Qt实现记录日志文件log

概述

Qt有两种实现记录日志的方式，第一种是安装自定义的Qt消息处理程序，自动输出程序产生的调试消息、警告、关键和致命错误消息的函数；第二种是自定义一个类，可以在程序指定位置打印输出指定的内容。

第一种qInstallMessageHandler方式

自定义消息处理函数，然后安装该函数，注意此时QDebug的消息将会输出在日志文件，Qt程序调式时不再打印。
main.cpp

#include "widget.h"
#include 
#include 
#include 
#include 
#include 
#include 

void outputMessage(QtMsgType type,const QMessageLogContext &context,const QString &msg);
int main(int argc, char *argv[])
{
    qInstallMessageHandler(outputMessage);//安装消息处理程序
    QApplication a(argc, argv);
    Widget w;
    w.show();

    return a.exec();
}

void outputMessage(QtMsgType type,const QMessageLogContext &context,const QString &msg)
{
    static QMutex mutex;
    mutex.lock();
    QByteArray localMsg = msg.toLocal8Bit();
    QString text;
    switch (type)
    {
        case QtDebugMsg:
            text = QString("Debug:");
            break;
        case QtWarningMsg:
            text = QString("Warning:");
            break;
        case QtCriticalMsg:
            text = QString("Critical:");
            break;
        case QtFatalMsg:
            text = QString("Fatal:");
            break;
        default:
            text = QString("Debug:");
    }

    // 设置输出信息格式
       QString context_info = QString("File:(%1) Line:(%2)").arg(QString(context.file)).arg(context.line); // F文件L行数
       QString strDateTime = QDateTime::currentDateTime().toString("yyyy-MM-dd hh:mm:ss");
       //QString strMessage = QString("%1 %2 \t%3 \t%4").arg(text).arg(context_info).arg(strDateTime).arg(msg);
       QString strMessage = QString("%1 \t%2 \t%3").arg(text).arg(strDateTime).arg(msg);
       // 输出信息至文件中（读写、追加形式）
       QFile file(QString(QDateTime::currentDateTime().toString("yyyy-MM-dd").append("-log.txt")));
       file.open(QIODevice::ReadWrite | QIODevice::Append);
       QTextStream stream(&file);
       stream << strMessage << "\r\n";
       file.flush();
       file.close();
       // 解锁
        mutex.unlock();
}

第二种：自定义一个类，实现输出日志接口

定义一个日志类，实现输出日志到指定文件的接口，在需要输出日志的地方调用接口即可。
clog.h

#ifndef CLOG_H
#define CLOG_H

#include 

class  CLog : public QObject
{
    Q_OBJECT
public:

    /*!
     *  @brief 日志等级
     */
    enum CLOG_LEVEL
    {
        RINFO,               /*!<    提示  */
        RWARNING,            /*!<    警告  */
        RERROR               /*!<    错误  */
    };
    Q_FLAG(CLOG_LEVEL)

    struct LogConfig
    {
        bool isRecord2File;     /*!< 是否记录到文件 */
        int level;              /*!< 记录日志等级，大于等于此level的日志将被记录 */
    };

    CLog();

    void setLogLevel(const CLog::CLOG_LEVEL & level);
    CLog::CLOG_LEVEL getLogLevel(){return logLevel;}

    static bool init(CLog::LogConfig & logConfig);
    static bool createDir(QString dirPath);

    static void log(CLOG_LEVEL nLevel,const char * fileDesc,const char * functionDesc, int lineNum,const char* data, ...);

private:
    static QString getLeveDesc(CLOG_LEVEL level);

private:
    static bool isRecord2File;
    static bool isFileReady;
    static CLOG_LEVEL logLevel;
};

#ifdef Q_OS_WIN
#define FILE_SEPARATOR '\\'
#else
#define FILE_SEPARATOR '/'
#endif

#define FUNC_SEPARATOR '::'

#ifndef QT_NO_DEBUG
#define __FILENAME__ (strrchr(__FILE__, FILE_SEPARATOR) ? (strrchr(__FILE__, FILE_SEPARATOR) + 1):__FILE__)
#define __FUNNAME__ (strrchr(__FUNCTION__,FUNC_SEPARATOR)?(strrchr(__FUNCTION__, FUNC_SEPARATOR) + 1):__FUNCTION__)
#else
#define __FILENAME__ NULL
#define __FUNNAME__ NULL
#endif

#define CLOG_INFO(...)       CLog::log(CLog::RINFO,__FILENAME__,__FUNNAME__,__LINE__, __VA_ARGS__)
#define CLOG_WARNING(...)    CLog::log(CLog::RWARNING, __FILENAME__,__FUNNAME__, __LINE__,__VA_ARGS__)
#define CLOG_ERROR(...)      CLog::log(CLog::RERROR,__FILENAME__,__FUNNAME__,__LINE__,__VA_ARGS__)

#endif // CLOG_H

clog.cpp

#include "clog.h"

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

#include 

const char PATH_LogPath[] = "/../logs";
const char Suffix[] = ".log";

#define MAX_LOG_LENGH 1024

bool CLog::isFileReady = false;
bool CLog::isRecord2File = true;
CLog::CLOG_LEVEL CLog::logLevel = CLog::RINFO;           //默认是info级

QFile localFile;
QMutex mutex;

CLog::CLog()
{
}

void CLog::setLogLevel(const CLog::CLOG_LEVEL &level)
{
    logLevel = level;
}

bool CLog::init(LogConfig &logConfig)
{
    isRecord2File = logConfig.isRecord2File;
    logLevel = (CLog::CLOG_LEVEL)logConfig.level;

    QString logDir = qApp->applicationDirPath() +  QString(PATH_LogPath);
    if(createDir(logDir))
    {
        QString fileName = logDir + QDir::separator() + QDate::currentDate().toString("yyyy-MM-dd") + QString(Suffix);
        localFile.setFileName(fileName);
        if(localFile.open(QFile::WriteOnly|QFile::Append|QFile::Text))
        {
            isFileReady = true;
        }
    }
    return isFileReady;
}

bool CLog::createDir(QString dirPath)
{
    QFileInfo fileInfo(dirPath);
    if(!fileInfo.exists())
    {
        QDir tmpDir;
        return tmpDir.mkpath(dirPath);
    }

    return true;
}

void CLog::log(CLOG_LEVEL nLevel, const char *fileDesc, const char *functionDesc, int lineNum, const char* data, ...)
{
    QMutexLocker locker(&mutex);
    if(isFileReady && nLevel >= logLevel)
    {
        QString recordInfo = QString("[%1]").arg(QDateTime::currentDateTime().toString("yyyy-MM-dd hh:mm:ss:zzz"));
        recordInfo.append(getLeveDesc(nLevel));

#ifndef QT_NO_DEBUG
        recordInfo.append(QString("[%1:%2:%3]").arg(fileDesc).arg(functionDesc).arg(lineNum));
#endif
        va_list vlist;
        va_start(vlist,data);

        QByteArray byteArray;
#if defined(Q_OS_WIN)
        int recordLen = _vscprintf(data,vlist);
        byteArray.resize(recordLen);
#else
        byteArray.resize(1024);
#endif
        vsprintf(byteArray.data(),data,vlist);
        recordInfo.append(byteArray);
        va_end(vlist);

        recordInfo.append("\n");

        if(isRecord2File){
            localFile.write(recordInfo.toLocal8Bit().data(),recordInfo.toLocal8Bit().length());
            localFile.flush();
        }else{
//            qDebug()<
        }
    }
}

QString CLog::getLeveDesc(CLog::CLOG_LEVEL level)
{
#if (QT_VERSION > 0x050500)
    static QMetaEnum metaEnum = QMetaEnum::fromType<CLog::CLOG_LEVEL>();
    return QString("[%1]").arg(metaEnum.key(level));
#else
    switch(level)
    {
        case CLOG_LEVEL::INFO:
                                return "[INFO]";
        case CLOG_LEVEL::INFO:
                                return "[WARNING]";
        case CLOG_LEVEL::INFO:
                                return "[ERROR]";
    }
#endif
}

简单调用示例：

    CLog::LogConfig logConfig;
    logConfig.isRecord2File = true;
    logConfig.level = 0;
    CLog::init(logConfig);
    CLOG_INFO("df2008");

输出日志：
[2020-12-03 13:15:14:549][RINFO][widget.cpp:Widget:17]df2008