QT中通过HTTP URL获取并保存网页上的图片

来源：互联网发布：网络信息安全的概念编辑：程序博客网时间：2024/05/01 21:06

通过HTTP来获得网页上的图片，在MFC中主要是通过类CInternetSession类完成，在QT中则是通过三个类来完成，QNetworkAccessManager,QNetworkRequest,QNetworkReply，三个类的详细用法还需自己多看文档，这里就不多解释了，下面直接贴代码，采用的是两种方式来实现的，一个类和一个函数，别忘了在Qt工程中加入 QT += core network.

#ifndef DOWNLOADER_H#define DOWNLOADER_H#include <QFile>#include <QNetworkAccessManager>#include <QNetworkRequest>#include <QNetworkReply>#include <QObject>#include <QUrl>class Downloader : public QObject {    Q_OBJECT    QFile *m_file;    bool m_isReady;public:    explicit Downloader(QObject *parent = 0) : QObject(parent) {m_isReady = true;}    virtual ~Downloader() {}    void downloadFileFromURL(const QString &url, const QString &filePath);private slots:    void onDownloadFileComplete(QNetworkReply *reply);};QNetworkReply::NetworkError downloadURL(const QString &url, const QString &fileName);#endif // DOWNLOADER_H

#include "downloader.h"#include <QDebug>#include <QEventLoop>void Downloader::downloadFileFromURL(const QString &url, const QString &filePath){    if (!m_isReady)        return;    m_isReady = false;    const QString fileName = filePath + url.right(url.size() - url.lastIndexOf("/"));    qDebug() << fileName;    m_file = new QFile();    m_file->setFileName(fileName);    m_file->open(QIODevice::WriteOnly);    if (!m_file->isOpen()) {        m_isReady = true;        return;    }    QNetworkAccessManager *manager = new QNetworkAccessManager;    QNetworkRequest request;    request.setUrl(QUrl(url));    connect(manager, SIGNAL(finished(QNetworkReply *)), this, SLOT(onDownloadFileComplete(QNetworkReply *)));    manager->get(request);}void Downloader::onDownloadFileComplete(QNetworkReply *reply){    if (!m_file->isWritable()) {        m_isReady = true;        return;    }    m_file->write(reply->readAll());    m_file->close();    m_isReady = true;}bool downloadURL(const QString &url, const QString &fileName){    QNetworkAccessManager manager;    QNetworkRequest request;    request.setUrl(url);    QNetworkReply *reply = manager.get(request);    QEventLoop loop;    QObject::connect(reply, SIGNAL(finished()), &loop, SLOT(quit()));    loop.exec();    if (reply->error() != QNetworkReply::NoError)    {        return false;    }    QFile f(fileName);    qDebug() << fileName;    if(!f.open(QIODevice::WriteOnly))        return false;    f.write(reply->readAll());    f.close();    delete reply;    return true; }

下面是测试代码：

#include <QCoreApplication>#include "downloader.h"int main(int argc, char *argv[]){    QCoreApplication a(argc, argv);//    Downloader downloader;//    downloader.downloadFileFromURL("https://img3.doubanio.com/view/photo/photo/public/p449668815.jpg",//                                   "G:/Documents/picture");    downloadURL("https://img3.doubanio.com/view/photo/photo/public/p449668815.jpg",                                                   "G:/Documents/picture/p449668815.<span style="font-family: Arial, Helvetica, sans-serif;">jpg");</span>    return a.exec();}

上面的路径G:/Documents/picture/你得先建立这个路径，如果你的需求是路径不存在则先新建，那么需要在程序中加几句代码来实现，也是比较简单的。

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