qt文件http网络下载

参考 ：http://www.cppblog.com/gaimor/archive/2011/11/16/160289.html

#ifndef DOWMLOADWIDGET_H
#define DOWMLOADWIDGET_H

#include <QWidget>
#include <QProgressDialog>
#include <QUrl>
#include <QNetworkAccessManager>
#include <QNetworkReply>
#include <QFile>


namespace Ui {
class DowmloadWidget;
}

class DowmloadWidget : public QWidget
{
    Q_OBJECT

public:
    explicit DowmloadWidget(QWidget *parent = 0);
    ~DowmloadWidget();

    void startRequest(QUrl url);

private slots:
    void downloadFile();
    void cancelDownload();
    void httpFinished();
    void httpReadyRead();
    void updateDataReadProgress(qint64 bytesRead, qint64 totalBytes);
    void enableDownloadButton();
    void slotAuthenticationRequired(QNetworkReply*,QAuthenticator *);

private:
//    QLabel *statusLabel;
//    QLabel *urlLabel;
//    QLineEdit *urlLineEdit;
    QProgressDialog *progressDialog;
//    QPushButton *downloadButton;
//    QPushButton *quitButton;
//    QDialogButtonBox *buttonBox;

    QUrl url;
    QNetworkAccessManager qnam;
    QNetworkReply *reply;
    QFile *file;
    int httpGetId;
    bool httpRequestAborted;

private:
    Ui::DowmloadWidget *ui;
};

#endif // DOWMLOADWIDGET_H

　　

#include "dowmloadwidget.h"
#include "ui_dowmloadwidget.h"
#include <QFileInfo>
#include <QMessageBox>
#include <QThread>

DowmloadWidget::DowmloadWidget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::DowmloadWidget)
{
    progressDialog = NULL;
    reply = NULL;
    ui->setupUi(this);

    connect(ui->downloadButton, &QPushButton::clicked, this,&DowmloadWidget::downloadFile);
    connect(ui->quitButton, &QPushButton::clicked, this, &DowmloadWidget::cancelDownload);
}

DowmloadWidget::~DowmloadWidget()
{
    delete ui;
}

void DowmloadWidget::startRequest(QUrl url)
{
    reply = qnam.get(QNetworkRequest(url));
    connect(reply, SIGNAL(finished()),this, SLOT(httpFinished()));
    connect(reply, SIGNAL(readyRead()),this, SLOT(httpReadyRead()));
    connect(reply, SIGNAL(downloadProgress(qint64,qint64)),this, SLOT(updateDataReadProgress(qint64,qint64)));
}

void DowmloadWidget::downloadFile()
{
    url = ui->urlLineEdit->text();

    QFileInfo fileInfo(url.path());
    QString fileName = fileInfo.fileName();
//    fileName = "downloadfile.dat";
    if(fileName.isEmpty())
        fileName = "index.html";

    if(QFile::exists(fileName)) {
        if (QMessageBox::question(this, tr("HTTP"),
                                  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 = new QFile(fileName);
    if (!file->open(QIODevice::WriteOnly)) {
        QMessageBox::information(this, tr("HTTP"),
                                 tr("Unable to save the file %1: %2.")
                                 .arg(fileName).arg(file->errorString()));
        delete file;
        file = 0;
        return;
    }

    if(progressDialog == NULL)
    {
        progressDialog = new QProgressDialog(this);
    }
    progressDialog->show();
    progressDialog->setWindowTitle(tr("HTTP"));
    progressDialog->setLabelText(tr("Downloading %1.").arg(fileName));
    ui->downloadButton->setEnabled(false);

    // schedule the request
    httpRequestAborted = false;
    startRequest(url);
}

void DowmloadWidget::cancelDownload()
{
    if(reply == NULL)
        return;
    if(reply->isFinished())
        return;
    reply->abort();
    ui->statusLabel->setText(tr("Download canceled."));
    httpRequestAborted = true;
    ui->downloadButton->setEnabled(true);
}

void DowmloadWidget::httpFinished()
{
    if (httpRequestAborted) {
       if (file) {
           file->close();
           file->remove();
           delete file;
           file = NULL;
       }
       reply->deleteLater();
       progressDialog->hide();
       return;
   }

   progressDialog->hide();
   file->flush();
   file->close();


   QVariant redirectionTarget = reply->attribute(QNetworkRequest::RedirectionTargetAttribute);
   if (reply->error()) {
       file->remove();
       QMessageBox::information(this, tr("HTTP"),
                                tr("Download failed: %1.")
                                .arg(reply->errorString()));
       ui->downloadButton->setEnabled(true);
   } else if (!redirectionTarget.isNull()) {
       QUrl newUrl = url.resolved(redirectionTarget.toUrl());
       if (QMessageBox::question(this, tr("HTTP"),
                                 tr("Redirect to %1 ?").arg(newUrl.toString()),
                                 QMessageBox::Yes | QMessageBox::No) == QMessageBox::Yes) {
           url = newUrl;
           reply->deleteLater();
           file->open(QIODevice::WriteOnly);
           file->resize(0);
           startRequest(url);
           return;
       }
   } else {
       QString fileName = QFileInfo(QUrl(ui->urlLineEdit->text()).path()).fileName();
       ui->statusLabel->setText(tr("Downloaded %1 to current directory.").arg(fileName));
       ui->downloadButton->setEnabled(true);
   }

   reply->deleteLater();
   reply = NULL;
   delete file;
   file = NULL;
}

void DowmloadWidget::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 DowmloadWidget::updateDataReadProgress(qint64 bytesRead, qint64 totalBytes)
{
    if (httpRequestAborted)
        return;

    progressDialog->setMaximum(totalBytes);
    progressDialog->setValue(bytesRead);
}

void DowmloadWidget::enableDownloadButton()
{}

void DowmloadWidget::slotAuthenticationRequired(QNetworkReply*,QAuthenticator *)
{}