qt日志实现-白红宇

qt的日志有四个级别：

qDebug：调试信息

qWarning：警告信息

qCritical：严重错误

qFatal：致命错误

可以通过<QtGlobal>下的

void qCritical ( const char * msg, ... );

void qDebug ( const char * msg, ... );

void qFatal ( const char * msg, ... );

void qWarning ( const char * msg, ... );

或include <QtDebug>时,采用更便捷输出

qDebug()<<"debug";

qWarning()<<"warning";

qCritical()<<"critical";

在程序调试中这样的line printf输出没问题，如果app被部署后需要将这些输出的日志输出到日志文件中，需通过

QtMsgHandler qInstallMsgHandler ( QtMsgHandler handler )设置输出，如果想取消输出可通过qInstallMsgHandler(0)设置

qt日志输出示例：

void logMsgHandler(QtMsgType type, const char *msg)

{

QString strLog;

switch (type) {

case QtDebugMsg:

strLog = QString(QDateTime::currentDateTime().toString("yyyy-MM-dd hh:mm:ss ")+"[Debug] %1").arg(QObject::tr(msg));

break;

case QtWarningMsg:

strLog = QString(QDateTime::currentDateTime().toString("yyyy-MM-dd hh:mm:ss ")+"[Warn] %1").arg(QObject::tr(msg));

break;

case QtCriticalMsg:

strLog = QString(QDateTime::currentDateTime().toString("yyyy-MM-dd hh:mm:ss ")+"[Critical] %1").arg(QObject::tr(msg));

break;

case QtFatalMsg:

strLog = QString(QDateTime::currentDateTime().toString("yyyy-MM-dd hh:mm:ss ")+"[Fatal] %1").arg(QObject::tr(msg));

// abort();

default:

break;

}

//更复杂的写入文件按实际需求设置

QFile outFile("debug.log");

outFile.open(QIODevice::WriteOnly | QIODevice::Append);

/**< the max size of log.txt.*/

if(outFile.size()>10000)

{

outFile.close();

//清空旧日志

outFile.open(QIODevice::WriteOnly | QIODevice::Append | QIODevice::Truncate);

outFile.close();

outFile.open(QIODevice::WriteOnly | QIODevice::Append);

}

QTextStream ts(&outFile);

ts << strLog << endl;

};

#include <QDebug>

int main(int argc, char **argv)

{

qInstallMsgHandler(myMessageOutput);

QApplication app(argc, argv);

//打印日志到文件中

qDebug("debug");

qWarning("warning");

qCritical("critical");

qFatal("fatal");

qDebug()<<"debug_";

qWarning()<<"warning_";

qCritical()<<"critical_";

return app.exec();

}