目錄

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官方解析

博主例子

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官方解析

QNetworkAccessMangager類運行應用程序回復和接收網絡包。

QNetworkAccessManager是一套API庫，可以發包，設置代理，內存配置等。可以用于網絡的應答（如http協議）。

如下面這個偽代碼的栗子：

QNetworkAccessManager *manager = new QNetworkAccessManager(this);connect(manager, SIGNAL(finished(QNetworkReply*)),this, SLOT(replyFinished(QNetworkReply*)));manager->get(QNetworkRequest(QUrl("http://qt-project.org")));

注意：這是一個異步的API。

當請求完成后，用戶需要手動刪除QNetworkReply對象，這里要注意，不應該在finished()信號過來的時候刪除，而應該使用deleteLater()函數。

如果要并行處理，這里取決于平臺，目前桌面平臺支持6個并行。

如下面這個設置User-Agent的栗子：

QNetworkRequest request;request.setUrl(QUrl("http://qt-project.org"));request.setRawHeader("User-Agent", "MyOwnBrowser 1.0");QNetworkReply *reply = manager->get(request);connect(reply, SIGNAL(readyRead()), this, SLOT(slotReadyRead()));connect(reply, SIGNAL(error(QNetworkReply::NetworkError)),this, SLOT(slotError(QNetworkReply::NetworkError)));connect(reply, SIGNAL(sslErrors(QList<QSslError>)),this, SLOT(slotSslErrors(QList<QSslError>)));

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博主例子

現在舉一個下載http網站中web主頁的例子，注意了是http的協議，不是https的協議！！！

程序運行截圖如下：

程序結構如下：

源碼如下：

widget.h

#ifndef WIDGET_H #define WIDGET_H#include <QWidget>QT_BEGIN_NAMESPACE class QNetworkAccessManager; class QNetworkReply; QT_END_NAMESPACEnamespace Ui { class Widget; }class Widget : public QWidget {Q_OBJECTpublic:explicit Widget(QWidget *parent = 0);~Widget();protected slots:void replyFinished(QNetworkReply *reply);void netWorkReplyLoadProgress(qint64 received, qint64 total);void deleteNetWorkReply();private:Ui::Widget *ui;QNetworkAccessManager *m_manager;QNetworkReply *m_netWorkReply; };#endif // WIDGET_H

main.cpp

#include "widget.h" #include <QApplication>int main(int argc, char *argv[]) {QApplication a(argc, argv);Widget w;w.show();return a.exec(); }

widget.cpp

#include "widget.h" #include "ui_widget.h"#include <QNetworkAccessManager> #include <QNetworkReply> #include <QDebug> #include <QNetworkReply>Widget::Widget(QWidget *parent) :QWidget(parent),ui(new Ui::Widget) {ui->setupUi(this);m_manager = new QNetworkAccessManager(this);connect(m_manager, SIGNAL(finished(QNetworkReply*)), this, SLOT(replyFinished(QNetworkReply*)));QUrl url("http://www.it1995.cn/");m_netWorkReply = m_manager->get(QNetworkRequest(url));connect(m_netWorkReply, SIGNAL(downloadProgress(qint64,qint64)), this, SLOT(netWorkReplyLoadProgress(qint64,qint64)));}Widget::~Widget() {delete ui; }void Widget::replyFinished(QNetworkReply *reply) {qDebug() << "replyFinished called!";qDebug() << "reply->readAll():" << QString::fromUtf8(reply->readAll());m_netWorkReply->deleteLater(); //此列子中 m_netWorkReply->deleteLater(); 與 delete m_netWorkReply; 沒有什么區別 }void Widget::netWorkReplyLoadProgress(qint64 received, qint64 total) {qDebug() << "received:" << received << " total:" << total; }void Widget::deleteNetWorkReply() {qDebug() << "deleteNetWorkReply called!" << endl; }

此處可以提升一下，在replyFinished這個函數里面，如果要把網頁保存，那些這么做會，這個函數占用大量的CUP和內存（如果此處并行保存6個100MB的文件），在這里可以在QNetworkReply類中的readyRead這個信號關聯后進行，因為網絡傳輸數據太大，會被拆分，如下所示：

本例子下載的網頁比較小，現象不明顯，

把widget.cpp改成如下就明顯了：

#include "widget.h" #include "ui_widget.h"#include <QNetworkAccessManager> #include <QNetworkReply> #include <QDebug> #include <QNetworkReply>Widget::Widget(QWidget *parent) :QWidget(parent),ui(new Ui::Widget) {ui->setupUi(this);m_manager = new QNetworkAccessManager(this);connect(m_manager, SIGNAL(finished(QNetworkReply*)), this, SLOT(replyFinished(QNetworkReply*)));QUrl url("http://www.it1995.cn/");m_netWorkReply = m_manager->get(QNetworkRequest(url));connect(m_netWorkReply, SIGNAL(downloadProgress(qint64,qint64)), this, SLOT(netWorkReplyLoadProgress(qint64,qint64)));connect(m_netWorkReply, SIGNAL(readyRead()), this, SLOT(httpRead()));}Widget::~Widget() {delete ui; }void Widget::replyFinished(QNetworkReply *reply) {qDebug() << "replyFinished called!";//qDebug() << "reply->readAll():" << QString::fromUtf8(reply->readAll());m_netWorkReply->deleteLater(); //此列子中 m_netWorkReply->deleteLater(); 與 delete m_netWorkReply; 沒有什么區別 }void Widget::netWorkReplyLoadProgress(qint64 received, qint64 total) {qDebug() << "received:" << received << " total:" << total; }void Widget::deleteNetWorkReply() {qDebug() << "deleteNetWorkReply called!" << endl; }void Widget::httpRead() {qDebug() << "111"; }

運行截圖如下：

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此處把httpRead()修改如下，再看看運行結果：

void Widget::httpRead() {qDebug() << m_netWorkReply->readAll(); }

運行截圖和最開始的一樣，可以用這個思路去保存文件！減少內存和CPU的使用！

這里來看看此時發送的Http數據包頭：

修改源碼，生成User-Agent屬性，

添加這幾行行即可：

Widget::Widget(QWidget *parent) :QWidget(parent),ui(new Ui::Widget) {ui->setupUi(this);m_manager = new QNetworkAccessManager(this);connect(m_manager, SIGNAL(finished(QNetworkReply*)), this, SLOT(replyFinished(QNetworkReply*)));QNetworkRequest request;request.setUrl(QUrl("http://www.it1995.cn/"));request.setRawHeader("User-Agent", "I am fine, fuck you");m_netWorkReply = m_manager->get(request);connect(m_netWorkReply, SIGNAL(downloadProgress(qint64,qint64)), this, SLOT(netWorkReplyLoadProgress(qint64,qint64)));connect(m_netWorkReply, SIGNAL(readyRead()), this, SLOT(httpRead()));}

包頭如下：

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