105_Qt的HTTP编程

105 Qt的HTTP编程

105.1 Qt的HTTP类

为支持基于HTTP协议的网络编程，Qt提供了以下类：

与HTTP有关的类	功能描述
QNetworkRequest	面向URL的网络请求，包括请求的内容，目前支持HTTP、FTP等
QNetworkAccessManager	协调网络操作，实际执行发送请求和接收响应的动作
QNetworkReply	表示网络响应，借助downloadProgress、readyRead和finished等信号，监测网络响应的传输情况，并执行相应操作

105.2 案例

105.2.1 创建项目

通过QtCreator，在C:\Users\Minwei\Projects\Qt路径下，创建名为Downloader的项目。

105.2.2 设计界面

C:\Users\Minwei\Projects\Qt\Downloader\downloaderdialog.ui：


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<?xml version="1.0" encoding="UTF-8"?>
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<ui version="4.0">
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 <class>DownloaderDialog</class>
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 <widget class="QDialog" name="DownloaderDialog">
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  <property name="geometry">
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   <rect>
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    <x>0</x>
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    <y>0</y>
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    <width>600</width>
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    <height>100</height>
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   </rect>
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  </property>
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  <property name="windowTitle">
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   <string>HTTP下载器</string>
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  </property>
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  <layout class="QVBoxLayout" name="m_layoutVer">
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   <item>
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    <spacer name="m_spacerUp">
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     <property name="orientation">
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      <enum>Qt::Vertical</enum>
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     </property>
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     <property name="sizeHint" stdset="0">
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      <size>
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       <width>20</width>
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       <height>74</height>
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      </size>
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     </property>
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    </spacer>
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   </item>
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   <item>
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    <layout class="QGridLayout" name="m_layoutGrid">
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     <item row="0" column="0">
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      <widget class="QLabel" name="m_labUrl">
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       <property name="text">
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        <string>URL：</string>
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       </property>
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      </widget>
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     </item>
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     <item row="0" column="1">
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      <widget class="QLineEdit" name="m_editUrl">
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       <property name="text">
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        <string>http://www.sqlite.org/2021/sqlite-dll-win32-x86-3360000.zip</string>
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       </property>
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      </widget>
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     </item>
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     <item row="0" column="2">
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      <widget class="QPushButton" name="m_btnDownload">
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       <property name="text">
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        <string>下载</string>
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       </property>
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       <property name="default">
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        <bool>true</bool>
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       </property>
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      </widget>
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     </item>
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     <item row="1" column="0">
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      <widget class="QLabel" name="m_labPath">
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       <property name="text">
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        <string>路径：</string>
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       </property>
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      </widget>
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     </item>
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     <item row="1" column="1">
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      <widget class="QLineEdit" name="m_editPath"/>
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     </item>
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     <item row="1" column="2">
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      <widget class="QPushButton" name="m_btnDefault">
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       <property name="text">
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        <string>默认</string>
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       </property>
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      </widget>
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     </item>
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     <item row="2" column="0">
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      <widget class="QLabel" name="m_labProgress">
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       <property name="text">
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        <string>进度：</string>
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       </property>
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      </widget>
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     </item>
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     <item row="2" column="1">
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      <widget class="QProgressBar" name="m_progressBar">
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       <property name="value">
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        <number>0</number>
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       </property>
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      </widget>
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     </item>
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     <item row="2" column="2">
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      <widget class="QCheckBox" name="m_checkOpen">
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       <property name="text">
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        <string>完成后打开</string>
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       </property>
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      </widget>
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     </item>
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    </layout>
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   </item>
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   <item>
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    <spacer name="m_spacerDown">
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     <property name="orientation">
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      <enum>Qt::Vertical</enum>
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     </property>
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     <property name="sizeHint" stdset="0">
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      <size>
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       <width>20</width>
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       <height>0</height>
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      </size>
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     </property>
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    </spacer>
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   </item>
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  </layout>
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 </widget>
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 <resources/>
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 <connections/>
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</ui>

105.2.3 实现功能

C:\Users\Minwei\Projects\Qt\Downloader\downloaderdialog.h：


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#ifndef DOWNLOADERDIALOG_H
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#define DOWNLOADERDIALOG_H
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#include <QDialog>
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#include <QNetworkAccessManager>
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#include <QNetworkReply>
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#include <QFile>
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QT_BEGIN_NAMESPACE
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namespace Ui { class DownloaderDialog; }
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QT_END_NAMESPACE
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class DownloaderDialog : public QDialog
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{
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    Q_OBJECT
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public:
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    DownloaderDialog(QWidget *parent = nullptr);
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    ~DownloaderDialog();
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private slots:
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    void on_m_btnDownload_clicked();
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    void on_m_btnDefault_clicked();
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    void on_m_reply_downloadProgress(
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        qint64 bytesReceived, qint64 bytesTotal);
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    void on_m_reply_readyRead();
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    void on_m_reply_finished();
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private:
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    Ui::DownloaderDialog *ui;
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    QNetworkAccessManager* m_access;
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    QNetworkReply* m_reply;
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    QFile* m_file;
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};
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#endif // DOWNLOADERDIALOG_H

C:\Users\Minwei\Projects\Qt\Downloader\downloaderdialog.cpp：


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#include <QMessageBox>
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#include <QDir>
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#include <QDesktopServices>
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#include <QThread>
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#include "downloaderdialog.h"
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#include "ui_downloaderdialog.h"
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DownloaderDialog::DownloaderDialog(QWidget *parent)
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    : QDialog(parent)
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    , ui(new Ui::DownloaderDialog)
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    , m_access(new QNetworkAccessManager(this))
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    , m_reply(Q_NULLPTR)
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    , m_file(Q_NULLPTR)
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{
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    ui->setupUi(this);
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    on_m_btnDefault_clicked();
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}
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DownloaderDialog::~DownloaderDialog()
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{
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    delete ui;
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}
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void DownloaderDialog::on_m_btnDownload_clicked()
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{
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    QUrl url = QUrl::fromUserInput(ui->m_editUrl->text().trimmed());
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    if(!url.isValid())
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    {
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        QMessageBox::critical(this, "URL错误", url.errorString());
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        return;
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    }
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    m_file = new QFile(ui->m_editPath->text().trimmed() + "/" + url.fileName());
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    if(!m_file->open(QIODevice::WriteOnly))
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    {
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        QMessageBox::critical(this, "文件错误",
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            QString("打开“%1”文件失败！").arg(m_file->fileName()));
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        return;
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    }
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    m_reply = m_access->get(QNetworkRequest(url));
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    connect(m_reply, SIGNAL(downloadProgress(qint64, qint64)),
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        this, SLOT(on_m_reply_downloadProgress(qint64,qint64)));
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    connect(m_reply, SIGNAL(readyRead()),
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        this, SLOT(on_m_reply_readyRead()));
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    connect(m_reply, SIGNAL(finished()),
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        this, SLOT(on_m_reply_finished()));
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    ui->m_btnDownload->setEnabled(false);
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}
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void DownloaderDialog::on_m_btnDefault_clicked()
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{
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    ui->m_editPath->setText(QDir::currentPath());
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}
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void DownloaderDialog::on_m_reply_downloadProgress(
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    qint64 bytesReceived, qint64 bytesTotal)
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{
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    ui->m_progressBar->setMaximum(bytesTotal);
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    ui->m_progressBar->setValue(bytesReceived);
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}
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void DownloaderDialog::on_m_reply_readyRead()
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{
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    m_file->write(m_reply->readAll());
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}
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void DownloaderDialog::on_m_reply_finished()
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{
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    m_reply->deleteLater();
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    m_reply = Q_NULLPTR;
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    m_file->close();
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    if (ui->m_checkOpen->isChecked())
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        QDesktopServices::openUrl(QUrl::fromLocalFile(m_file->fileName()));
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    delete m_file;
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    m_file = Q_NULLPTR;
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    QThread::sleep(1);
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    ui->m_btnDownload->setEnabled(true);
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    ui->m_progressBar->setValue(0);
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}

105.2.4 测试验证

运行效果如图所示：