QT中https文件下载，进度条实现

1.首先在.pro文件中添加支持 

QT       += network

DownLoadFileHttps.h

#ifndef DOWNLOADFILEHTTPS_H
#define DOWNLOADFILEHTTPS_H

#include <memory>
#include <QObject>
#include <QUrl>
#include <QFile>
#include <QDir>
#include <QPointer>
#include <QApplication>
#include <QNetworkReply>
#include <QNetworkAccessManager>
#include <QStandardPaths>
#include "mainwindow.h"

class MainWindow;
class DownLoadFileHttps : public QObject
{
    Q_OBJECT
public:
    // 参数1=下载链接 参数2=保存的路径 参数3=父窗口地址
    explicit DownLoadFileHttps(const QString& downloadUrl, const QString& savePath, QObject* parent = nullptr);
    //析构，不解释
    ~DownLoadFileHttps();

    bool startDownload();  // 开始下载文件
    void cancelDownload(); // 取消下载文件
Q_SIGNALS:
    // 下载进度信号
    void sigProgress(qint64 bytesRead, qint64 totalBytes, qreal progress);
    // 下载完成信号
    void sigDownloadFinished();

private Q_SLOTS:
    // QNetworkReply::finished对应的槽函数
    void httpFinished();
    // QIODevice::readyRead对应的槽函数
    void httpReadyRead();
    // QNetworkReply::downloadProgress对应的槽函数
    void networkReplyProgress(qint64 bytesRead, qint64 totalBytes);

private:
    void startRequest(const QUrl& requestedUrl);
    std::unique_ptr<QFile> openFileForWrite(const QString& fileName);

private:
    // 保存构造时传入的下载url
    QString m_downloadUrl;
    // 保存构造时传入的保存路径
    QString m_savePath;
    // 默认文件名称
    const QString defaultFileName = "QConnect.exe";
    QUrl url;
    QNetworkAccessManager qnam;
    QPointer<QNetworkReply> reply;
    std::unique_ptr<QFile> m_fileptr;
    bool httpRequestAborted;

    MainWindow *m_mainwindow;
};

#endif // DOWNLOADFILEHTTPS_H

DownLoadFileHttps.cpp

#include "DownLoadFileHttps.h"

DownLoadFileHttps::DownLoadFileHttps(const QString& downloadUrl, const QString& savePath, QObject* parent)
    : QObject(parent)
{
    m_downloadUrl = downloadUrl;
    m_savePath    = savePath;
    m_mainwindow = (MainWindow*)parent;
}
DownLoadFileHttps::~DownLoadFileHttps()
{

}
bool DownLoadFileHttps::startDownload()
{
    const QUrl newUrl = QUrl::fromUserInput(m_downloadUrl);

    if (!newUrl.isValid()) {
        qDebug() << QString("Download failed: %1.").arg(reply->errorString());
        return false;
    }
    QString svrloadFile = QStandardPaths::writableLocation(QStandardPaths::DownloadLocation);
    QString fileName = newUrl.fileName();
    //判断文件名称是否正确
    if (fileName.isEmpty())
    {
        fileName = defaultFileName;
    }
    //判断传有路径，没有则默认路径
    if (m_savePath.isEmpty())
    {
        m_savePath = svrloadFile;
    }
    //判断路径是否存在，不存在创建
    if (!QFileInfo(m_savePath).isDir())
    {
        QDir dir;
        dir.mkpath(m_savePath);
    }
    fileName.prepend(m_savePath + '/');
    if (QFile::exists(fileName))//判断是否存在此文件
    {
        QFile::remove(fileName);
    }
    m_fileptr = openFileForWrite(fileName);
    if (!m_fileptr)
        return false;

    startRequest(newUrl);

    return true;
}
void DownLoadFileHttps::cancelDownload()
{
    httpRequestAborted = true;
    reply->abort();
}
void DownLoadFileHttps::httpFinished()
{
    QFileInfo fi;
    if (m_fileptr) {
        fi.setFile(m_fileptr->fileName());
        m_fileptr->close();
        m_fileptr.reset();
    }

    if (httpRequestAborted) {
        return;
    }

    if (reply->error()) {
        QFile::remove(fi.absoluteFilePath());
        qDebug() << QString("Download failed: %1.").arg(reply->errorString());
        return;
    }

    const QVariant redirectionTarget = reply->attribute(QNetworkRequest::RedirectionTargetAttribute);

    if (!redirectionTarget.isNull()) {
        const QUrl redirectedUrl = url.resolved(redirectionTarget.toUrl());
        m_fileptr = openFileForWrite(fi.absoluteFilePath());
        if (!m_fileptr)
        {
            return;
        }
        startRequest(redirectedUrl);
        return;
    }

    Q_EMIT sigDownloadFinished();

    Q_EMIT m_mainwindow->sigDownloadFinished();
}

void DownLoadFileHttps::httpReadyRead()
{
    if (m_fileptr)
        m_fileptr->write(reply->readAll());
}
void DownLoadFileHttps::networkReplyProgress(qint64 bytesRead, qint64 totalBytes)
{
    qreal progress = qreal(bytesRead) / qreal(totalBytes);
    Q_EMIT sigProgress(bytesRead, totalBytes, progress);
    qDebug() << QString::number(progress * 100, 'f', 2) << "%    "
        << bytesRead / (1024 * 1024) << "MB" << "/" << totalBytes / (1024 * 1024) << "MB";
    emit m_mainwindow->sigProgress(bytesRead, totalBytes, progress);
}
void DownLoadFileHttps::startRequest(const QUrl& requestedUrl)
{
    try {
        url = requestedUrl;
        httpRequestAborted = false;
        QSslConfiguration config = QSslConfiguration::defaultConfiguration();
        config.setProtocol(QSsl::AnyProtocol);
        config.setPeerVerifyMode(QSslSocket::VerifyNone);
        QNetworkRequest request = QNetworkRequest(url);
        request.setSslConfiguration(config);
        reply = qnam.get(request);

        connect(reply, &QNetworkReply::finished, this, &DownLoadFileHttps::httpFinished);
        connect(reply, &QIODevice::readyRead, this, &DownLoadFileHttps::httpReadyRead);
        connect(reply, &QNetworkReply::downloadProgress, this, &DownLoadFileHttps::networkReplyProgress);
        //qDebug() << QString(tr("Downloading %1...").arg(url.toString()));
    }
    catch (...)
    {
        return ;
    }

}
std::unique_ptr<QFile> DownLoadFileHttps::openFileForWrite(const QString& fileName)
{
    std::unique_ptr<QFile> file(new QFile(fileName));
    if (!file->open(QIODevice::WriteOnly))
    {
        qDebug() << QString("Unable to save the file %1: %2.")
            .arg(QDir::toNativeSeparators(fileName), file->errorString());
        return nullptr;
    }
    return file;
}

 mainwindow.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>523</width>
    <height>367</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <widget class="QWidget" name="horizontalLayoutWidget">
    <property name="geometry">
     <rect>
      <x>40</x>
      <y>40</y>
      <width>411</width>
      <height>41</height>
     </rect>
    </property>
    <layout class="QHBoxLayout" name="horizontalLayout">
     <item>
      <widget class="QLabel" name="label">
       <property name="text">
        <string>下载Url：</string>
       </property>
      </widget>
     </item>
     <item>
      <widget class="QLineEdit" name="lineEdit"/>
     </item>
     <item>
      <widget class="QPushButton" name="pushButton">
       <property name="text">
        <string>下载</string>
       </property>
      </widget>
     </item>
    </layout>
   </widget>
   <widget class="QProgressBar" name="progressBar">
    <property name="geometry">
     <rect>
      <x>40</x>
      <y>120</y>
      <width>431</width>
      <height>23</height>
     </rect>
    </property>
    <property name="value">
     <number>0</number>
    </property>
   </widget>
   <widget class="QLabel" name="label_2">
    <property name="geometry">
     <rect>
      <x>40</x>
      <y>170</y>
      <width>54</width>
      <height>12</height>
     </rect>
    </property>
    <property name="text">
     <string>日志信息：</string>
    </property>
   </widget>
   <widget class="QLabel" name="label_3">
    <property name="geometry">
     <rect>
      <x>110</x>
      <y>170</y>
      <width>54</width>
      <height>12</height>
     </rect>
    </property>
    <property name="text">
     <string/>
    </property>
   </widget>
  </widget>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>523</width>
     <height>23</height>
    </rect>
   </property>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
 </widget>
 <resources/>
 <connections/>
</ui>

MainWindow调用例子:

MainWindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QStandardPaths>
#include "DownLoadFileHttps.h"
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    connect(this,SIGNAL(sigProgress(qint64, qint64, qreal)),this,SLOT(sltProgress(qint64, qint64, qreal)));
    connect(this,SIGNAL(sigDownloadFinished()),this,SLOT(sltDownloadFinished()));
}

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


void MainWindow::on_pushButton_clicked()
{
    QString svrloadFile = QStandardPaths::writableLocation(QStandardPaths::DownloadLocation);
    DownLoadFileHttps* dT;
    dT = new DownLoadFileHttps(ui->lineEdit->text(), svrloadFile,this);
    dT->startDownload();
}
void MainWindow::sltProgress(qint64 bytesRead, qint64 totalBytes, qreal progress)
{
    ui->progressBar->setValue(progress*100);
    QString title = QString::number(progress*100,'f',2)+"%  "+QString::number(bytesRead/(1024*1024),'f',2)+"MB/"+QString::number(totalBytes/(1024*1024),'f',2)+"MB";
    ui->label_3->setText(title);
}
void MainWindow::sltDownloadFinished()
{
    ui->label_3->setText(tr("下载完成:"));
}

MainWindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();
signals:
    void sigProgress(qint64 bytesRead, qint64 totalBytes, qreal progress);  // 下载进度信号
    void sigDownloadFinished();  // 下载完成信号
private slots:
    void on_pushButton_clicked();
    void sltProgress(qint64 bytesRead, qint64 totalBytes, qreal progress);  // 下载进度信号
    void sltDownloadFinished();  // 下载完成信号
private:
    Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H