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 network

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = 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 6.0.0


SOURCES += \
        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_OBJECT

public:
    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_H

widget.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::ExcludeUserInputEvents

    flag_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;
}