前言
之前只写过通过http协议通信，没有写过下载http地址中的文件或者文件夹，了解一下在QT下如何下载。
其实很简单，同使用协议通信相同的是，创建QNetworkAccessManager和QNetworkRequest，设置QNetworkRequest的url，通过get请求接收QNetworkReply中数据，利用downloadProgress信号接收每次下载下来的内容，直到下载完成。
代码如下：
.pro
主要是加上network模块
#-------------------------------------------------
#
# Project created by QtCreator 2023-10-26T18:29:32
#
#-------------------------------------------------QT += core gui networkgreaterThan(QT_MAJOR_VERSION, 4): QT += widgetsTARGET = load_http_file
TEMPLATE = app# The following define makes your compiler emit warnings if you use
# any feature of Qt which has been marked as deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS# You can also make your code fail to compile if you use deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000 # disables all the APIs deprecated before Qt 6.0.0SOURCES += \main.cpp \widget.cpp \HEADERS += \widget.h \FORMS += \widget.ui
界面：
widget.h
#ifndef WIDGET_H
#define WIDGET_H#include <QWidget>
#include <QFile>
#include <QUrl>
#include <QNetworkReply>
#include <QNetworkRequest>
#include <QNetworkAccessManager>
#include <QEventLoop>
#include <QTimer>namespace Ui {
class Widget;
}class Widget : public QWidget
{Q_OBJECTpublic:explicit Widget(QWidget *parent = 0);~Widget();bool downloadFile(QString url);
private slots:void on_load_zip_clicked();private:Ui::Widget *ui;private:bool flag_download = false;
};#endif // WIDGET_Hwidget.cpp
#include "widget.h"
#include <QDir>
#include <QThread>Widget::Widget(QWidget *parent) :QWidget(parent),ui(new Ui::Widget)
{}Widget::~Widget()
{delete ui;
}void Widget::on_load_zip_clicked()
{downloadFile(ui->lineEdit_url->text());
}bool Widget::downloadFile(QString url)
{if(flag_download){qDebug()<<"有正在下载中的文件，已停止当前下载。";return false;}int timeout = 1000 * 60; //* 3;QString path = "3D";QDir dir(path);if(!dir.exists()){if(!dir.mkdir(dir.absolutePath())){qDebug()<<"创建3D文件夹失败！";return false;}}path = path + "/" + url.section('/',-1,-1);qDebug()<<"url:"<<url<<" path:"<<path;QFile file(path);if (!file.open(QIODevice::WriteOnly)){qDebug()<<"打开待下载文件失败！";return false;}flag_download = true;QNetworkAccessManager networkManager;QNetworkRequest request;request.setUrl(QUrl(url));QNetworkReply *reply = networkManager.get(request);QTimer timer;QEventLoop eventLoop;connect(reply, &QNetworkReply::downloadProgress, [=, &file, &timer](qint64 bytesReceived,qint64 bytesTotal){qDebug()<<"当前下载的文件大小："<<bytesReceived<<" 总文件大小："<<bytesTotal;if (timer.isActive())timer.start(timeout);file.write(reply->readAll());});connect(reply, &QNetworkReply::finished, &timer, &QTimer::stop);connect(reply, &QNetworkReply::finished, &eventLoop, &QEventLoop::quit);connect(&timer, &QTimer::timeout, &eventLoop, &QEventLoop::quit);timer.start(timeout);eventLoop.exec();//QEventLoop::ExcludeUserInputEventsflag_download = false;if (reply->error() != QNetworkReply::NoError){qDebug()<<"请求失败！失败原因："<<reply->error();file.close();delete reply;return false;}if(timer.isActive()){qDebug()<<"请求超时！";timer.stop();file.close();delete reply;return false;}qDebug()<<"下载3D文件成功！";file.close();delete reply;return true;
}
