Qt 学习笔记 调试日志文件记录

官方文档：

<QtGlobal> - Global Qt Declarations | Qt Core 5.15.8

<QtGlobal> - Global Qt Declarations | Qt Core 6.2.4

#include <qapplication.h>
#include <stdio.h>
#include <stdlib.h>

void myMessageOutput(QtMsgType type, const QMessageLogContext &context, const QString &msg)
{
    QByteArray localMsg = msg.toLocal8Bit();
    const char *file = context.file ? context.file : "";
    const char *function = context.function ? context.function : "";
    switch (type) {
    case QtDebugMsg:
        fprintf(stderr, "Debug: %s (%s:%u, %s)\n", localMsg.constData(), file, context.line, function);
        break;
    case QtInfoMsg:
        fprintf(stderr, "Info: %s (%s:%u, %s)\n", localMsg.constData(), file, context.line, function);
        break;
    case QtWarningMsg:
        fprintf(stderr, "Warning: %s (%s:%u, %s)\n", localMsg.constData(), file, context.line, function);
        break;
    case QtCriticalMsg:
        fprintf(stderr, "Critical: %s (%s:%u, %s)\n", localMsg.constData(), file, context.line, function);
        break;
    case QtFatalMsg:
        fprintf(stderr, "Fatal: %s (%s:%u, %s)\n", localMsg.constData(), file, context.line, function);
        break;
    }
}

int main(int argc, char **argv)
{
    qInstallMessageHandler(myMessageOutput);
    QApplication app(argc, argv);
    ...
    return app.exec();
}

稍微改造下，保存到文件中

#include "mainwindow.h"

#include <QApplication>
#include <QLocale>
#include <QTranslator>

#include <QDateTime>
#include <QDir>
#include <QFile>
#include <QMutex>
#include <QTextStream>

QtMessageHandler g_DefaultHandler = nullptr;

void WriteLog(const QString foldername, const QString &msg)
{
    static QMutex mutex;
    QMutexLocker lock(&mutex);

    QString path=QDir::currentPath()+"/Log/"+foldername+"/"+QDateTime::currentDateTime().toString("yyyyMM");
    //判断路径是否存在
    QDir dir(path);
    if(dir.exists()==false)
    {
        //不存在，创建
        dir.mkpath(path);
    }

    int i=1;
    QString filename =path+"/log_"+QDateTime::currentDateTime().toString("dd")+ "_"+QString::number(i).rightJustified(3, '0') + ".txt";

    while(true)
    {
        QFileInfo fi(filename);
        if(fi.exists())
        {
            //文件过长
            if(fi.size()>1024*10)
            {
                i++;
                filename =path+"/log_"+QDateTime::currentDateTime().toString("dd")+ "_"+QString::number(i).rightJustified(3, '0') + ".txt";
                continue;
            }
            else
                break;
        }
        else
            break;

    }


    //写入文件
    QFile file(filename);
    file.open(QIODevice::WriteOnly | QIODevice::Append);
    QTextStream text_stream(&file);
    text_stream << msg;
    file.flush();
    file.close();

}


void myMessageOutput(QtMsgType type, const QMessageLogContext &context, const QString &msg)
{

    QString file = context.file ? context.file : "";
    QString function = context.function ? context.function : "";

    QString text;

    switch (type) {
    case QtDebugMsg:
        text =QString("【%1】Debug %2\r\n")
                .arg(QDateTime::currentDateTime().toString("yyyy-MM-dd hh:mm:ss")
                     ,msg);
        WriteLog("Info",text);
        break;
    case QtInfoMsg:
        text =QString("【%1】Info %2 \r\n")
                .arg(QDateTime::currentDateTime().toString("yyyy-MM-dd hh:mm:ss")
                     ,msg);
         WriteLog("Info",text);
        break;
    case QtWarningMsg:
        text =QString("【%1】Warning %2 %3 %4 \r\n%5\r\n")
                .arg(QDateTime::currentDateTime().toString("yyyy-MM-dd hh:mm:ss")
                     ,file,function, QString::number(context.line)
                     ,msg);
         WriteLog("Error",text);
        break;
    case QtCriticalMsg:
        text =QString("【%1】Critical %2 %3 %4 \r\n%5\r\n")
                .arg(QDateTime::currentDateTime().toString("yyyy-MM-dd hh:mm:ss")
                     ,file,function, QString::number(context.line)
                     ,msg);
         WriteLog("Error",text);
        break;
    case QtFatalMsg:
        text =QString("【%1】Fatal %2 %3 %4 \r\n%5\r\n")
                .arg(QDateTime::currentDateTime().toString("yyyy-MM-dd hh:mm:ss")
                     ,file,function, QString::number(context.line)
                     ,msg);
        WriteLog("Error",text);

        break;
    }




    //用系统原来的函数完成原来的功能. 比如输出到调试窗
    if(g_DefaultHandler)
    {
        g_DefaultHandler(type,context,msg);
    }


}




int main(int argc, char *argv[])
{
    //注册MessageHandler

    g_DefaultHandler = qInstallMessageHandler(myMessageOutput);

    QApplication a(argc, argv);

    qDebug("This is a debug message");
    //qInfo("This is a info message");
    //qWarning("This is a warning message");
    //qCritical("This is a critical message");
    //qFatal("This is a fatal message");


    QTranslator translator;
    const QStringList uiLanguages = QLocale::system().uiLanguages();
    for (const QString &locale : uiLanguages) {
        const QString baseName = "HMI_" + QLocale(locale).name();
        if (translator.load(":/i18n/" + baseName)) {
            a.installTranslator(&translator);
            break;
        }
    }
    MainWindow w;
    w.show();
    return a.exec();
}