QT QNetworkAccessManager and Signals

QT QNetworkAccessManager and Signals

本文关键字：Signals and QNetworkAccessManager QT      更新时间：2023-10-16

我有一个类(RequestHandler)，我从我的主应用程序类调用它来调用各种Web服务。一旦服务完成，类就会向调用类发送一个信号，表示它已完成(可能带有 QString 消息)。我有信号在测试方法中工作，但QNetworkAccessManager根本不起作用。我对QT和C++很陌生。感谢您的帮助。

RequestHandler.h

#ifndef REQUESTHANDLER_H_
#define REQUESTHANDLER_H_
#include <QNetworkAccessManager>
#include <QUrl>
#include <QNetworkRequest>
#include <QNetworkReply>
#include <QOBJECT>
#include "MainAppClass.hpp"
class RequestHandler : public QObject
{
Q_OBJECT
public:
explicit RequestHandler(QObject *parent = 0);
void validateRegistration(QString reg);
void onStatusUpdateCompleted();
void sayHi();
signals:
void sendSignal(QString txt);
private:
QNetworkAccessManager* manager;
QObject* thisObj;
public slots:
void onRequestCompleted();
};
#endif /* REQUESTHANDLER_H_ */

请求处理程序.cpp

#include "RequestHandler.h"
RequestHandler::RequestHandler(QObject *parent) : QObject(parent)
{
thisObj= parent;
}
void RequestHandler::validateRegistration(QString reg) {
QNetworkRequest request;
request.setUrl(QUrl("the_registration_url"));
manager = new QNetworkAccessManager();
QNetworkReply *reply = manager->get(request);
connect(reply, SIGNAL(finished()), this, SLOT(onRequestCompleted()));
}
void RequestHandler::onRequestCompleted() {
// not getting here at all
}
void RequestHandler::sayHi()
{
// this is working
QObject::connect(this, SIGNAL(sendSignal(QString)), thisCellCast,   SLOT(recieveValue(QString)));
emit sendSignal("HERES THE SIGNAL");
}

我这样称呼这个类：

// test slots and reg
RequestHandler rh(this);
//working
rh.sayHi();
// not working
rh.validateRegistration("test");

感谢您的帮助。

通常应该QNetworkAccessManager通过连接到error()和finished()信号，以便在发生错误时通知您。

在validateRegistration()中构造QNetworkAccessManager对象真是个坏主意，因为它会导致内存泄漏，并且您只需要一个这样的对象 类。所以在RequestHandler的构造函数中这样做。

void RequestHandler::validateRegistration(QString reg)
{
QUrl url("the_registration_url");
QNetworkRequest request(url);
QNetworkReply *reply = manager->get(request);
connect(reply, SIGNAL(finished()), SLOT(onRequestCompleted()));
connect(reply, SIGNAL(error(QNetworkReply::NetworkError)),
SLOT(onError(QNetworkReply::NetworkError)));
}
void RequestHandler::onRequestCompleted()
{
qDebug() << "Request succeeded";
}
void RequestHandler::onError(QNetworkReply::NetworkError code)
{
qError() << "Request failed with code " << code;
}

还要确保在某处调用了 QApplication：：exec()，以便运行主事件循环。

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