c++ - QNetworkAccessManager 问题获取网页

Question

我正在尝试使用以下代码下载网页的源代码头文件:

#include <QObject>
#include <QHttp>
#include <QtNetwork>
#include <QFile>
#include <QDebug>

class CDownloader : public QObject
{
  Q_OBJECT
public:
  explicit CDownloader(QObject *parent = 0);

void Do_Download();

signals:

public slots:
  void result(QNetworkReply*);
private:   
  QNetworkAccessManager *manager;
  QNetworkReply *reply;
  QNetworkAccessManager qnam;
};

#endif // CDOWNLOADER_H

和源文件:

#include "cdownloader.h"

CDownloader::CDownloader(QObject *parent) :
QObject(parent)
{    
}

void CDownloader::Do_Download()
{
  manager = new QNetworkAccessManager(this);
  connect(manager, SIGNAL(finished(QNetworkReply*)), this, SLOT(result(QNetworkReply*)));
  manager->get(QNetworkRequest(QUrl("http://www.google.com")));
}

void CDownloader::result(QNetworkReply *reply)
{
     qDebug() << "loading complete";
}

和按钮代码:

void MainWindow::on_download_clicked()
{
  CDownloader cDown;
  cDown.Do_Download(); 
} 

但 qDebug 永远不会在结果槽中调用。我错过了什么？

Answer 1

void MainWindow::on_download_clicked()
{
  CDownloader cDown;
  cDown.Do_Download(); 
}

当该方法返回时，cDown 立即被销毁。至少只要您还没有收到和处理回复，您就需要让该对象保持事件状态。

为此，cDown 应该是您的 MainWindow 的成员，或者指向(或指针集合)CDownloader 的指针应该在您的代码中的某处进行维护(并妥善处置)。