7.11 实例：编写ftp客户端程序.txt

qt的源代码

private slots:
     void connectOrDisconnect();
     void downloadFile();
     void cancelDownload();
     void ftpCommandFinished(int commandId, bool error);
     void addToList(const QUrlInfo &urlInfo);
     void processItem(QTreeWidgetItem *item, int column);
     void cdToParent();
     void updateDataTransferProgress(qint64 readBytes,
                                     qint64 totalBytes);
     void enableDownloadButton();
 QHash<QString, bool> isDirectory;
     QString currentPath;
     QFtp *ftp;
     QFile *file;
 void FtpWindow::connectOrDisconnect()
 {
     if (ftp) {
         ftp->abort();
         ftp->deleteLater();
         ftp = 0;
  ...
     ftp = new QFtp(this);
     connect(ftp, SIGNAL(commandFinished(int, bool)),
             this, SLOT(ftpCommandFinished(int, bool)));
     connect(ftp, SIGNAL(listInfo(const QUrlInfo &)),
             this, SLOT(addToList(const QUrlInfo &)));
     connect(ftp, SIGNAL(dataTransferProgress(qint64, qint64)),
             this, SLOT(updateDataTransferProgress(qint64, qint64)));
     fileList->clear();
     currentPath.clear();
     isDirectory.clear();
 QUrl url(ftpServerLineEdit->text());
     if (!url.isValid() || url.scheme().toLower() != QLatin1String("ftp")) {
         ftp->connectToHost(ftpServerLineEdit->text(), 21);
         ftp->login();
     } else {
         ftp->connectToHost(url.host(), url.port(21));
         if (!url.userName().isEmpty())
             ftp->login(QUrl::fromPercentEncoding(url.userName().toLatin1()), url.password());
         else
             ftp->login();
         if (!url.path().isEmpty())
             ftp->cd(url.path());
   }
void FtpWindow::downloadFile()
 {
     QString fileName = fileList->currentItem()->text(0);
     ...
     file = new QFile(fileName);
     if (!file->open(QIODevice::WriteOnly)) {
         QMessageBox::information(this, tr("FTP"),
                                  tr("Unable to save the file %1: %2.")
                                  .arg(fileName).arg(file->errorString()));
         delete file;
         return;
     }
     ftp->get(fileList->currentItem()->text(0), file);
     progressDialog->setLabelText(tr("Downloading %1...").arg(fileName));
     downloadButton->setEnabled(false);
     progressDialog->exec();
 }
 void FtpWindow::cancelDownload()
 {
     ftp->abort();
 }
void FtpWindow::ftpCommandFinished(int, bool error)
 {
 #ifndef QT_NO_CURSOR
     setCursor(Qt::ArrowCursor);
 #endif
     if (ftp->currentCommand() == QFtp::ConnectToHost) {
         if (error) {
             QMessageBox::information(this, tr("FTP"),
                                      tr("Unable to connect to the FTP server "
                                         "at %1. Please check that the host "
                                         "name is correct.")
                                      .arg(ftpServerLineEdit->text()));
             connectOrDisconnect();
             return;
     }
         statusLabel->setText(tr("Logged onto %1.")
                              .arg(ftpServerLineEdit->text()));
         fileList->setFocus();
         downloadButton->setDefault(true);
         connectButton->setEnabled(true);
         return;
     }
   if (ftp->currentCommand() == QFtp::Login)
         ftp->list();
  if (ftp->currentCommand() == QFtp::Get) {
         if (error) {
             statusLabel->setText(tr("Canceled download of %1.")
                                  .arg(file->fileName()));
             file->close();
             file->remove();
         } else {
             statusLabel->setText(tr("Downloaded %1 to current directory.")
                                  .arg(file->fileName()));
             file->close();
         }
         delete file;
         enableDownloadButton();
         progressDialog->hide();
/*当Get 命令结束后，说明文件已经完成下载，或者在下载的过程当中出现了错误*/
            } else if (ftp->currentCommand() == QFtp::List) {
         if (isDirectory.isEmpty()) {
             fileList->addTopLevelItem(new QTreeWidgetItem(QStringList() << tr("<empty>")));
             fileList->setEnabled(false);
         }
     }
  void FtpWindow::addToList(const QUrlInfo &urlInfo)
 {
     QTreeWidgetItem *item = new QTreeWidgetItem;
     item->setText(0, urlInfo.name());
     item->setText(1, QString::number(urlInfo.size()));
     item->setText(2, urlInfo.owner());
     item->setText(3, urlInfo.group());
     item->setText(4, urlInfo.lastModified().toString("MMM dd yyyy"));
     QPixmap pixmap(urlInfo.isDir() ? ":/images/dir.png" : ":/images/file.png");
     item->setIcon(0, pixmap);
     isDirectory[urlInfo.name()] = urlInfo.isDir();
     fileList->addTopLevelItem(item);
     if (!fileList->currentItem()) {
         fileList->setCurrentItem(fileList->topLevelItem(0));
         fileList->setEnabled(true);
     }
 }
 void FtpWindow::processItem(QTreeWidgetItem *item, int /*column*/)
 {
     QString name = item->text(0);
     if (isDirectory.value(name)) {
         fileList->clear();
         isDirectory.clear();
         currentPath += "/" + name;
         ftp->cd(name);
         ftp->list();
         cdToParentButton->setEnabled(true);
 #ifndef QT_NO_CURSOR
         setCursor(Qt::WaitCursor);
 #endif
         return;
     }
 }
 void FtpWindow::cdToParent()
 {
 #ifndef QT_NO_CURSOR
     setCursor(Qt::WaitCursor);
 #endif
     fileList->clear();
     isDirectory.clear();
     currentPath = currentPath.left(currentPath.lastIndexOf('/'));
     if (currentPath.isEmpty()) {
         cdToParentButton->setEnabled(false);
         ftp->cd("/");
     } else {
         ftp->cd(currentPath);
     }
   ftp->list();
 }
void FtpWindow::updateDataTransferProgress(qint64 readBytes,
                                            qint64 totalBytes)
 {
     progressDialog->setMaximum(totalBytes);
     progressDialog->setValue(readBytes);
 }
void FtpWindow::enableDownloadButton()
 {
     QTreeWidgetItem *current = fileList->currentItem();
     if (current) {
         QString currentFile = current->text(0);
         downloadButton->setEnabled(!isDirectory.value(currentFile));
     } else {
         downloadButton->setEnabled(false);
     }
 }