QT—基于http协议的网络文件下载

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

#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_NAMESPACEclass http : public QMainWindow
{Q_OBJECTpublic: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_NAMESPACEclass http : public QMainWindow
{Q_OBJECTpublic: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