Qt 5.6 | Qt Network | HTTP Example | httpwindow.cpp Example File

Qt 5.6.3 Reference Documentation

# httpwindow.cpp Example File

http/httpwindow.cpp

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      ** Contact: http://www.qt.io/licensing/
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      ** This file is part of the examples of the Qt Toolkit.
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      #include <QtWidgets>
      #include <QtNetwork>
      #include <QUrl>

      #include "httpwindow.h"
      #include "ui_authenticationdialog.h"

      #ifndef QT_NO_SSL
      static const char defaultUrl[] = "https://www.qt.io/";
      #else
      static const char defaultUrl[] = "http://www.qt.io/";
      #endif
      static const char defaultFileName[] = "index.html";

      ProgressDialog::ProgressDialog(const QUrl &url, QWidget *parent)
        : QProgressDialog(parent)
      {
          setWindowTitle(tr("Download Progress"));
          setWindowFlags(windowFlags() & ~Qt::WindowContextHelpButtonHint);
          setLabelText(tr("Downloading %1.").arg(url.toDisplayString()));
          setMinimum(0);
          setValue(0);
          setMinimumDuration(0);
      }

      void ProgressDialog::networkReplyProgress(qint64 bytesRead, qint64 totalBytes)
      {
          setMaximum(totalBytes);
          setValue(bytesRead);
      }

      HttpWindow::HttpWindow(QWidget *parent)
          : QDialog(parent)
          , statusLabel(new QLabel(tr("Please enter the URL of a file you want to download.\n\n"), this))
          , urlLineEdit(new QLineEdit(defaultUrl))
          , downloadButton(new QPushButton(tr("Download")))
          , launchCheckBox(new QCheckBox("Launch file"))
          , defaultFileLineEdit(new QLineEdit(defaultFileName))
          , downloadDirectoryLineEdit(new QLineEdit)
          , reply(Q_NULLPTR)
          , file(Q_NULLPTR)
          , httpRequestAborted(false)
      {
          setWindowFlags(windowFlags() & ~Qt::WindowContextHelpButtonHint);
          setWindowTitle(tr("HTTP"));

          connect(&qnam, &QNetworkAccessManager::authenticationRequired,
                  this, &HttpWindow::slotAuthenticationRequired);
      #ifndef QT_NO_SSL
          connect(&qnam, &QNetworkAccessManager::sslErrors,
                  this, &HttpWindow::sslErrors);
      #endif

          QFormLayout *formLayout = new QFormLayout;
          urlLineEdit->setClearButtonEnabled(true);
          connect(urlLineEdit, &QLineEdit::textChanged,
                  this, &HttpWindow::enableDownloadButton);
          formLayout->addRow(tr("&URL:"), urlLineEdit);
          QString downloadDirectory = QStandardPaths::writableLocation(QStandardPaths::TempLocation);
          if (downloadDirectory.isEmpty() || !QFileInfo(downloadDirectory).isDir())
              downloadDirectory = QDir::currentPath();
          downloadDirectoryLineEdit->setText(QDir::toNativeSeparators(downloadDirectory));
          formLayout->addRow(tr("&Download directory:"), downloadDirectoryLineEdit);
          formLayout->addRow(tr("Default &file:"), defaultFileLineEdit);
          launchCheckBox->setChecked(true);
          formLayout->addRow(launchCheckBox);

          QVBoxLayout *mainLayout = new QVBoxLayout(this);
          mainLayout->addLayout(formLayout);

          mainLayout->addItem(new QSpacerItem(0, 0, QSizePolicy::Ignored, QSizePolicy::MinimumExpanding));

          statusLabel->setWordWrap(true);
          mainLayout->addWidget(statusLabel);

          downloadButton->setDefault(true);
          connect(downloadButton, &QAbstractButton::clicked, this, &HttpWindow::downloadFile);
          QPushButton *quitButton = new QPushButton(tr("Quit"));
          quitButton->setAutoDefault(false);
          connect(quitButton, &QAbstractButton::clicked, this, &QWidget::close);
          QDialogButtonBox *buttonBox = new QDialogButtonBox;
          buttonBox->addButton(downloadButton, QDialogButtonBox::ActionRole);
          buttonBox->addButton(quitButton, QDialogButtonBox::RejectRole);
          mainLayout->addWidget(buttonBox);

          urlLineEdit->setFocus();
      }

      void HttpWindow::startRequest(const QUrl &requestedUrl)
      {
          url = requestedUrl;
          httpRequestAborted = false;

          reply = qnam.get(QNetworkRequest(url));
          connect(reply, &QNetworkReply::finished, this, &HttpWindow::httpFinished);
          connect(reply, &QIODevice::readyRead, this, &HttpWindow::httpReadyRead);

          ProgressDialog *progressDialog = new ProgressDialog(url, this);
          progressDialog->setAttribute(Qt::WA_DeleteOnClose);
          connect(progressDialog, &QProgressDialog::canceled, this, &HttpWindow::cancelDownload);
          connect(reply, &QNetworkReply::downloadProgress, progressDialog, &ProgressDialog::networkReplyProgress);
          connect(reply, &QNetworkReply::finished, progressDialog, &ProgressDialog::hide);
          progressDialog->show();

          statusLabel->setText(tr("Downloading %1...").arg(url.toString()));
      }

      void HttpWindow::downloadFile()
      {
          const QString urlSpec = urlLineEdit->text().trimmed();
          if (urlSpec.isEmpty())
              return;

          const QUrl newUrl = QUrl::fromUserInput(urlSpec);
          if (!newUrl.isValid()) {
              QMessageBox::information(this, tr("Error"),
                                       tr("Invalid URL: %1: %2").arg(urlSpec, newUrl.errorString()));
              return;
          }

          QString fileName = newUrl.fileName();
          if (fileName.isEmpty())
              fileName = defaultFileLineEdit->text().trimmed();
          if (fileName.isEmpty())
              fileName = defaultFileName;
          QString downloadDirectory = QDir::cleanPath(downloadDirectoryLineEdit->text().trimmed());
          if (!downloadDirectory.isEmpty() && QFileInfo(downloadDirectory).isDir())
              fileName.prepend(downloadDirectory + '/');
          if (QFile::exists(fileName)) {
              if (QMessageBox::question(this, tr("Overwrite Existing File"),
                                        tr("There already exists a file called %1 in "
                                           "the current directory. Overwrite?").arg(fileName),
                                        QMessageBox::Yes|QMessageBox::No, QMessageBox::No)
                  == QMessageBox::No)
                  return;
              QFile::remove(fileName);
          }

          file = openFileForWrite(fileName);
          if (!file)
              return;

          downloadButton->setEnabled(false);

          // schedule the request
          startRequest(newUrl);
      }

      QFile *HttpWindow::openFileForWrite(const QString &fileName)
      {
          QScopedPointer<QFile> file(new QFile(fileName));
          if (!file->open(QIODevice::WriteOnly)) {
              QMessageBox::information(this, tr("Error"),
                                       tr("Unable to save the file %1: %2.")
                                       .arg(QDir::toNativeSeparators(fileName),
                                            file->errorString()));
              return Q_NULLPTR;
          }
          return file.take();
      }

      void HttpWindow::cancelDownload()
      {
          statusLabel->setText(tr("Download canceled."));
          httpRequestAborted = true;
          reply->abort();
          downloadButton->setEnabled(true);
      }

      void HttpWindow::httpFinished()
      {
          QFileInfo fi;
          if (file) {
              fi.setFile(file->fileName());
              file->close();
              delete file;
              file = Q_NULLPTR;
          }

          if (httpRequestAborted) {
              reply->deleteLater();
              reply = Q_NULLPTR;
              return;
          }

          if (reply->error()) {
              QFile::remove(fi.absoluteFilePath());
              statusLabel->setText(tr("Download failed:\n%1.").arg(reply->errorString()));
              downloadButton->setEnabled(true);
              reply->deleteLater();
              reply = Q_NULLPTR;
              return;
          }

          const QVariant redirectionTarget = reply->attribute(QNetworkRequest::RedirectionTargetAttribute);

          reply->deleteLater();
          reply = Q_NULLPTR;

          if (!redirectionTarget.isNull()) {
              const QUrl redirectedUrl = url.resolved(redirectionTarget.toUrl());
              if (QMessageBox::question(this, tr("Redirect"),
                                        tr("Redirect to %1 ?").arg(redirectedUrl.toString()),
                                        QMessageBox::Yes | QMessageBox::No) == QMessageBox::No) {
                  downloadButton->setEnabled(true);
                  return;
              }
              file = openFileForWrite(fi.absoluteFilePath());
              if (!file) {
                  downloadButton->setEnabled(true);
                  return;
              }
              startRequest(redirectedUrl);
              return;
          }

          statusLabel->setText(tr("Downloaded %1 bytes to %2\nin\n%3")
                               .arg(fi.size()).arg(fi.fileName(), QDir::toNativeSeparators(fi.absolutePath())));
          if (launchCheckBox->isChecked())
              QDesktopServices::openUrl(QUrl::fromLocalFile(fi.absoluteFilePath()));
          downloadButton->setEnabled(true);
      }

      void HttpWindow::httpReadyRead()
      {
          // this slot gets called every time the QNetworkReply has new data.
          // We read all of its new data and write it into the file.
          // That way we use less RAM than when reading it at the finished()
          // signal of the QNetworkReply
          if (file)
              file->write(reply->readAll());
      }

      void HttpWindow::enableDownloadButton()
      {
          downloadButton->setEnabled(!urlLineEdit->text().isEmpty());
      }

      void HttpWindow::slotAuthenticationRequired(QNetworkReply*,QAuthenticator *authenticator)
      {
          QDialog authenticationDialog;
          Ui::Dialog ui;
          ui.setupUi(&authenticationDialog);
          authenticationDialog.adjustSize();
          ui.siteDescription->setText(tr("%1 at %2").arg(authenticator->realm(), url.host()));

          // Did the URL have information? Fill the UI
          // This is only relevant if the URL-supplied credentials were wrong
          ui.userEdit->setText(url.userName());
          ui.passwordEdit->setText(url.password());

          if (authenticationDialog.exec() == QDialog::Accepted) {
              authenticator->setUser(ui.userEdit->text());
              authenticator->setPassword(ui.passwordEdit->text());
          }
      }

      #ifndef QT_NO_SSL
      void HttpWindow::sslErrors(QNetworkReply*,const QList<QSslError> &errors)
      {
          QString errorString;
          foreach (const QSslError &error, errors) {
              if (!errorString.isEmpty())
                  errorString += '\n';
              errorString += error.errorString();
          }

          if (QMessageBox::warning(this, tr("SSL Errors"),
                                   tr("One or more SSL errors has occurred:\n%1").arg(errorString),
                                   QMessageBox::Ignore | QMessageBox::Abort) == QMessageBox::Ignore) {
              reply->ignoreSslErrors();
          }
      }
      #endif