废话不多说，先上图看效果：

http://s13/mw690/003vzqvzzy7mukYK7q4bc&690

部分代码展示：

Widget::Widget(QWidget *parent) :

    QWidget(parent),

    ui(new Ui::Widget)

{

    ui->setupUi(this);

    file = new QFile(this);

    ftp = new QFtp(this);

    // 当每条命令开始执行时发出相应的信号

    connect(ftp,SIGNAL(commandStarted(int)),this,SLOT(ftpCommandStarted(int)));

    // 当每条命令执行结束时发出相应的信号

    connect(ftp,SIGNAL(commandFinished(int,bool)),SLOT(ftpCommandFinished(int,bool)));

    ui->progressBar->setValue(0);

    //鼠标双击列表中的目录时，我们进入该目录

    connect(ui->fileList,SIGNAL(itemActivated(QTreeWidgetItem*,int)),this,SLOT(processItem(QTreeWidgetItem*,int)));

}

Widget::~Widget()

{

    delete ui;

}

void Widget::processItem(QTreeWidgetItem* item,int)  //双击打开一个目录

{

    QString name = item->text(0);

    if (isDirectory.value(name)) {  //如果这个文件是个目录，则打开

        ui->fileList->clear();

        isDirectory.clear();

        currentPath += '/';

        currentPath += name;

        ftp->cd(name);

        ftp->list();

        ui->cdToParentButton->setEnabled(true);

    }

}

void Widget::ftpCommandStarted(int)

{

    if(ftp->currentCommand() == QFtp::ConnectToHost){

        ui->label->setText(tr("正在连接到服务器..."));

    }

    if (ftp->currentCommand() == QFtp::Login){

        ui->label->setText(tr("正在登录..."));

    }

    if (ftp->currentCommand() == QFtp::Get){

        ui->label->setText(tr("正在下载..."));

    }

    else if (ftp->currentCommand() == QFtp::Close){

        ui->label->setText(tr("正在关闭连接..."));

    }

}

void Widget::ftpCommandFinished(int, bool error)

{

    if(ftp->currentCommand() == QFtp::ConnectToHost){

        if(error)

            ui->label->setText(tr("连接服务器出现错误：%1")

                               .arg(ftp->errorString()));

        else ui->label->setText(tr("连接到服务器成功"));

    }

    if (ftp->currentCommand() == QFtp::Login){

        if(error)

            ui->label->setText(tr("登录出现错误：%1")

                               .arg(ftp->errorString()));

        else

        {

            ui->label->setText(tr("登录成功"));

            ftp->list();   //发射listInfo()信号，显示文件列表

        }

    }

    if (ftp->currentCommand() == QFtp::Get){

        if(error)

            ui->label->setText(tr("下载出现错误：%1")

                               .arg(ftp->errorString()));

        else {

            ui->label->setText(tr("已经完成下载"));

            ui->downloaon->setEnabled(true);

            file->close();

            delete file;

        }

    }

    else if (ftp->currentCommand() == QFtp::Close){

        ui->label->setText(tr("已经关闭连接"));

    }

    if (ftp->currentCommand() == QFtp::List){

        if (isDirectory.isEmpty())

        { //如果目录为空,显示“empty”

            ui->fileList->addTopLevelItem(

                        new QTreeWidgetItem(QStringList()<< tr("")));

            ui->fileList->setEnabled(false);

            ui->label->setText(tr("该目录为空"));

        }

    }

}

void Widget::on_connectButton_clicked()

{

    ui->fileList->clear();

    currentPath.clear();

    isDirectory.clear();

    ftp = new QFtp(this);

    connect(ftp,SIGNAL(commandStarted(int)),this,SLOT(ftpCommandStarted(int)));

    connect(ftp,SIGNAL(commandFinished(int,bool)),this,SLOT(ftpCommandFinished(int,bool)));

    connect(ftp,SIGNAL(listInfo(QUrlInfo)),this,SLOT(addToList(QUrlInfo)));

    connect(ftp,SIGNAL(dataTransferProgress(qint64,qint64)),this,SLOT(updateDataTransferProgress(qint64,qint64)));

    QString ftpServer = ui->ftpServerLineEdit->text();

    QString userName = ui->userNameLineEdit->text();

    QString passWord = ui->passWordLineEdit->text();

    ftp->connectToHost(ftpServer,21); //连接到服务器,默认端口号是21

    ftp->login(userName,passWord);   //登录

}

void Widget::updateDataTransferProgress(qint64 readBytes,qint64 totalBytes)

{

    ui->progressBar->setMaximum(totalBytes);

    ui->progressBar->setValue(readBytes);

}

void Widget::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() ? "../ftpclient2/dir.png" : "../ftpclient2/file.png");

    item->setIcon(0, pixmap);

    isDirectory[urlInfo.name()] = urlInfo.isDir();

    //存储该路径是否为目录的信息

    ui->fileList->addTopLevelItem(item);

    if (!ui->fileList->currentItem()) {

        ui->fileList->setCurrentItem(ui->fileList->topLevelItem(0));

        ui->fileList->setEnabled(true);

    }

}

void Widget::on_cdToParentButton_clicked()

{

    ui->fileList->clear();

    isDirectory.clear();

    currentPath = currentPath.left(currentPath.lastIndexOf('/'));

    if (currentPath.isEmpty()) {

        ui->cdToParentButton->setEnabled(false);

        ftp->cd("/");

    } else {

        ftp->cd(currentPath);

    }

    ftp->list();

}

void Widget::on_downloaon_clicked()

{

    QString fileName = ui->fileList->currentItem()->text(0);

    file = new QFile(fileName);

    if (!file->open(QIODevice::WriteOnly))

    {

        delete file;

        return;

    }

    //下载按钮不可用，等下载完成后才可用

    ui->downloaon->setEnabled(false);

    ftp->get(ui->fileList->currentItem()->text(0), file);

}

仁至义尽啊！！！

新手在此感谢yafeilinux开源社区！！！