c++ - Qt 使用 QNetworkAccessManager 执行多个 get

Question

我必须执行很多获取请求，并且必须以不同的方式处理它们。到目前为止，我有这种简单有效的方法:

下面是.h的代码:

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QNetworkAccessManager>
#include <QNetworkRequest>
#include <QNetworkReply>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

private slots:
    void on_pushButton_clicked();

    void on_pushButton_2_clicked();

    void finish(QNetworkReply *reply);

    void finish2(QNetworkReply *reply);

private:
    Ui::MainWindow *ui;
    QNetworkAccessManager* manager;
};

#endif // MAINWINDOW_H

.cpp 的代码:

#include "mainwindow.h"
#include "ui_mainwindow.h"

#include <QDebug>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);    
}

MainWindow::~MainWindow()
{
    delete ui;
}

//First request here...
void MainWindow::on_pushButton_clicked()
{
    manager = new QNetworkAccessManager(this);
    connect(manager, &QNetworkAccessManager::finished, this, &MainWindow::finish);

    manager->get(QNetworkRequest{QUrl{"http://www.link.com/path/"}});
}

//... is completed here
void MainWindow::finish(QNetworkReply *reply) {
    if (reply->error()) {
        ui->lineEdit->setText("error");
        qDebug() << reply->errorString();
    } else {
            ui->lineEdit->setText(QString{reply->readAll()});
    }
}

//Second request here...
void MainWindow::on_pushButton_2_clicked()
{
    manager = new QNetworkAccessManager(this);
    connect(manager, &QNetworkAccessManager::finished, this, &MainWindow::finish2);

    manager->get(QNetworkRequest{QUrl{"https://ergast.com/api/f1/2008/5.json"}});
    qDebug() << "chiamata";
}

//... is completed here
void MainWindow::finish2(QNetworkReply *reply) {
    if (reply->error()) {
        ui->lineEdit_2->setText("error");
        qDebug() << reply->errorString();
    } else {
            ui->lineEdit_2->setText(QString{reply->readAll()});
    }
}

---

当我按下两个按钮时，请求发生但我的 UI 阻塞。我已经尝试过这种方法，因为我在许多示例中看​​到将 QNetworkAccessManager* manager; 作为私有(private)字段并重新使用它是很好的。

顺便说一句，这似乎不是最好的方法。有没有正确的方法来进行多次调用？

我是否应该声明一个 QNetworkAccessManager* 数组并在那里执行所有调用？

---

我还看到可以创建一个名为 QNetworkReply* reply; 的私有(private)字段，然后像这样使用它:

manager = new QNetworkAccessManager(this);  
reply = manager->get(QNetworkRequest{QUrl{"http://www.link.com/path/"}});
connect(manager, &QNetworkReply::finished, this, &MainWindow::finish);

我认为这等同于我正在使用的方法，但在这种情况下我不知道如何处理多个请求，因为我绑定(bind)到 finish 方法并且我应该实现所有那里的逻辑。

Answer 1

我已经测试了你的代码，但我没有注意到 GUI 被阻塞，除了使用信号和槽之外你不应该有那个问题。但是我看到您不必要地创建动态内存，在下面的代码中，我将 QNetworkReply 连接到一个插槽，过滤 QUrl 并删除 QNetworkReply:

*.h

...
private slots:
    void on_pushButton_clicked();
    void on_pushButton_2_clicked();
    void onReplyfinished();

private:
    Ui::MainWindow *ui;
    QNetworkAccessManager *manager;
...

*.cpp

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    manager = new QNetworkAccessManager(this);
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::on_pushButton_clicked()
{
   QNetworkReply *reply = manager->get(QNetworkRequest{QUrl{"http://www.link.com/path/"}});
   connect(reply, &QNetworkReply::finished, this, &MainWindow::onReplyfinished);
}

void MainWindow::on_pushButton_2_clicked()
{
   QNetworkReply *reply = manager->get(QNetworkRequest{QUrl{"https://ergast.com/api/f1/2008/5.json"}});
   connect(reply, &QNetworkReply::finished, this, &MainWindow::onReplyfinished);
}

void MainWindow::onReplyfinished()
{
    QNetworkReply *reply = qobject_cast<QNetworkReply*>(sender());
    if(reply->url() == QUrl{"http://www.link.com/path/"}){
        ui->lineEdit->setText(reply->error() ? "error": reply->readAll());
    }
    else if (reply->url() == QUrl{"https://ergast.com/api/f1/2008/5.json"}){
        ui->lineEdit_2->setText(reply->error() ? "error": reply->readAll());
    }
    reply->deleteLater();
}