1. 效果

• 可以显示复制文件和文件夹的进度
  
• 复制文件： bool copyFileFunc(QString _from, QString _to);
• 复制文件夹：bool copyDirectoryFiles(const QString &_from, const QString &_to);
• 举例：

	//复制文件
    copyhelper.copyFileToDir("./test.txt", "d:/copytest/dir/test1.txt");
    
    //复制文件夹
    copyhelper.copyFileToDir("./copyTest", "d:/copytest/dir/copyTest1");

2. QML代码

import QtQuick 2.15
import QtQuick.Window 2.15
import QtQuick.Controls 2.15
import QtQuick.Controls.Styles 1.4
import QtQuick.Controls 1.4

Window {
    width: 640
    height: 480
    visible: true
    title: qsTr("copy file")

    Rectangle{
        id: _progress
        width: parent.width
        height: parent.height / 2
        border.color: "blue"
        border.width: 1
        property string processv: "0"

        ProgressBar {
            id: pbar
            width: 480;
            height: 30
            minimumValue:  0
            maximumValue:  100
            value: 0
            anchors.centerIn: parent

            style: ProgressBarStyle{
                id: progressStyle

                background: Rectangle{
                    color: "lightgrey"
                    radius: 6
                }
                progress: Rectangle{
                    color: control.value === 100 ? "#b1d946" :"#4c7aff"
                    radius: 6
                }

                panel: Item{
                    //通过panel属性，可以加载  progress Text background等组件
                    //设置外边框
                    implicitWidth: 480;
                    implicitHeight: 15;

                    Loader{
                        anchors.fill:  parent;
                        sourceComponent: background;
                    }

                    Loader{
                        id: progressLoader;
                        anchors.top: parent.top;
                        anchors.left: parent.left;
                        anchors.bottom:  parent.bottom;
                        anchors.margins: 0;
                        z: 1;
                        width: currentProgress * (parent.width);
                        sourceComponent: progressStyle.progress;
                    }

                    Text{
                        color: "black"
                        text: _progress.processv
                        z: 2
                        anchors.centerIn: parent
                    }
                }
            }
        }
    }


    Button{
        width: 200
        height: 100
        anchors.top: _progress.bottom
        anchors.horizontalCenter: _progress.horizontalCenter
        anchors.topMargin: 20
        text: qsTr("开始复制")

        onClicked: {
            console.log("开始复制")
            //复制文件
            //copyhelper.copyFileToDir("./test.txt", "d:/copytest/dir/test1.txt");
            //复制文件夹
            copyhelper.copyFileToDir("./copyTest", "d:/copytest/dir/copyTest1");
        }
    }

    Connections{
        target: copyhelper

        function onQmlCopyProgress(value){
            pbar.value = value;
            _progress.processv =  value + "%";
        }
    }
}

3. main.c代码

#include <QGuiApplication>
#include <QtQml>
#include <QApplication>
#include <QQmlApplicationEngine>
#include "copyhelper.h"


int main(int argc, char *argv[])
{
#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
#endif
    QApplication app(argc, argv);

    QQmlApplicationEngine engine;

    engine.rootContext()->setContextProperty("copyhelper", new CopyHelper);

    const QUrl url(QStringLiteral("qrc:/main.qml"));
    QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
        &app, [url](QObject *obj, const QUrl &objUrl) {
            if (!obj && url == objUrl)
                QCoreApplication::exit(-1);
        }, Qt::QueuedConnection);
    engine.load(url);

    return app.exec();
}

4. .pro代码

QT += quick qml widgets core

# You can make your code fail to compile if it uses deprecated APIs.
# In order to do so, uncomment the following line.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

SOURCES += \
        copyfiles.cpp \
        copyhelper.cpp \
        main.cpp

RESOURCES += qml.qrc

# Additional import path used to resolve QML modules in Qt Creator's code model
QML_IMPORT_PATH =

# Additional import path used to resolve QML modules just for Qt Quick Designer
QML_DESIGNER_IMPORT_PATH =

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

HEADERS += \
    copyfiles.h \
    copyhelper.h

5. C++代码

• 创建两个类 CopyHelper 和 CopyFiles
• CopyFiles中是具体实现
• CopyHelper 为了实现多线程

5.1 copyfile.h

#ifndef COPYFILES_H
#define COPYFILES_H

#include <QObject>
#include <QDebug>
#include <QFile>        //文件操作
#include <QDataStream>  //数据流
#include <QThread>      //线程

class CopyFiles : public QObject
{
    Q_OBJECT
public:
    //只能显式构造
    /**
     *  QString _srcFilePath    : 源文件路径
     *  QString _dstPath        : 目标路径
     *  QObject *parent = 0     : 父对象指针，默认为空
    */
    explicit CopyFiles(QString _srcFilePath, QString _dstPath,QObject *parent = 0);

signals:
    void startCopyFile(QString, QString);   //复制文件信号
    void startCopyDir(QString, QString);    //复制文件夹信号
    void copyProcess(QString);              //复制文件进度信号

public slots:
    /**
     * @brief copyFileFunction : 复制文件信号处理槽
     * @param _from : 源文件名
     * @param _to   : 目标文件名
     * @return bool : 返回类型 成功返回true 失败返回false
    */
    bool copyFileFunc(QString _from, QString _to);

    /**
     * @brief copyDirectoryFiles : 复制文件夹
     * @param _from : 源文件夹路径
     * @param _to   : 目标文件夹路径
     * @return  : 成功返回true 失败返回false
     */
    bool copyDirectoryFiles(const QString &_from, const QString &_to);

private:
    bool m_firstRead = true;
    qint64 m_total = 0;
    qint64 m_now = 0;

private:
    void getDirSize(QString _dir, qint64* size);
    bool copyFile(QString _from, QString _to, qint64* nowSize, qint64 totalSize);
};

#endif // COPYFILES_H

5.2 copyfile.cpp

#include "copyfiles.h"
#include "qfileinfo.h"
#include <QFile>
#include <QDir>

CopyFiles::CopyFiles(QString _srcFilePath, QString _dstPath, QObject *parent)
{
    qDebug() << QThread::currentThreadId() << _srcFilePath << _dstPath;
}


bool CopyFiles::copyFileFunc(QString _from, QString _to)
{
    qint64 fileSize = 0;
    qint64 totalCopySize = 0;

    //文件夹创建
    QFileInfo fininfo(_to);
    QDir path;
    if(!path.exists(fininfo.absolutePath())){
        path.mkdir(fininfo.absolutePath());
    }

    //文件对象
    QFile tofile;
    tofile.setFileName(_to);
    QFile fromfile;
    fromfile.setFileName(_from);
    fileSize = fromfile.size();

    /* 复制文件 */
    return copyFile(_from, _to, &totalCopySize, fileSize);
}

bool CopyFiles::copyDirectoryFiles(const QString &_from, const QString &_to)
{
    QDir sourceDir(_from);
    QDir targetDir(_to);

    qDebug() << "copy form" <<_from << _to;

    /* 如果目录不存在，则创建 */
    if(!targetDir.exists()){
        if(!targetDir.mkdir(targetDir.absolutePath())){
            return false;
        }
    }

    QFileInfoList fileInfoList = sourceDir.entryInfoList();
    if(m_firstRead){
        qDebug() << "copyDirectoryFiles count:" << fileInfoList.count();

        /* 获取文件夹总大小 */
        m_total = 0;
        getDirSize(_from, &m_total);

        /* 标志位 */
        m_now = 0;
        m_firstRead = false;
        qDebug() << "copyDirectoryFiles: " << m_total << m_now;

        /* 复制完成 */
        if(m_now == m_total){
            m_firstRead = true;
        }
    }

    foreach(QFileInfo fileInfo, fileInfoList){
        if(fileInfo.fileName() == "." || fileInfo.fileName() == ".."){
            continue;
        }

        /* 当前为目录递归进行copy */
        if(fileInfo.isDir()){
            if(!copyDirectoryFiles(fileInfo.filePath(), targetDir.filePath(fileInfo.fileName()))){
                return false;
            }
        }
        /* 复制文件 */
        else{
            if(!copyFile(fileInfo.filePath(), targetDir.filePath(fileInfo.fileName()), &m_now, m_total)){
                return false;
            }
        }
    }

    return true;
}

void CopyFiles::getDirSize(QString _dir, qint64* size)
{
    QDir sourceDir(_dir);
    QFileInfoList fileInfoList = sourceDir.entryInfoList();

    /* 遍历文件夹 */
    foreach(QFileInfo fileInfo, fileInfoList){
        if(fileInfo.isFile()){
            if(fileInfo.fileName() != "." && fileInfo.fileName() != ".."){
                *size += fileInfo.size();
                qDebug() << "1-----" << fileInfo.fileName() << *size;
            }
        }else if(fileInfo.isDir()){
            /* 递归 */
            if(fileInfo.fileName() != "." && fileInfo.fileName() != ".."){
                getDirSize(fileInfo.filePath(), size);
                qDebug() << "2-----" << fileInfo.fileName() <<fileInfo.filePath();
            }
        }
    }
}

bool CopyFiles::copyFile(QString _from, QString _to, qint64* nowSize, qint64 totalSize)
{
    qDebug() << "子线程ID:" << QThread::currentThreadId();

    char * byteTemp = new char[1024*8]; //每次复制8k
    qint64 fileSize = 0;
    qint64 totalCopySize = 0;

    //文件夹创建
    QFileInfo fininfo(_to);
    QDir path;
    if(!path.exists(fininfo.absolutePath())){
        path.mkdir(fininfo.absolutePath());
    }

    //文件对象
    QFile tofile;
    tofile.setFileName(_to);
    QFile fromfile;
    fromfile.setFileName(_from);

    //文件读取判断
    if(!tofile.open(QIODevice::WriteOnly))
    {
        qDebug() << "无法打开目标文件1";
        delete[](byteTemp);
        return false;
    }
    if(!fromfile.open(QIODevice::ReadOnly)){
        qDebug() << "无法打开目标文件2";
        delete[](byteTemp);
        return false;
    }

    //文件大小
    QDataStream out(&tofile);//文件流
    out.setVersion(QDataStream::Qt_4_0);
    fileSize = fromfile.size();
    QDataStream in(&fromfile);
    in.setVersion(QDataStream::Qt_4_0);
    qDebug() << "文件总大小:" << fileSize << " / " << QString::number(totalSize);

    //循环复制文件
    while(!in.atEnd())
    {
        qint64 readSize = 0;

        //每次读取8k
        readSize = in.readRawData(byteTemp, 1024*8);    //读取复制文件到缓存并返回读取的实际大小
        out.writeRawData(byteTemp, readSize);           //写到输出流
        totalCopySize += readSize;                      //累计已复制大小
        *nowSize += readSize;
        int tmpVal = *nowSize / (double)totalSize * 100;//复制进度计算
        emit copyProcess(QString::number(tmpVal));      //发射当前复制进度
        //qDebug() << "now:" << *nowSize;
    }

    //复制完成
    if(totalCopySize == fileSize){
        tofile.setPermissions(QFile::ExeUser);//设置文件权限
        tofile.close();     //关闭文件流
        fromfile.close();   //关闭文件流
        delete[](byteTemp);
        return true;        //返回复制结果-成功
    }else{
        delete[](byteTemp);
        return false;       //返回复制结果-失败
    }
}

5.3 copyhelper.h

#ifndef COPYHELPER_H
#define COPYHELPER_H

#include <QObject>


class CopyHelper : public QObject
{
    Q_OBJECT
public:
    explicit CopyHelper(QObject *parent = 0);

public:
    /**
      * @brief copyFileToDir 复制文件到目录
      * @return QString 返回字符串
    */
    Q_INVOKABLE QString copyFileToDir(QString _from, QString _to);

signals:
    /**
     * @brief qmlCopyProgress 供qml使用的复制文件进度信号
     * @param value
     */
    void  qmlCopyProgress(QString value);

private :
    /**
     * @brief testReadFile 测试读取文件
     */
    void testReadFile();

private slots:
    /**
      * @brief reciveCopyProgress 接收文件进度槽
      */
    void reciveCopyProgress(QString);
};

#endif // COPYHELPER_H

5.4 copyhelper.cpp

#include "copyhelper.h"
#include <QDebug>
#include <QFile>
#include <QDataStream>
#include <QThread>
#include <QFileInfo>
#include "copyfiles.h"

CopyHelper::CopyHelper(QObject *parent) : QObject(parent)
{
    qDebug() << "文件复制助手线程ID:" <<QThread::currentThreadId();
}

//复制文件到目录
QString CopyHelper::copyFileToDir(QString _from, QString _to)
{
    //构造复制文件类
    CopyFiles * m_pCopyFile = new CopyFiles(_from, _to);

    //复制文件子线程
    QThread * m_pCopyFilethread =  new QThread();
    m_pCopyFile->moveToThread(m_pCopyFilethread); //子线程中执行文件复制

    //连接文件复制信号
    connect(m_pCopyFile,SIGNAL(startCopyFile(QString,QString)),m_pCopyFile,SLOT(copyFileFunc(QString,QString)));
    connect(m_pCopyFile,SIGNAL(startCopyDir(QString,QString)),m_pCopyFile,SLOT(copyDirectoryFiles(QString,QString)));
    connect(m_pCopyFile,SIGNAL(copyProcess(QString)),this,SLOT(reciveCopyProgress(QString)));

    //链接线程完成信号
    connect(m_pCopyFilethread, SIGNAL(finished()), m_pCopyFilethread, SLOT(deleteLater()));
    connect(m_pCopyFilethread, &QThread::finished, m_pCopyFilethread, &QObject::deleteLater);

    //启动复制线程
    m_pCopyFilethread->start();

    //判断文件还是文件夹
    QFileInfo fileInfo(_from);
    if(fileInfo.isDir()){
        //发射文件夹复制开始信号
        emit m_pCopyFile->startCopyDir(_from, _to);
    }else{
        //发射文件复制开始信号
        emit m_pCopyFile->startCopyFile(_from, _to);
    }

    return "复制成功";
}

//测试读取文件
void CopyHelper::testReadFile()
{
    //测试复制文件
    QString strFileName = "d:/test.rar";
    if (!QFile::exists(strFileName)){return;} //文件不存在

    QFile file(strFileName);
    if (!file.open(QFile::ReadOnly)){return;}//文件无法打开

    QDataStream in(&file);      //数据流
    int nFileSize = file.size();//文件大小
    int p = 0;                  //当前复制位置

    while (!in.atEnd()) {
        char buffer [8192];
        int readsize = 0;

        readsize = in.readRawData(buffer,8192);
        p = file.pos();
        qDebug() <<"文件总大小:"<<nFileSize<<"读取大小"<<readsize<<" 当前复制进度"<<QString::number(p);
    }
}

//接收文件进度
void CopyHelper::reciveCopyProgress(QString value)
{
    emit qmlCopyProgress(value);//发射接收文件进度
}

6. 参考

• QML复制文件并显示进度
• Qt制作有进度条的拷贝文件夹和文件的小Demo