1.常用到的类

QNetworkAccessManager类用于协调网络操作，负责发送网络请求，创建网络响应

QNetworkReply类表示网络请求的响应。在QNetworkAccessManager发送一个网络请求后创建一个网络响应。它提供了以下信号：

finished()：完成后发出信号

readyRead()：有数据读的数据发出信号

downloadProgress()：表示网络操作进度的信号，有bytesRead和totalBytes两个参数，表示已读取字节数和总字节数

QNetworkReply 是QIODevice的子类，所以QNetworkReply支持流读写功能，也支持异步或同步工作。

2.代码

.h

#ifndef HTTP_H
#define HTTP_H

#include <QMainWindow>
#include <QUrl>
#include <QFile>
#include <QNetworkAccessManager>
#include <QNetworkReply>
QT_BEGIN_NAMESPACE
namespace Ui { class http; }
QT_END_NAMESPACE

class http : public QMainWindow
{
    Q_OBJECT

public:
    http(QWidget *parent = nullptr);
    ~http();

private:
    Ui::http *ui;

    QNetworkAccessManager networkManager;
    QNetworkReply *reply;
    QFile *downFile;

public slots:
    void on_finished();
    void on_readyRead();
    void  downLoadProgress(qint64 bytesRead,qint64 totalBytes);
private slots:
    void on_pushButton_2_clicked();
    void on_pushButton_clicked();
};
#endif // HTTP_H
#ifndef HTTP_H
#define HTTP_H

#include <QMainWindow>
#include <QUrl>
#include <QFile>
#include <QNetworkAccessManager>
#include <QNetworkReply>
QT_BEGIN_NAMESPACE
namespace Ui { class http; }
QT_END_NAMESPACE

class http : public QMainWindow
{
    Q_OBJECT

public:
    http(QWidget *parent = nullptr);
    ~http();

private:
    Ui::http *ui;

    QNetworkAccessManager networkManager;
    QNetworkReply *reply;
    QFile *downFile;

public slots:
    void on_finished();
    void on_readyRead();
    void  downLoadProgress(qint64 bytesRead,qint64 totalBytes);
private slots:
    void on_pushButton_2_clicked();
    void on_pushButton_clicked();
};
#endif // HTTP_H

.cpp

#include "http.h"
#include "ui_http.h"
#include<QDir>
http::http(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::http)
{
    ui->setupUi(this);
}

http::~http()
{
    delete ui;
}

void http::on_finished()
{
    QFileInfo fileInfo;
       fileInfo.setFile(downFile->fileName());
       downFile->close();
       delete downFile;
       reply->deleteLater();
       reply = nullptr;

       ui->pushButton->setEnabled(true);

}
void http::on_readyRead()
{
    downFile->write(reply->readAll());
}

void http::downLoadProgress(qint64 bytesRead, qint64 totalBytes)
{
    ui->progressBar->setMaximum(totalBytes);
    ui->progressBar->setValue(bytesRead);
}


void http::on_pushButton_2_clicked()
{
    //缺省路径
        QString curPath = QDir::currentPath();

        QDir dir(curPath);
        QString sub = "temp";
        dir.mkdir(sub);

        ui->lineEdit_2->setText(curPath + "/" + sub + "/");

}

void http::on_pushButton_clicked()
{

    //下载
    QString url = ui->lineEdit->text().trimmed();

       if(url.isEmpty())
           return;

       QUrl newUrl = QUrl::fromUserInput(url);
       if(!newUrl.isValid())
           return;

       QString tempDir = ui->lineEdit_2->text().trimmed();
       if(tempDir.isEmpty())
           return;

       QString fullFileName = tempDir+newUrl.fileName();
       if(QFile::exists(fullFileName))
           QFile::remove(fullFileName);

       downFile = new QFile(fullFileName);
       if(!downFile->open(QIODevice::WriteOnly))
           return;

       ui->pushButton->setEnabled(false);

       reply = networkManager.get(QNetworkRequest(newUrl));
       connect(reply,&QNetworkReply::finished,this,&http::on_finished);
       connect(reply,&QNetworkReply::readyRead,this,&http::on_readyRead);
       connect(reply,&QNetworkReply::downloadProgress,this,&http::downLoadProgress);


}

结果：

点击缺省路径，保存文件

在地址栏输入下载的文件地址，例：下载网易云音乐logo图片，地址如下

http://p3.music.126.net/tBTNafgjNnTL1KlZMt7lVA==/18885211718935735.jpg

原文链接：https://blog.csdn.net/wzz953200463/article/details/123858775