Implementing filedownloader to QML

[PsAePr]

Hi,

for my software, i need to download a file to my local HDD. I found this example:
"Downloading file from URL":http://qt-project.org/forums/viewthread/16749
and tried to use it. The result looks like this:

main.cpp
@
//main.cpp
#include <QtGui/QGuiApplication>
#include "qtquick2applicationviewer.h"
#include "filedownloader.h"
#include <QQmlEngine>
#include <QtQml>
#include <QtDebug>
#include <QObject>

FileDownloader* n;
QNetworkAccessManager* nam;
QObject* parent;

int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv);
QtQuick2ApplicationViewer viewer;
QUrl imageURL("http://i.imgur.com/Uw7Fk.jpg");
viewer.setMainQmlFile(QStringLiteral("qml/DownloadTest4/main.qml"));
viewer.showExpanded();
n = new FileDownloader(imageURL, parent);
//app.connect(n, SIGNAL(downloaded()),SLOT);
return app.exec();
}@

filedownloader.cpp
@
//filedownloader.cpp
#include "filedownloader.h"
#include <QDebug>
#include <QFile>

FileDownloader::FileDownloader(QUrl imageUrl, QObject parent) :
QObject(parent)
{
connect(&m_WebCtrl, SIGNAL(finished(QNetworkReply)),
SLOT(fileDownloaded(QNetworkReply*)));

QNetworkRequest request(imageUrl);
m_WebCtrl.get(request);
qDebug()<<"Request sent!";

}

FileDownloader::~FileDownloader()
{

}

void FileDownloader::fileDownloaded(QNetworkReply* pReply)
{
qDebug()<<"Download successful!";
m_DownloadedData = pReply->readAll();
QFile file("D:\Test.jpg");
file.open(QIODevice::WriteOnly);
file.write(pReply->readAll());
//emit a signal
pReply->deleteLater();
emit downloaded();

}

QByteArray FileDownloader::downloadedData() const
{
return m_DownloadedData;
}@

filedownloader.h
@
//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@

Now i have the problem that i get my two console logs "Request sent!" and "Download successful!" but i can't find the file that should have been created.
Am i doing anything wrong with QFile?

My second problem is the including of "filedownloader.h" into a QML-file.

I know that I have to register the C++ as a type, like this:
@qmlRegisterType<filedownloader>("my.library", 1, 0, "FileDownloader");@
but it's not working.

I hope somebody can help me :)

[stevenceuppens]

Hi,

in your example code you do:

@void FileDownloader::fileDownloaded(QNetworkReply* pReply)
{
qDebug()<<"Download successful!";
m_DownloadedData = pReply->readAll();
QFile file("D:\Test.jpg");
file.open(QIODevice::WriteOnly);
file.write(pReply->readAll());
//emit a signal
pReply->deleteLater();
emit downloaded();
}
@

the line "m_DownloadedData = pReply->readAll();" creates this issue,

after this line, the buffer of your network reply is empty, and the data is inside "m_DownloadedData"

a few lines lower, you try to save the image by doing: "file.write(pReply->readAll());"

but the buffer is already empty...

so you shoud do: "file.write( m_DownloadedData );"

i should do,

@
void FileDownloader::fileDownloaded(QNetworkReply* pReply)
{
qDebug()<<"Download successful!";
QFile file("D:\Test.jpg");

if( !file.open(QIODevice::WriteOnly) )
    return;  // file could not be created

file.write(pReply->readAll());
//emit a signal
pReply->deleteLater();
emit downloaded();

}
@

and remove the variable "m_DownloadedData"

for your second issue,

you also have to include the macro QML_DECLARE_TYPE(CLASSNAME)
in your header file, before you can use the qmlRegisterType method.

so:

@
//filedownloader.h
#ifndef FILEDOWNLOADER_H
#define FILEDOWNLOADER_H

#include <QtQml> // add for QML_DECLARE_TYPE macro !!!!!

#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;

};

QML_DECLARE_TYPE( FileDownloader ) // marco !!

#endif // FILEDOWNLOADER_H
@