Qt文件下载工具

在Qt中实现文件下载功能，通常可以通过多种方式来完成，包括使用 QNetworkAccessManager 和 QNetworkReply 类，或者使用更高级别的 QHttpMultiPart 类。以下是两种常见的实现方法：

方法1：使用 QNetworkAccessManager 和 QNetworkReply
创建 QNetworkAccessManager 对象：这个对象负责管理和处理网络请求。

发送 GET 请求：使用 QNetworkAccessManager 的 get 方法来发送一个GET请求到指定的URL。

接收数据：通过重写槽函数 readyRead 来接收数据。

保存文件：将接收到的数据写入到文件中。

处理完成：当下载完成后，重写 finished 槽函数来处理完成的逻辑。
请添加图片描述


#ifndef DOWNLOAD_DIALOG_H
#define DOWNLOAD_DIALOG_H#include <QDir>
#include <QDialog>
#include <ui_Downloader.h>namespace Ui {
class Downloader;
}class QNetworkReply;
class QNetworkAccessManager;/*** \brief Implements an integrated file downloader with a nice UI*/
class Downloader : public QWidget
{Q_OBJECTsignals:void downloadFinished (const QString& url, const QString& filepath);public:explicit Downloader (QWidget* parent = 0);~Downloader();bool useCustomInstallProcedures() const;QString downloadDir() const;void setDownloadDir(const QString& downloadDir);public slots:void setUrlId (const QString& url);void startDownload (const QUrl& url);void setFileName (const QString& file);void setUserAgentString (const QString& agent);void setUseCustomInstallProcedures (const bool custom);private slots:void finished();void openDownload();void installUpdate();void cancelDownload();void saveFile (qint64 received, qint64 total);void calculateSizes (qint64 received, qint64 total);void updateProgress (qint64 received, qint64 total);void calculateTimeRemaining (qint64 received, qint64 total);private:qreal round (const qreal& input);private:QString m_url;uint m_startTime;QDir m_downloadDir;QString m_fileName;Ui::Downloader* m_ui;QNetworkReply* m_reply;QString m_userAgentString;bool m_useCustomProcedures;QNetworkAccessManager* m_manager;
};#endif
#pragma execution_character_set("utf-8")
#include <QDir>
#include <QFile>
#include <QProcess>
#include <QMessageBox>
#include <QNetworkReply>
#include <QDesktopServices>
#include <QNetworkAccessManager>#include <math.h>#include "Downloader.h"static const QString PARTIAL_DOWN (".part");Downloader::Downloader (QWidget* parent) : QWidget (parent)
{m_ui = new Ui::Downloader;m_ui->setupUi (this);/* Initialize private members */m_manager = new QNetworkAccessManager();/* Initialize internal values */m_url = "";m_fileName = "";m_startTime = 0;m_useCustomProcedures = false;/* Set download directory */m_downloadDir = QDir::homePath() + "/Downloads/";/* Configure the appearance and behavior of the buttons */m_ui->openButton->setEnabled (false);m_ui->openButton->setVisible (false);connect (m_ui->stopButton, SIGNAL (clicked()),this,               SLOT (cancelDownload()));connect (m_ui->openButton, SIGNAL (clicked()),this,               SLOT (installUpdate()));/* Resize to fit */
}Downloader::~Downloader()
{delete m_ui;delete m_reply;delete m_manager;
}/*** Returns \c true if the updater shall not intervene when the download has* finished (you can use the \c QSimpleUpdater signals to know when the* download is completed).*/
bool Downloader::useCustomInstallProcedures() const
{return m_useCustomProcedures;
}/*** Changes the URL, which is used to indentify the downloader dialog* with an \c Updater instance** \note the \a url parameter is not the download URL, it is the URL of*       the AppCast file*/
void Downloader::setUrlId (const QString& url)
{m_url = url;
}/*** Begins downloading the file at the given \a url*/
void Downloader::startDownload (const QUrl& url)
{/* Reset UI */m_ui->progressBar->setValue (0);m_ui->stopButton->setText (tr ("Stop"));m_ui->downloadLabel->setText (tr ("Downloading updates"));m_ui->timeLabel->setText (tr ("Time remaining") + ": " + tr ("unknown"));/* Configure the network request */QNetworkRequest request (url);if (!m_userAgentString.isEmpty())request.setRawHeader ("User-Agent", m_userAgentString.toUtf8());/* Start download */m_reply = m_manager->get (request);m_startTime = QDateTime::currentDateTime().toTime_t();/* Ensure that downloads directory exists */if (!m_downloadDir.exists())m_downloadDir.mkpath (".");/* Remove old downloads */QFile::remove (m_downloadDir.filePath (m_fileName));QFile::remove (m_downloadDir.filePath (m_fileName + PARTIAL_DOWN));/* Update UI when download progress changes or download finishes */connect (m_reply, SIGNAL (downloadProgress (qint64, qint64)),this,      SLOT (updateProgress   (qint64, qint64)));connect (m_reply, SIGNAL (finished ()),this,      SLOT (finished ()));connect (m_reply, SIGNAL (redirected       (QUrl)),this,      SLOT (startDownload    (QUrl)));}/*** Changes the name of the downloaded file*/
void Downloader::setFileName (const QString& file)
{m_fileName = file;if (m_fileName.isEmpty())m_fileName = "QSU_Update.bin";
}/*** Changes the user-agent string used to communicate with the remote HTTP server*/
void Downloader::setUserAgentString (const QString& agent)
{m_userAgentString = agent;
}void Downloader::finished()
{/* Rename file */QFile::rename (m_downloadDir.filePath (m_fileName + PARTIAL_DOWN),m_downloadDir.filePath (m_fileName));/* Notify application */emit downloadFinished (m_url, m_downloadDir.filePath (m_fileName));/* Install the update */m_reply->close();installUpdate();setVisible (false);
}/*** Opens the downloaded file.* \note If the downloaded file is not found, then the function will alert the*       user about the error.*/
void Downloader::openDownload()
{if (!m_fileName.isEmpty())QDesktopServices::openUrl (QUrl::fromLocalFile (m_downloadDir.filePath (m_fileName)));else {QMessageBox::critical (this,tr ("Error"),tr ("Cannot find downloaded update!"),QMessageBox::Close);}
}/*** Instructs the OS to open the downloaded file.** \note If \c useCustomInstallProcedures() returns \c true, the function will*       not instruct the OS to open the downloaded file. You can use the*       signals fired by the \c QSimpleUpdater to install the update with your*       own implementations/code.*/
void Downloader::installUpdate()
{if (useCustomInstallProcedures())return;/* Update labels */m_ui->stopButton->setText    (tr ("Close"));m_ui->downloadLabel->setText (tr ("Download complete!"));m_ui->timeLabel->setText     (tr ("The installer will open separately")+ "...");/* Ask the user to install the download */QMessageBox box;box.setIcon (QMessageBox::Question);box.setDefaultButton   (QMessageBox::Ok);box.setStandardButtons (QMessageBox::Ok | QMessageBox::Cancel);box.setInformativeText (tr ("Click \"OK\" to begin installing the update"));box.setText ("<h3>" +tr ("In order to install the update, you may need to ""quit the application.")+ "</h3>");/* User wants to install the download */if (box.exec() == QMessageBox::Ok) {if (!useCustomInstallProcedures())openDownload();}/* Wait */else {m_ui->openButton->setEnabled (true);m_ui->openButton->setVisible (true);m_ui->timeLabel->setText (tr ("Click the \"Open\" button to ""apply the update"));}
}/*** Prompts the user if he/she wants to cancel the download and cancels the* download if the user agrees to do that.*/
void Downloader::cancelDownload()
{if (!m_reply->isFinished()) {QMessageBox box;box.setWindowTitle (tr ("Updater"));box.setIcon (QMessageBox::Question);box.setStandardButtons (QMessageBox::Yes | QMessageBox::No);box.setText (tr ("Are you sure you want to cancel the download?"));if (box.exec() == QMessageBox::Yes) {m_reply->abort();}}
}/*** Writes the downloaded data to the disk*/
void Downloader::saveFile (qint64 received, qint64 total)
{Q_UNUSED(received);Q_UNUSED(total);/* Check if we need to redirect */QUrl url = m_reply->attribute (QNetworkRequest::RedirectionTargetAttribute).toUrl();if (!url.isEmpty()) {startDownload (url);return;}/* Save downloaded data to disk */QFile file (m_downloadDir.filePath (m_fileName + PARTIAL_DOWN));if (file.open (QIODevice::WriteOnly | QIODevice::Append)) {file.write (m_reply->readAll());file.close();}
}/*** Calculates the appropiate size units (bytes, KB or MB) for the received* data and the total download size. Then, this function proceeds to update the* dialog controls/UI.*/
void Downloader::calculateSizes (qint64 received, qint64 total)
{QString totalSize;QString receivedSize;if (total < 1024)totalSize = tr ("%1 bytes").arg (total);else if (total < 1048576)totalSize = tr ("%1 KB").arg (round (total / 1024));elsetotalSize = tr ("%1 MB").arg (round (total / 1048576));if (received < 1024)receivedSize = tr ("%1 bytes").arg (received);else if (received < 1048576)receivedSize = tr ("%1 KB").arg (received / 1024);elsereceivedSize = tr ("%1 MB").arg (received / 1048576);m_ui->downloadLabel->setText (tr ("Downloading updates")+ " (" + receivedSize + " " + tr ("of")+ " " + totalSize + ")");
}/*** Uses the \a received and \a total parameters to get the download progress* and update the progressbar value on the dialog.*/
void Downloader::updateProgress (qint64 received, qint64 total)
{if (total > 0) {m_ui->progressBar->setMinimum (0);m_ui->progressBar->setMaximum (100);m_ui->progressBar->setValue ((received * 100) / total);calculateSizes (received, total);calculateTimeRemaining (received, total);saveFile (received, total);}else {m_ui->progressBar->setMinimum (0);m_ui->progressBar->setMaximum (0);m_ui->progressBar->setValue (-1);m_ui->downloadLabel->setText (tr ("Downloading Updates") + "...");m_ui->timeLabel->setText (QString ("%1: %2").arg (tr ("Time Remaining")).arg (tr ("Unknown")));}
}/*** Uses two time samples (from the current time and a previous sample) to* calculate how many bytes have been downloaded.** Then, this function proceeds to calculate the appropiate units of time* (hours, minutes or seconds) and constructs a user-friendly string, which* is displayed in the dialog.*/
void Downloader::calculateTimeRemaining (qint64 received, qint64 total)
{uint difference = QDateTime::currentDateTime().toTime_t() - m_startTime;if (difference > 0) {QString timeString;qreal timeRemaining = total / (received / difference);if (timeRemaining > 7200) {timeRemaining /= 3600;int hours = int (timeRemaining + 0.5);if (hours > 1)timeString = tr ("about %1 hours").arg (hours);elsetimeString = tr ("about one hour");}else if (timeRemaining > 60) {timeRemaining /= 60;int minutes = int (timeRemaining + 0.5);if (minutes > 1)timeString = tr ("%1 minutes").arg (minutes);elsetimeString = tr ("1 minute");}else if (timeRemaining <= 60) {int seconds = int (timeRemaining + 0.5);if (seconds > 1)timeString = tr ("%1 seconds").arg (seconds);elsetimeString = tr ("1 second");}m_ui->timeLabel->setText (tr ("Time remaining") + ": " + timeString);}
}/*** Rounds the given \a input to two decimal places*/
qreal Downloader::round (const qreal& input)
{return roundf (input * 100) / 100;
}QString Downloader::downloadDir() const
{return m_downloadDir.absolutePath();
}void Downloader::setDownloadDir(const QString& downloadDir)
{if(m_downloadDir.absolutePath() != downloadDir) {m_downloadDir = downloadDir;}
}/*** If the \a custom parameter is set to \c true, then the \c Downloader will not* attempt to open the downloaded file.** Use the signals fired by the \c QSimpleUpdater to implement your own install* procedures.*/
void Downloader::setUseCustomInstallProcedures (const bool custom)
{m_useCustomProcedures = custom;
}

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