qt - 如何通过 http 下载和保存图像？

Question

我正在尝试在控制台应用程序中使用 Qt 下载并保存一些图像。这是我到目前为止得到的，（所有代码正在编译，但运行后，似乎没有进入 replyFinished() 函数……）

 void Test::start()
{
    std::cout << "start1";
    QNetworkAccessManager *manager = new QNetworkAccessManager();
    connect(manager, SIGNAL(finished(QNetworkReply*)), this, SLOT(replyFinished(QNetworkReply*)));
    manager->get(QNetworkRequest(QUrl("http://www.exylum.mydevil.net/firefox.jpg")));
}

void Test::replyFinished(QNetworkReply* reply)
{
    std::cout << "st";
    QImage* img2 = new QImage();
    img2->loadFromData(reply->readAll());

    if(img2->isNull())
        std::cout << "oops";

    if(img2->save("omg2.jpg", "JPG"))
        std::cout << "saved";
    else
        std::cout << "dont...";
}

原文由 aaaomg 发布，翻译遵循 CC BY-SA 4.0 许可协议

Answer 1

使用 QNetworkAccessManager 下载图像

头文件

#ifndef QDOWNLOADER_H
#define QDOWNLOADER_H

#include <QObject>
#include <QNetworkAccessManager>
#include <QNetworkRequest>
#include <QNetworkReply>
#include <QFile>
#include <QStringList>

class QDownloader : public QObject
{
    Q_OBJECT
public:
    explicit QDownloader(QObject *parent = 0);
    virtual ~QDownloader();
    void setFile(QString fileURL);

private:
    QNetworkAccessManager *manager;
    QNetworkReply *reply;
    QFile *file;

private slots:
    void onDownloadProgress(qint64,qint64);
    void onFinished(QNetworkReply*);
    void onReadyRead();
    void onReplyFinished();
};

#endif // QDOWNLOADER_H

源文件

#include "qdownloader.h"

QDownloader::QDownloader(QObject *parent) :
    QObject(parent)
{
    manager = new QNetworkAccessManager;
}

QDownloader::~QDownloader()
{
    manager->deleteLater();
}

void QDownloader::setFile(QString fileURL)
{
    QString filePath = fileURL;
    QString saveFilePath;
    QStringList filePathList = filePath.split('/');
    QString fileName = filePathList.at(filePathList.count() - 1);
    saveFilePath = QString("C:/Images/" + fileName );

    QNetworkRequest request;
    request.setUrl(QUrl(fileURL));
    reply = manager->get(request);

    file = new QFile;
    file->setFileName(saveFilePath);
    file->open(QIODevice::WriteOnly);

    connect(reply,SIGNAL(downloadProgress(qint64,qint64)),this,SLOT(onDownloadProgress(qint64,qint64)));
    connect(manager,SIGNAL(finished(QNetworkReply*)),this,SLOT(onFinished(QNetworkReply*)));
    connect(reply,SIGNAL(readyRead()),this,SLOT(onReadyRead()));
    connect(reply,SIGNAL(finished()),this,SLOT(onReplyFinished()));
}

void QDownloader::onDownloadProgress(qint64 bytesRead,qint64 bytesTotal)
{
    qDebug(QString::number(bytesRead).toLatin1() +" - "+ QString::number(bytesTotal).toLatin1());
}

void QDownloader::onFinished(QNetworkReply * reply)
{
    switch(reply->error())
    {
        case QNetworkReply::NoError:
        {
            qDebug("file is downloaded successfully.");
        }break;
        default:{
            qDebug(reply->errorString().toLatin1());
        };
    }

    if(file->isOpen())
    {
        file->close();
        file->deleteLater();
    }
}

void QDownloader::onReadyRead()
{
    file->write(reply->readAll());
}

void QDownloader::onReplyFinished()
{
    if(file->isOpen())
    {
        file->close();
        file->deleteLater();
    }
}

原文由 Lwin Htoo Ko 发布，翻译遵循 CC BY-SA 3.0 许可协议