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:

 1 #ifndef MAINWINDOW_H
 2 #define MAINWINDOW_H
 3 
 4 #include <QMainWindow>
 5 #include <QtNetWork>
 6 
 7 namespace Ui
 8 {
 9 class MainWindow;
10 }
11 
12 class MainWindow : public QMainWindow
13 {
14     Q_OBJECT
15 
16 public:
17     explicit MainWindow(QWidget *parent = 0);
18     ~MainWindow();
19 
20 private:
21     void get(QUrl u);
22 
23 private slots:
24     void on_pushButton_clicked();
25     void finished();
26 
27 private:
28     Ui::MainWindow *ui;
29 
30     QUrl m_url;
31     QString m_htmlText;
32     QNetworkReply *m_pReply;
33     QNetworkAccessManager m_manager;
34 };
35 
36 #endif // MAINWINDOW_H

文件2：

 1 #include "mainwindow.h"
 2 #include "ui_mainwindow.h"
 3 
 4 MainWindow::MainWindow(QWidget *parent) :
 5     QMainWindow(parent),
 6     ui(new Ui::MainWindow),
 7     m_pReply(Q_NULLPTR)
 8 {
 9     ui->setupUi(this);
10 }
11 
12 MainWindow::~MainWindow()
13 {
14     delete ui;
15 }
16 
17 void MainWindow::get(QUrl u)
18 {
19     m_url = u;
20 
21     if (m_pReply != Q_NULLPTR)
22     { // 更改reply指向位置前一定要保证之前的定义了自动delete
23         m_pReply->deleteLater();
24     }
25 
26     QNetworkRequest request;
27     request.setUrl(m_url);
28     m_pReply = m_manager.get(request);
29     qDebug() << "start get";
30     connect(m_pReply, &QNetworkReply::finished, this, &MainWindow::finished);
31 }
32 
33 void MainWindow::finished()
34 {
35     QByteArray bytes = m_pReply->readAll();
36 
37     m_pReply->deleteLater();
38     m_pReply = Q_NULLPTR;
39 
40     const QVariant redirectionTarget = m_pReply->attribute(QNetworkRequest::RedirectionTargetAttribute);
41     if (!redirectionTarget.isNull())
42     { //如果网址跳转重新请求
43         const QUrl redirectedUrl = m_url.resolved(redirectionTarget.toUrl());
44         qDebug() << "redirectedUrl:" << redirectedUrl.url();
45         get(redirectedUrl);
46         return;
47     }
48 
49     qDebug() << "finished";
50     m_htmlText = bytes;
51     qDebug() << "get ready,read size:" << m_htmlText.size();
52 
53     // 写入文件
54     QFile f("result.html");
55     f.open(QFile::WriteOnly);
56     f.write(bytes);
57 }
58 
59 void MainWindow::on_pushButton_clicked()
60 {
61     m_htmlText = "";
62     get(QUrl("http://www.baidu.com/"));
63 }