)
{
    m_nStatusCode = statusCode;
    QString strStatus = (statusCode == 200) ? QStringLiteral("下载成功") : QStringLiteral("下载失败");
    m_pStatusLabel->setText(strStatus);
}

http://blog.csdn.net/liang19890820/article/details/50814339