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 = );
     ~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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