Adding code example to QT C++

Question

I'd like to add some QT example code to my simple project. The sample code is here: https://wiki.qt.io/Download_Data_from_URL

It consists of filedownloader.cpp and filedownloader.h -- this code downloads a graphic from a supplied URL.

I've added these files to my project and get a clean compile. I think I understand the code ok (I'm mainly a c coder, not c++) but I don't understand how I can pass the QUrl created by my project to filedownloader.cpp

The "project" is just a simple main.cpp/mainwindow.cpp/mainwindow.ui that offers a button to be pressed. Pressing the button calls the routine below:

void MainWindow::on_pushButton_clicked()
{
// pass to filedownloader to process
QUrl fileloc("http://www.test.com/test.jpg");
}

How do I feed the QUrl fileloc to filedownload.cpp?

Alexander Shishenko · Accepted Answer · 2016-01-16 02:55:10Z

1

You have to add a new method to FileDownloader, that accepts QUrl and starts the download.

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();

 public slots:
  void download(QUrl url);   // <------ Here it is

 private slots:
  void fileDownloaded(QNetworkReply* pReply);

 private:
  QNetworkAccessManager m_WebCtrl;
  QByteArray m_DownloadedData;
};

#endif // FILEDOWNLOADER_H

filedownloader.cpp:

#include "filedownloader.h"

FileDownloader::FileDownloader(QObject *parent) :
 QObject(parent)
{
 connect(
  &m_WebCtrl, SIGNAL (finished(QNetworkReply*)),
  this, SLOT (fileDownloaded(QNetworkReply*))
  );
 // <------ Notice, that i've removed downloading code from here
}

FileDownloader::~FileDownloader() { }

void FileDownloader::fileDownloaded(QNetworkReply* pReply) {
 m_DownloadedData = pReply->readAll();
 //emit a signal
 pReply->deleteLater();
 emit downloaded();
}

void FileDownloader::download(QUrl url) { // <------ And its definition
 QNetworkRequest request(url);
 m_WebCtrl.get(request);
}

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

And then your on_pushButton_clicked will look like this:

void MainWindow::on_pushButton_clicked()
{
// pass to filedownloader to process
QUrl fileloc("http://www.test.com/test.jpg");
m_filedownloader.download(fileloc);
}

answered Jan 16, 2016 at 2:55

Alexander Shishenko

9601 gold badge11 silver badges28 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Frank Osterfeld Over a year ago

The idea of the class seems rather to create one FileDownloader object per download and pass the url as ctor argument. I don’t see any need for your modification. It just adds complexity. E.g., if download() is called twice, it’s impossible to find out which download() call downloaded() refers to and one download replaces the other.

Collectives™ on Stack Overflow

Adding code example to QT C++

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related