C/C++ Qt监控文件状态变化方式

#ifndef FILESYSTEM_H
#define FILESYSTEM_H
#include <QObject>
#include <QMap>
#include <QFileSystemWatcher>

class FileSystemWatcher : public QObject
{
    Q_OBJECT

public:
    static void addWatchPath(QString path);

public slots:
    void directoryUpdated(const QString &path);  // 目录更新时调用，path是监控的路径
    void fileUpdated(const QString &path);   // 文件被修改时调用，path是监控的路径

private:
    explicit FileSystemWatcher(QObject *parent = 0);

private:
    static FileSystemWatcher *m_pInstance; // 单例
    QFileSystemWatcher *m_pSystemWatcher;  // QFileSystemWatcher变量
    QMap<QString, QStringList> m_currentContentsMap; // 当前每个监控的内容目录列表

};
#endif // FILESYSTEM_H

#include <QDir>
#include <QFileInfo>
#include <qDebug>
#include "filesystem.h"

FileSystemWatcher* FileSystemWatcher::m_pInstance = NULL;
FileSystemWatcher::FileSystemWatcher(QObject *parent)
    : QObject(parent)
{

}

// 监控文件或目录
void FileSystemWatcher::addWatchPath(QString path)
{
    qDebug() << QString("Add to watch: %1").arg(path);

    if (m_pInstance == NULL)
    {
        m_pInstance = new FileSystemWatcher();
        m_pInstance->m_pSystemWatcher = new QFileSystemWatcher();

        // 连接QFileSystemWatcher的directoryChanged和fileChanged信号到相应的槽
        connect(m_pInstance->m_pSystemWatcher, SIGNAL(directoryChanged(QString)), m_pInstance, SLOT(directoryUpdated(QString)));
        connect(m_pInstance->m_pSystemWatcher, SIGNAL(fileChanged(QString)), m_pInstance, SLOT(fileUpdated(QString)));
    }

    // 添加监控路径
    m_pInstance->m_pSystemWatcher->addPath(path);

    // 如果添加路径是一个目录，保存当前内容列表
    QFileInfo file(path);
    if (file.isDir())
    {
        const QDir dirw(path);
        m_pInstance->m_currentContentsMap[path] = dirw.entryList(QDir::NoDotAndDotDot | QDir::AllDirs | QDir::Files, QDir::DirsFirst);
    }
}

// 只要任何监控的目录更新(添加、删除、重命名)，就会调用。
void FileSystemWatcher::directoryUpdated(const QString &path)
{
    qDebug() << QString("Directory updated: %1").arg(path);

    // 比较最新的内容和保存的内容找出区别(变化)
    QStringList currEntryList = m_currentContentsMap[path];
    const QDir dir(path);

    QStringList newEntryList = dir.entryList(QDir::NoDotAndDotDot  | QDir::AllDirs | QDir::Files, QDir::DirsFirst);

    QSet<QString> newDirSet = QSet<QString>::fromList(newEntryList);
    QSet<QString> currentDirSet = QSet<QString>::fromList(currEntryList);

    // 添加了文件
    QSet<QString> newFiles = newDirSet - currentDirSet;
    QStringList newFile = newFiles.toList();

    // 文件已被移除
    QSet<QString> deletedFiles = currentDirSet - newDirSet;
    QStringList deleteFile = deletedFiles.toList();

    // 更新当前设置
    m_currentContentsMap[path] = newEntryList;

    if (!newFile.isEmpty() && !deleteFile.isEmpty())
    {
        // 文件/目录重命名
        if ((newFile.count() == 1) && (deleteFile.count() == 1))
        {
            qDebug() << QString("File Renamed from %1 to %2").arg(deleteFile.first()).arg(newFile.first());
        }
    }
    else
    {
        // 添加新文件/目录至Dir
        if (!newFile.isEmpty())
        {
            qDebug() << "New Files/Dirs added: " << newFile;

            foreach (QString file, newFile)
            {
                // 处理操作每个新文件....
            }
        }

        // 从Dir中删除文件/目录
        if (!deleteFile.isEmpty())
        {
            qDebug() << "Files/Dirs deleted: " << deleteFile;

            foreach(QString file, deleteFile)
            {
                // 处理操作每个被删除的文件....
            }
        }
    }
}

// 文件修改时调用
void FileSystemWatcher::fileUpdated(const QString &path)
{
    QFileInfo file(path);
    QString strPath = file.absolutePath();
    QString strName = file.fileName();

    qDebug() << QString("The file %1 at path %2 is updated").arg(strName).arg(strPath);
}

FileSystemWatcher::addWatchPath("c://test");

#include <QCoreApplication>
#include "filesystem.h"

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    FileSystemWatcher::addWatchPath("c://test");

    return a.exec();
}