qt - 如何通过http下载和保存图像？ [英] qt - how to download and save image via http?

问题描述

我想在控制台应用程序中下载并保存一些图像与Qt。这里是我到目前为止，（所有的代码都是编译，但运行后，似乎不输入 replyFinished（） function ...）

  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<< 别...; 
} 
  

解决方案

使用QNetworkAccessManager

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; 
 
私有插槽：
 void onDownloadProgress（qint64，qint64）; 
 void onFinished（QNetworkReply *）; 
 void onReadyRead（） 
 void onReplyFinished（）; 
}; 
 
 #endif // QDOWNLOADER_H 
  

源文件

  #includeqdownloader.h
 
 QDownloader :: QDownloader（QObject * parent）：
 QObject ）
 {
 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请求; 
 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（文件已成功下载。 
} 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（）; 
} 
} 
  

I am trying to download and save some images with Qt in a console appplication. Here is what I got so far, (all code is compiling, but after run, it seems to don't enter to replyFinished() function...)

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...";
}

解决方案

Download Image using QNetworkAccessManager

header file

#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

source file

#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();
    }
}

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