Qt 5.9 | Qt Network | Network Download Manager Example | downloadmanager.cpp Example File

Qt 5.9.9 Reference Documentation

# downloadmanager.cpp Example File

downloadmanager/downloadmanager.cpp

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      #include "downloadmanager.h"

      #include <QFileInfo>
      #include <QNetworkRequest>
      #include <QNetworkReply>
      #include <QString>
      #include <QStringList>
      #include <QTimer>
      #include <stdio.h>

      DownloadManager::DownloadManager(QObject *parent)
          : QObject(parent), downloadedCount(0), totalCount(0)
      {
      }

      void DownloadManager::append(const QStringList &urlList)
      {
          foreach (QString url, urlList)
              append(QUrl::fromEncoded(url.toLocal8Bit()));

          if (downloadQueue.isEmpty())
              QTimer::singleShot(0, this, SIGNAL(finished()));
      }

      void DownloadManager::append(const QUrl &url)
      {
          if (downloadQueue.isEmpty())
              QTimer::singleShot(0, this, SLOT(startNextDownload()));

          downloadQueue.enqueue(url);
          ++totalCount;
      }

      QString DownloadManager::saveFileName(const QUrl &url)
      {
          QString path = url.path();
          QString basename = QFileInfo(path).fileName();

          if (basename.isEmpty())
              basename = "download";

          if (QFile::exists(basename)) {
              // already exists, don't overwrite
              int i = 0;
              basename += '.';
              while (QFile::exists(basename + QString::number(i)))
                  ++i;

              basename += QString::number(i);
          }

          return basename;
      }

      void DownloadManager::startNextDownload()
      {
          if (downloadQueue.isEmpty()) {
              printf("%d/%d files downloaded successfully\n", downloadedCount, totalCount);
              emit finished();
              return;
          }

          QUrl url = downloadQueue.dequeue();

          QString filename = saveFileName(url);
          output.setFileName(filename);
          if (!output.open(QIODevice::WriteOnly)) {
              fprintf(stderr, "Problem opening save file '%s' for download '%s': %s\n",
                      qPrintable(filename), url.toEncoded().constData(),
                      qPrintable(output.errorString()));

              startNextDownload();
              return;                 // skip this download
          }

          QNetworkRequest request(url);
          currentDownload = manager.get(request);
          connect(currentDownload, SIGNAL(downloadProgress(qint64,qint64)),
                  SLOT(downloadProgress(qint64,qint64)));
          connect(currentDownload, SIGNAL(finished()),
                  SLOT(downloadFinished()));
          connect(currentDownload, SIGNAL(readyRead()),
                  SLOT(downloadReadyRead()));

          // prepare the output
          printf("Downloading %s...\n", url.toEncoded().constData());
          downloadTime.start();
      }

      void DownloadManager::downloadProgress(qint64 bytesReceived, qint64 bytesTotal)
      {
          progressBar.setStatus(bytesReceived, bytesTotal);

          // calculate the download speed
          double speed = bytesReceived * 1000.0 / downloadTime.elapsed();
          QString unit;
          if (speed < 1024) {
              unit = "bytes/sec";
          } else if (speed < 1024*1024) {
              speed /= 1024;
              unit = "kB/s";
          } else {
              speed /= 1024*1024;
              unit = "MB/s";
          }

          progressBar.setMessage(QString::fromLatin1("%1 %2")
                                 .arg(speed, 3, 'f', 1).arg(unit));
          progressBar.update();
      }

      void DownloadManager::downloadFinished()
      {
          progressBar.clear();
          output.close();

          if (currentDownload->error()) {
              // download failed
              fprintf(stderr, "Failed: %s\n", qPrintable(currentDownload->errorString()));
          } else {
              printf("Succeeded.\n");
              ++downloadedCount;
          }

          currentDownload->deleteLater();
          startNextDownload();
      }

      void DownloadManager::downloadReadyRead()
      {
          output.write(currentDownload->readAll());
      }