QT downloads files (folders) under http addresses through urls

Preface

I have only written about communication through http protocol before, but not about downloading files or folders in http addresses. Let’s learn how to download under QT.

In fact, it is very simple. The same thing as using protocol communication is to create QNetworkAccessManager and QNetworkRequest, set the url of QNetworkRequest, receive the data in QNetworkReply through get request, and use the downloadProgress signal to receive each downloaded content until the download is completed.

code show as below:

 .pro

Mainly adding the network module

#-------------------------------------------------
#
# 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

interface:

 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;
}