Qt重定向qDebug，实现日志系统（QtDebugMsg、QtInfoMsg、QtWarningMsg、QtCriticalMsg、QtFatalMsg）

深藏阁楼爱情的钟 2022-03-12 09:18 426阅读 0赞

## 原理： ##

重定向qDebug、qInfo、qWarning、qCritical、qFatal等宏，输出到txt文件。如果需要输出到Qt控件上，则需要使用Qt提供的反射机制。

## 效果图： ##

![在这里插入图片描述][20190305171822633.gif]

## 目录结构如下： ##

![在这里插入图片描述][2019030517084217.png]

## 重点关注： ##

qInstallMessageHandler（）  
QMetaObject::invokeMethod(）

## 源码： ##

MsgHandlerWapper.h：

#ifndef MSGHANDLERWAPPER_H
    #define MSGHANDLERWAPPER_H
    
    #include <QObject>
    
    class MsgHandlerWapper : public QObject
    {
        Q_OBJECT
    public:
        static MsgHandlerWapper * instance();
    
    signals:
        void message(QtMsgType type, const QMessageLogContext &context,const QString &msg);
    
    private:
        MsgHandlerWapper();
        static MsgHandlerWapper * m_instance;
    };
    
    #endif // MSGHANDLERWAPPER_H

MsgHandlerWapper.cpp：

#include "msghandlerwapper.h"
    #include <QtCore/QMetaType>
    #include <QtCore/QMutex>
    #include <QtCore/QMutexLocker>
    #include <QtCore/QCoreApplication>
    #include <QString>
    
    MsgHandlerWapper * MsgHandlerWapper::m_instance = nullptr;
    
    void myMessageOutput(QtMsgType type, const QMessageLogContext &context, const QString &msg)
    {
        QMetaObject::invokeMethod(MsgHandlerWapper::instance(), "message" , Q_ARG(QtMsgType, type) ,Q_ARG(QMessageLogContext , context) ,  Q_ARG(QString, QString(msg)));
    }
    
    MsgHandlerWapper * MsgHandlerWapper::instance()
    {
        static QMutex mutex;
        if (!m_instance)
        {
            QMutexLocker locker(&mutex);
            if (!m_instance)
                m_instance = new MsgHandlerWapper;
        }
    
        return m_instance;
    }
    
    MsgHandlerWapper::MsgHandlerWapper():QObject(qApp)
    {
        qRegisterMetaType<QtMsgType>("QtMsgType");
        qInstallMessageHandler(myMessageOutput);
    }

LogTextEdit.h:

#ifndef LOGTEXTEDIT_H
    #define LOGTEXTEDIT_H
    #include <QPlainTextEdit>
    #include <QTextStream>
    #include <QDateTime>
    #include "msghandlerwapper.h"
    #include <QDebug>
    
    class LogTextEdit : public QPlainTextEdit
    {
        Q_OBJECT
    
    private:
        QTextStream gOutStream;
        QFile logFile;
    
    public:
        explicit LogTextEdit(QWidget * parent = nullptr) :QPlainTextEdit(parent)
        {
            connect(MsgHandlerWapper::instance(), SIGNAL(message(QtMsgType,QMessageLogContext ,QString)), SLOT(outputMessage(QtMsgType,QMessageLogContext ,QString)));
            openLogFile();
        }
    
        ~LogTextEdit()
        {
            logFile.flush();
            logFile.close();
            gOutStream.flush();
        }
    public slots:
        void outputMessage(QtMsgType type, const QMessageLogContext &context ,const QString &msg)
        {
            QByteArray localMsg = msg.toLocal8Bit();
            QString text;
            QString htmlText;
            switch (type)
            {
            case QtDebugMsg:
                text = QString::fromLocal8Bit("Debug: %1 (%2:%3, %4)\n").arg(QString::fromLocal8Bit(localMsg.constData())).arg(context.file).arg(context.line).arg(context.function);
                htmlText = formatHtml(text , "green");
                break;
            case QtInfoMsg:
                text = QString::fromLocal8Bit("Info: %1 (%2:%3, %4)\n").arg(QString::fromLocal8Bit(localMsg.constData())).arg(context.file).arg(context.line).arg(context.function);
                htmlText = formatHtml(text , "green");
                break;
            case QtWarningMsg:
                text = QString::fromLocal8Bit("Warning: %1 (%2:%3, %4)\n").arg(QString::fromLocal8Bit(localMsg.constData())).arg(context.file).arg(context.line).arg(context.function);
                htmlText = formatHtml(text , "rgb(255, 170, 0)");
                break;
            case QtCriticalMsg:
                text = QString::fromLocal8Bit("Critical: %1 (%2:%3, %4)\n").arg(QString::fromLocal8Bit(localMsg.constData())).arg(context.file).arg(context.line).arg(context.function);
                htmlText = formatHtml(text , "red");
                break;
            case QtFatalMsg:
                text = QString::fromLocal8Bit("Fatal: %1 (%2:%3, %4)\n").arg(QString::fromLocal8Bit(localMsg.constData())).arg(context.file).arg(context.line).arg(context.function);
                htmlText = formatHtml(text , "red");
                break;
            default:
                text = QString::fromLocal8Bit("Default: %1 (%2:%3, %4)\n").arg(QString::fromLocal8Bit(localMsg.constData())).arg(context.file).arg(context.line).arg(context.function);
                htmlText = formatHtml(text , "black");
            }
    
            gOutStream << QDateTime::currentDateTime().toString("[yyyy-MM-dd hh.mm.ss]\t") + text; //输出到txt文件
            gOutStream .flush(); //刷新缓冲区
            appendHtml(htmlText);
        }
    
    private:
        void openLogFile()
        {
            logFile.setFileName("./Df_Soft_Log.txt");
            if(!logFile.open(QIODevice::WriteOnly | QIODevice::Text | QIODevice::Append))
            {
                //
            }
            else
            {
                gOutStream.setDevice(&logFile);
            }
        }
    
        const QString formatHtml(const QString &qText , QString color)
        {
            return QString("<font style='font-size:16px; background-color:white; color:%2;'> %1 </font>").arg(qText).arg(color);
        }
    };
    
    #endif // LOGTEXTEDIT_H

## 源码下载 ##

地址：[https://download.csdn.net/download/rl529014/10998010][https_download.csdn.net_download_rl529014_10998010]

同类文章链接：[https://blog.csdn.net/rl529014/article/details/81462079][https_blog.csdn.net_rl529014_article_details_81462079]

[20190305171822633.gif]: /images/20220312/50b9cabc0eb24d54a9c610a28c800782.png
[2019030517084217.png]: /images/20220312/83ec3556902f4ffda8a6e96a759407c4.png
[https_download.csdn.net_download_rl529014_10998010]: https://download.csdn.net/download/rl529014/10998010
[https_blog.csdn.net_rl529014_article_details_81462079]: https://blog.csdn.net/rl529014/article/details/81462079