簡(jiǎn)述

在前面章節(jié)中我們講述了關(guān)于Qt顯示網(wǎng)絡(luò)圖片的內(nèi)容，比較簡(jiǎn)單，因?yàn)閳D片一般都比較小，下載到本地速度比較快，所以基本不需要什么特殊處理，本節(jié)我們主要針對(duì)HTTP實(shí)現(xiàn)上傳/下載進(jìn)行詳細(xì)的講解與分享，包括：用戶認(rèn)證，實(shí)時(shí)獲取下載大小、速度、剩余時(shí)間信息等。

首先看一下即將用到的公式：

文件剩余大小 = 文件總大小 - 文件已下載大小?
平均速度 = 文件已下載大小 / 文件已下載大小所用的時(shí)間?
瞬時(shí)速度 = 每秒下載的文件大小?
剩余時(shí)間 = 文件剩余大小 / 瞬時(shí)速度

下面以下載為例，來實(shí)現(xiàn)一個(gè)文件下載管理器。

簡(jiǎn)述效果QNetworkAccessManager使用轉(zhuǎn)換總結(jié)更多參考

效果

QNetworkAccessManager

DownloadNetworkManager::DownloadNetworkManager(QObject?*parent)
????:?QNetworkAccessManager(parent)
{
????//?獲取當(dāng)前的時(shí)間戳，設(shè)置下載的臨時(shí)文件名稱
????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()
{
????//?終止下載
????if?(m_pReply?!=?NULL)
????{
????????m_pReply->abort();
????????m_pReply->deleteLater();
????}
}

//?設(shè)置URL及消息頭，開始請(qǐng)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)
{
????//?獲取響應(yīng)的信息，狀態(tài)碼為200表示正常
????QVariant?statusCode?=?reply->attribute(QNetworkRequest::HttpStatusCodeAttribute);

????//?無錯(cuò)誤返回
????if?(reply->error()?==?QNetworkReply::NoError)
????{
????????//?重命名臨時(shí)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());
}

//?用戶認(rèn)證
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);
}

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

????emit?fileName(strFileName);

????//?寫文件-形式為追加
????QFile?file(m_strFileName);
????if?(file.open(QIODevice::Append))
????????file.write(m_pReply->readAll());
????file.close();
}

使用

調(diào)用download()接口開始下載，關(guān)聯(lián)downloadProgress信號(hào)和槽，可以實(shí)時(shí)獲取下載大小、速度、剩余時(shí)間等信息。

//?開始下載
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();
}

//?計(jì)算下載大小、速度、剩余時(shí)間
void?MainWindow::downloadProgress(qint64?bytesReceived,?qint64?bytesTotal)
{
????//?總時(shí)間
????int?nTime?=?downloadTime.elapsed();

????//?本次下載所用時(shí)間
????nTime?-=?m_nTime;

????//?下載速度
????double?dBytesSpeed?=?(bytesReceived?*?1000.0)?/?nTime;
????double?dSpeed?=?dBytesSpeed;

????//剩余時(shí)間
????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);

????//?獲取上一次的時(shí)間
????m_nTime?=?nTime;
}

//?下載完成
void?MainWindow::replyFinished(int?statusCode)
{
????m_nStatusCode?=?statusCode;
????QString?strStatus?=?(statusCode?==?200)???QStringLiteral("下載成功")?:?QStringLiteral("下載失敗");
????m_pStatusLabel->setText(strStatus);
}

轉(zhuǎn)換

下面是一些數(shù)據(jù)的格式轉(zhuǎn)換，包括：字節(jié)轉(zhuǎn)KB、MB、GB，速度轉(zhuǎn)KB/S、MB/S、GB/S，秒轉(zhuǎn)*d *h *m *s格式。

//?字節(jié)轉(zhuǎn)KB、MB、GB
QString?size(qint64?bytes)
{
????QString?strUnit;
????double?dSize?=?bytes?*?1.0;
????if?(dSize?<=?0)
????{
????????dSize?=?0.0;
????}
????else?if?(dSize?<?1024)
????{
????????strUnit?=?"Bytes";
????}
????else?if?(dSize?<?1024?*?1024)
????{
????????dSize?/=?1024;
????????strUnit?=?"KB";
????}
????else?if?(dSize?<?1024?*?1024?*?1024)
????{
????????dSize?/=?(1024?*?1024);
????????strUnit?=?"MB";
????}
????else
????{
????????dSize?/=?(1024?*?1024?*?1024);
????????strUnit?=?"GB";
????}

????return?QString("%1?%2").arg(QString::number(dSize,?'f',?2)).arg(strUnit);
}

//?速度轉(zhuǎn)KB/S、MB/S、GB/S
QString?speed(double?speed)
{
????QString?strUnit;
????if?(speed?<=?0)
????{
????????speed?=?0;
????????strUnit?=?"Bytes/S";
????}
????else?if?(speed?<?1024)
????{
????????strUnit?=?"Bytes/S";
????}
????else?if?(speed?<?1024?*?1024)
????{
????????speed?/=?1024;
????????strUnit?=?"KB/S";
????}
????else?if?(speed?<?1024?*?1024?*?1024)
????{
????????speed?/=?(1024?*?1024);
????????strUnit?=?"MB/S";
????}
????else
????{
????????speed?/=?(1024?*?1024?*?1024);
????????strUnit?=?"GB/S";
????}

????QString?strSpeed?=?QString::number(speed,?'f',?2);
????return?QString("%1?%2").arg(strSpeed).arg(strUnit);
}

//?秒轉(zhuǎn)*d?*h?*m?*s
QString?timeFormat(int?seconds)
{
????QString?strValue;
????QString?strSpacing("?");
????if?(seconds?<=?0)
????{
????????strValue?=?QString("%1s").arg(0);
????}
????else?if?(seconds?<?60)
????{
????????strValue?=?QString("%1s").arg(seconds);
????}
????else?if?(seconds?<?60?*?60)
????{
????????int?nMinute?=?seconds?/?60;
????????int?nSecond?=?seconds?-?nMinute?*?60;

????????strValue?=?QString("%1m").arg(nMinute);

????????if?(nSecond?>?0)
????????????strValue?+=?strSpacing?+?QString("%1s").arg(nSecond);
????}
????else?if?(seconds?<?60?*?60?*?24)
????{
????????int?nHour?=?seconds?/?(60?*?60);
????????int?nMinute?=?(seconds?-?nHour?*?60?*?60)?/?60;
????????int?nSecond?=?seconds?-?nHour?*?60?*?60?-?nMinute?*?60;

????????strValue?=?QString("%1h").arg(nHour);

????????if?(nMinute?>?0)
????????????strValue?+=?strSpacing?+?QString("%1m").arg(nMinute);

????????if?(nSecond?>?0)
????????????strValue?+=?strSpacing?+?QString("%1s").arg(nSecond);
????}
????else
????{
????????int?nDay?=?seconds?/?(60?*?60?*?24);
????????int?nHour?=?(seconds?-?nDay?*?60?*?60?*?24)?/?(60?*?60);
????????int?nMinute?=?(seconds?-?nDay?*?60?*?60?*?24?-?nHour?*?60?*?60)?/?60;
????????int?nSecond?=?seconds?-?nDay?*?60?*?60?*?24?-?nHour?*?60?*?60?-?nMinute?*?60;

????????strValue?=?QString("%1d").arg(nDay);

????????if?(nHour?>?0)
????????????strValue?+=?strSpacing?+?QString("%1h").arg(nHour);

????????if?(nMinute?>?0)
????????????strValue?+=?strSpacing?+?QString("%1m").arg(nMinute);

????????if?(nSecond?>?0)
????????????strValue?+=?strSpacing?+?QString("%1s").arg(nSecond);
????}

????return?strValue;
}

總結(jié)

一般來說，我們下載文件到本地，需要設(shè)置一個(gè)臨時(shí)文件名，這里我以時(shí)間戳為名稱外加.tmp來命名，當(dāng)然更嚴(yán)格的最好再加上隨機(jī)數(shù)，這樣基本就不會(huì)出現(xiàn)重名情況。

下載時(shí)，首先判斷本地文件中是否存在與下載文件同名的文件，如果有則刪除，開始下載。當(dāng)下載完成時(shí)，需要對(duì)臨時(shí)文件重新命名。

以上內(nèi)容比較詳細(xì)，介紹了如何進(jìn)行用戶認(rèn)證，如何實(shí)時(shí)獲取下載大小、速度、剩余時(shí)間等信息，后面我們會(huì)針對(duì)斷點(diǎn)續(xù)傳來進(jìn)行詳細(xì)講解，敬請(qǐng)期待！