Download Data from URL: Difference between revisions
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{{LangSwitch}} | |||
[[Category:HowTo]] | [[Category:HowTo]] | ||
== Introduction == | |||
The following code snippet demonstrates how to download data as {{DocLink|QByteArray}} from URL. The downloaded data can be saved as a file or converted to appropriate object. For example if an image is downloaded it can be converted to {{DocLink|QPixmap}} or {{DocLink|QImage}} using method {{DocLink|QImage|loadFromData}}. | |||
Please note that although the name of the class is File''Downloader'' the downloaded data is not saved on the disk as file! | |||
Please note that although the name of the class is | |||
== Important Classes == | == Important Classes == | ||
Line 24: | Line 17: | ||
<code> | <code> | ||
QT | QT += network | ||
</code> | </code> | ||
Line 48: | Line 35: | ||
{ | { | ||
Q_OBJECT | Q_OBJECT | ||
public: | public: | ||
explicit FileDownloader(QUrl imageUrl, QObject *parent = 0); | |||
virtual ~FileDownloader(); | |||
QByteArray downloadedData() const; | |||
void | signals: | ||
void downloaded(); | |||
private: | private slots: | ||
void fileDownloaded(QNetworkReply* pReply); | |||
private: | |||
QNetworkAccessManager m_WebCtrl; | |||
QByteArray m_DownloadedData; | |||
}; | }; | ||
Line 78: | Line 59: | ||
#include "filedownloader.h" | #include "filedownloader.h" | ||
FileDownloader::FileDownloader(QUrl imageUrl, QObject | FileDownloader::FileDownloader(QUrl imageUrl, QObject *parent) : | ||
QObject(parent) | QObject(parent) | ||
{ | { | ||
connect(& | connect( | ||
&m_WebCtrl, SIGNAL (finished(QNetworkReply*)), | |||
this, SLOT (fileDownloaded(QNetworkReply*)) | |||
); | |||
QNetworkRequest request(imageUrl); | QNetworkRequest request(imageUrl); | ||
Line 88: | Line 71: | ||
} | } | ||
FileDownloader::~FileDownloader() | FileDownloader::~FileDownloader() { } | ||
{ | |||
} | |||
void FileDownloader::fileDownloaded(QNetworkReply | void FileDownloader::fileDownloaded(QNetworkReply* pReply) { | ||
{ | |||
m_DownloadedData = pReply->readAll(); | m_DownloadedData = pReply->readAll(); | ||
//emit a signal | //emit a signal | ||
Line 101: | Line 80: | ||
} | } | ||
QByteArray FileDownloader::downloadedData() const | QByteArray FileDownloader::downloadedData() const { | ||
{ | |||
return m_DownloadedData; | return m_DownloadedData; | ||
} | } | ||
</code> | </code> | ||
= Usage = | == Usage == | ||
== Load Pixmap from URL == | === Load Pixmap from URL === | ||
Declare slot | |||
<code> | <code> | ||
private slots: | private slots: | ||
void loadImage(); | |||
void loadImage(); | |||
</code> | </code> | ||
Connect signal '''downloaded()''' to the slot | |||
<code> | <code> | ||
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m_pImgCtrl = new FileDownloader(imageUrl, this); | m_pImgCtrl = new FileDownloader(imageUrl, this); | ||
connect(m_pImgCtrl, SIGNAL (downloaded()), SLOT (loadImage())); | connect(m_pImgCtrl, SIGNAL (downloaded()), this, SLOT (loadImage())); | ||
</code> | </code> | ||
Load QPixmap from the downloaded data | |||
<code> | <code> |
Revision as of 09:29, 23 October 2015
Introduction
The following code snippet demonstrates how to download data as QByteArray from URL. The downloaded data can be saved as a file or converted to appropriate object. For example if an image is downloaded it can be converted to QPixmap or QImage using method loadFromData.
Please note that although the name of the class is FileDownloader the downloaded data is not saved on the disk as file!
Important Classes
.pro File
QT += network
filedownloader.h
#ifndef FILEDOWNLOADER_H
#define FILEDOWNLOADER_H
#include <QObject>
#include <QByteArray>
#include <QNetworkAccessManager>
#include <QNetworkRequest>
#include <QNetworkReply>
class FileDownloader : public QObject
{
Q_OBJECT
public:
explicit FileDownloader(QUrl imageUrl, QObject *parent = 0);
virtual ~FileDownloader();
QByteArray downloadedData() const;
signals:
void downloaded();
private slots:
void fileDownloaded(QNetworkReply* pReply);
private:
QNetworkAccessManager m_WebCtrl;
QByteArray m_DownloadedData;
};
#endif // FILEDOWNLOADER_H
filedownloader.cpp
#include "filedownloader.h"
FileDownloader::FileDownloader(QUrl imageUrl, QObject *parent) :
QObject(parent)
{
connect(
&m_WebCtrl, SIGNAL (finished(QNetworkReply*)),
this, SLOT (fileDownloaded(QNetworkReply*))
);
QNetworkRequest request(imageUrl);
m_WebCtrl.get(request);
}
FileDownloader::~FileDownloader() { }
void FileDownloader::fileDownloaded(QNetworkReply* pReply) {
m_DownloadedData = pReply->readAll();
//emit a signal
pReply->deleteLater();
emit downloaded();
}
QByteArray FileDownloader::downloadedData() const {
return m_DownloadedData;
}
Usage
Load Pixmap from URL
Declare slot
private slots:
void loadImage();
Connect signal downloaded() to the slot
QUrl imageUrl("http://qt.digia.com/Documents/1/QtLogo.png");
m_pImgCtrl = new FileDownloader(imageUrl, this);
connect(m_pImgCtrl, SIGNAL (downloaded()), this, SLOT (loadImage()));
Load QPixmap from the downloaded data
void MainWindow::loadImage()
{
QPixmap buttonImage;
buttonImage.loadFromData(m_pImgCtrl->downloadedData());
}