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，包罗使用 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置惩罚网络哀求。
发送 GET 哀求：使用 QNetworkAccessManager 的 get 方法来发送一个GET哀求到指定的URL。
接收数据：通过重写槽函数 readyRead 来接收数据。
生存文件：将接收到的数据写入到文件中。
处置惩罚完成：当下载完成后，重写 finished 槽函数来处置惩罚完成的逻辑。
https://i-blog.csdnimg.cn/direct/1e9b6a4f1769495cb018ea04416cee5b.gif
#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_OBJECT
signals:
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));
else
totalSize = 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);
else
receivedSize = 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);
else
timeString = 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);
else
timeString = tr ("1 minute");
}
else if (timeRemaining <= 60) {
int seconds = int (timeRemaining + 0.5);
if (seconds > 1)
timeString = tr ("%1 seconds").arg (seconds);
else
timeString = 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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