QNetworkAccessManager

【1】头文件

想要利用QNetworkAccessManager类，必须在pro文件中添加对应库network，如下：

QT += network

如果利用的VS + QT开发环境，请参考随笔《Qt添加QtNetwork库文件》

【2】示例文件

文件1:

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QtNetWork>

namespace Ui
{
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

private:
    void get(QUrl u);

private slots:
    void on_pushButton_clicked();
    void finished();

private:
    Ui::MainWindow *ui;

    QUrl m_url;
    QString m_htmlText;
    QNetworkReply *m_pReply;
    QNetworkAccessManager m_manager;
};

#endif // MAINWINDOW_H

文件2：

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

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

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

void MainWindow::get(QUrl u)
{
    m_url = u;

    if (m_pReply != Q_NULLPTR)
    { // 更改reply指向位置前一定要保证之前的定义了自动delete
        m_pReply->deleteLater();
    }

    QNetworkRequest request;
    request.setUrl(m_url);
    m_pReply = m_manager.get(request);
    qDebug() << "start get";
    connect(m_pReply, &QNetworkReply::finished, this, &MainWindow::finished);
}

void MainWindow::finished()
{
    QByteArray bytes = m_pReply->readAll();

    m_pReply->deleteLater();
    m_pReply = Q_NULLPTR;

    const QVariant redirectionTarget = m_pReply->attribute(QNetworkRequest::RedirectionTargetAttribute);
    if (!redirectionTarget.isNull())
    { //如果网址跳转重新请求
        const QUrl redirectedUrl = m_url.resolved(redirectionTarget.toUrl());
        qDebug() << "redirectedUrl:" << redirectedUrl.url();
        get(redirectedUrl);
        return;
    }

    qDebug() << "finished";
    m_htmlText = bytes;
    qDebug() << "get ready,read size:" << m_htmlText.size();

    // 写入文件
    QFile f("result.html");
    f.open(QFile::WriteOnly);
    f.write(bytes);
}

void MainWindow::on_pushButton_clicked()
{
    m_htmlText = "";
    get(QUrl("http://www.baidu.com/"));
}

返回的结果文件：

在运行目录中查找result.html文件，双击运行，然后与百度首页作对比，可以发现get获取的数据中不包含图片信息。

【3】总结

示例程序很简单，主要应用QNetworkAccessManager类的get接口。

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