Qt HTTP下载数据

添加头文件：

#include    
#include    
#include    
#include    

创建对象：

QNetworkAccessManager networkManager;//网络管理
    QNetworkReply *reply;   //网络响应
    QFile *downloadedFile;//下载保存的临时文件

输入url地址：

QUrl newUrl = QUrl::fromUserInput(urlSpec);//URL地址

创建临时文件：

downloadedFile =new QFile(fullFileName);
if (!downloadedFile->open(QIODevice::WriteOnly))
    {
        QMessageBox::information(this, tr("错误"),"临时文件打开错误");

发送请求，创建网络响应：

reply = networkManager.get(QNetworkRequest(newUrl));

连接信号与槽：

connect(reply, SIGNAL(finished()), this, SLOT(on_finished()));
    connect(reply, SIGNAL(readyRead()), this, SLOT(on_readyRead()));
    connect(reply, SIGNAL(downloadProgress(qint64,qint64)),
            this, SLOT(on_downloadProgress(qint64,qint64)));


void MainWindow::on_finished()
{//网络响应结束
    QFileInfo fileInfo;
    fileInfo.setFile(downloadedFile->fileName());

    downloadedFile->close();
    delete downloadedFile;
    downloadedFile = Q_NULLPTR;

    reply->deleteLater(); //
    reply = Q_NULLPTR;

    if (ui->checkOpen->isChecked())//打开下载的文件
        QDesktopServices::openUrl(QUrl::fromLocalFile(fileInfo.absoluteFilePath()));

    ui->btnDownload->setEnabled(true);
}

void MainWindow::on_readyRead()
{//读取下载的数据
    downloadedFile->write(reply->readAll());
}

void MainWindow::on_downloadProgress(qint64 bytesRead, qint64 totalBytes)
{//下载进程
    ui->progressBar->setMaximum(totalBytes);
    ui->progressBar->setValue(bytesRead);
}