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基于Qt实现日志打印系统

作者：但行技术

这篇文章主要为大家详细介绍了如何利用Qt开发一个日志打印系统,可以实现打印日志按日期、大小保存,过期删除,窗口实时显示日志,网络传输日志远程调试,需要的可以参考下

Qt 打印日志系统，实现打印日志保存，窗口显示日志，网络传输日志

一套成熟的系统往往都有相应的日志系统，以便调试查看

Qt的打印信息默认处理程序将消息打印到X11下的标准输出或Windows下的调试器，其实我们可以自己处理相关打印信息，可以选择保存下来、或者界面显示，网络传输等等，qInstallMessageHandler(QtMessageHandler handler)可以帮助我们快速实现我们的日志系统

实现方法也简单，下面是帮助文档里面为我们提供的日志

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

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

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

下面稍微改造，符合我们实际使用的三种日志形式，有使用到c++11 lambda表达式方式安装，看不惯可以按例子编写，都一样的

 enum HandlerFlag
    {
        eSave   = 0x0001,
        eNet    = 0x0002,
        eNewLog = 0x0004,
    };
    Q_DECLARE_FLAGS(HandlerFlags, HandlerFlag)

列出主要实现代码

Q_DECLARE_OPERATORS_FOR_FLAGS(QLog::HandlerFlags)

void QLog::handler(HandlerFlags flags)
{
    {
        if(d->m_flags == flags){
            return;
        }
        QMutexLocker locker(&(d->m_handlermutex));
        qInstallMessageHandler(nullptr);
        d->m_flags = flags;
        if(!d->m_flags.testFlag(eNet)){
            if(d->mp_toNet){
                d->mp_toNet->deleteLater();
                d->mp_toNet = nullptr;
            }
            if(d->mp_netThread){
                d->mp_netThread->quit();
                d->mp_netThread->wait();
                d->mp_netThread->deleteLater();
                d->mp_netThread = nullptr;
            }
        }
        if(!d->m_flags.testFlag(eSave)){
            if (d->m_file.isOpen()) {
                d->m_file.close();
            }
            d->m_fileName.clear();
        }
        if(!d->m_flags){
            return;
        }
    }

    qInstallMessageHandler(
                [](QtMsgType type, const QMessageLogContext &context, const QString &msg)
    {
        Q_UNUSED(context)
        QLogPrivate* d = QLog::instance()->d;
        QMutexLocker locker(&(d->m_handlermutex));
        if(!d->m_flags){
            return;
        }
        QString content;
        switch (type) {
        case QtDebugMsg:
            content = QString("%1").arg(msg);
            break;
        case QtWarningMsg:
            content = QString("%1").arg(msg);
            break;
        case QtCriticalMsg:
            content = QString("%1").arg(msg);
            break;
        case QtFatalMsg:
            content = QString("%1").arg(msg);
            break;
        case QtInfoMsg:
            content = QString("%1").arg(msg);
            break;
        }

        if(d->m_flags.testFlag(eSave)){

            QString fileName = QString("%1/%2_log_%3.txt").arg(d->m_path).arg(d->m_appname).arg(QDate::currentDate().toString("yyyy-MM-dd"));
            if (d->m_fileName != fileName) {
                d->m_fileName = fileName;
                if (d->m_file.isOpen()) {
                    d->m_file.close();
                }
                QLog::instance()->autoDeleteLog();
                d->m_file.setFileName(fileName);
                d->m_file.open(QIODevice::WriteOnly | QIODevice::Append | QFile::Text);
            }

            QTextStream logStream(&(d->m_file));
            logStream << content << "\n";
            if(d->m_file.size() > d->m_maxLogsize){
                QString fileName = QString("%1/%2_log_%3.txt").arg(d->m_path).arg(d->m_appname).arg(QDateTime::currentDateTime().toString("yyyy-MM-dd-hhmmss"));
                d->m_file.rename(fileName);
                d->m_file.close();
                d->m_fileName.clear();
            }
        }

        if(d->m_flags.testFlag(eNet)){
            if(nullptr == d->mp_toNet){
                QLog::instance()->createLogNet();
            }
            QLog::instance()->toNet(content);
        }

        if(d->m_flags.testFlag(eNewLog)){
            QLog::instance()->newLog(content);
        }

    });
}

简要说明下其中的部分代码

日志安装，使用到c++11 lambda表达式方式安装，看不惯可以按例子编写，都一样的

 qInstallMessageHandler(
                [](QtMsgType type, const QMessageLogContext &context, const QString &msg)
    {
    });

文件保存：

1.每次又新消息都会进入我们大安装函数中来，我们可以选择是否保存到文件当中去

2.在每次保存之前先判断下当前的文件名是否为当前日期，不是的话关闭旧的文件句柄，在按当前日期打开新的文件

3.如果文件大小大于最大值，比如1000M的大小（file.size() > d->m_maxLogsize），则重名当前文件，再打开一个新文件，防止日志文件太大

QString fileName = QString("%1/%2_log_%3.txt").arg(d->m_path).arg(d->m_appname).arg(QDate::currentDate().toString("yyyy-MM-dd"));
            if (d->m_fileName != fileName) {
                d->m_fileName = fileName;
                if (d->m_file.isOpen()) {
                    d->m_file.close();
                }
                QLog::instance()->autoDeleteLog();
                d->m_file.setFileName(fileName);
                d->m_file.open(QIODevice::WriteOnly | QIODevice::Append | QFile::Text);
            }

            QTextStream logStream(&(d->m_file));
            logStream << content << "\n";
            if(d->m_file.size() > d->m_maxLogsize){
                QString fileName = QString("%1/%2_log_%3.txt").arg(d->m_path).arg(d->m_appname).arg(QDateTime::currentDateTime().toString("yyyy-MM-dd-hhmmss"));
                d->m_file.rename(fileName);
                d->m_file.close();
                d->m_fileName.clear();
            }

过期删除，比如大于d->m_saveday （30天）的就给他删掉

void QLog::autoDeleteLog()
{
    qint64 var = d->m_saveday * (-1);
    QDateTime deleteday = QDateTime::currentDateTime().addDays(var);
    QDir dir(d->m_path);
    QStringList filters;
    filters<<"*.txt";
    dir.setNameFilters(filters);

    QFileInfoList  filelst = dir.entryInfoList();
    if( filelst.count()< d->m_saveday){
        return;
    }

    foreach (QFileInfo mItem, filelst)
    {
        if(mItem.fileName().contains(d->m_appname) && mItem.created() <= deleteday ){
            QFile::remove(mItem.absoluteFilePath());
        }
    }
}

网络传输，首先定义日志服务器

class QLogToNet:public QObject
{
    Q_OBJECT
private:
    QLogToNet(quint16 port,QObject* parent = nullptr);
    ~QLogToNet();
public slots:
    void slot_toNet(QString log);
private:
    class QLogToNetPrivate;
    QLogToNetPrivate* const d;
    friend class QLog;
};

class QLogToNet::QLogToNetPrivate
{
public:
    QMutex             m_mutex;
    QTcpServer*        mp_server;
    QList<QTcpSocket*> m_lstTcpSocket;
};

QLogToNet::QLogToNet(quint16 port, QObject *parent)
    :QObject(parent),d(new QLogToNetPrivate())
{
    d->mp_server = new QTcpServer(this);
    connect(d->mp_server,&QTcpServer::newConnection,this,[=](){
        QMutexLocker locker(&d->m_mutex);
        while (d->mp_server->hasPendingConnections()) {
            QTcpSocket* pTcpSocket = d->mp_server->nextPendingConnection();
            if(pTcpSocket){
                connect(pTcpSocket,&QTcpSocket::disconnected,this,[=]()
                {
                    QMutexLocker locker(&d->m_mutex);
                    QTcpSocket* pTcpSocket = qobject_cast<QTcpSocket*>(sender());
                    if(pTcpSocket){
                        d->m_lstTcpSocket.removeAll(pTcpSocket);
                        pTcpSocket->deleteLater();
                    }
                });
                d->m_lstTcpSocket<<pTcpSocket;
            }
        }
    });
    d->mp_server->listen(QHostAddress::AnyIPv4,port);
}

QLogToNet::~QLogToNet()
{
    if(d->mp_server->isListening()){
        d->mp_server->close();
    }
    delete d;
}

void QLogToNet::slot_toNet(QString log)
{
    QMutexLocker locker(&d->m_mutex);
    foreach (QTcpSocket* pTcpSocket ,d->m_lstTcpSocket) {
        pTcpSocket->write(log.toUtf8());
        pTcpSocket->flush();
    }
}

然后使用该日志服务器，为了性能，顺便移动到线程中去了

void QLog::createLogNet()
{
    if(nullptr == d->mp_toNet){
        d->mp_toNet = new QLogToNet(d->m_netPort,nullptr);
        connect(this,&QLog::sig_toNet,d->mp_toNet,&QLogToNet::slot_toNet);
        d->mp_netThread = new QThread(this);
        d->mp_toNet->moveToThread(d->mp_netThread);
        d->mp_netThread->start();
    }
}

则在有新消息时，我们就可以发射一个信号出去了

void QLog::toNet(QString log)
{
    emit sig_toNet(log);
}

日志服务器怎么用呢，你可以随便找个TCP工具连上你的日志服务器的IP和端口，这样你就可以远程调试查看了，如果系统在外地或者比较恶劣的环境，那调试就真是美滋滋方便多了，而且还可以多人查看呢，是不是很美好，愿意的话还可以稍微改下服务端接收一些调试命令，比如打印一些内存信息返回回来，方便调试。

窗口显示，我们定义一个显示控件QTextEdit，和newlog相连，每次有新消息直接append就可以了

connect(QLog::instance(),&QLog::sig_newLog,ui->textEdit,&QTextEdit::append);

在QTextEdit上模糊收索消息，主要用到QSyntaxHighlighter

#ifndef MARKDOWNHIGHLIGHTER_H
#define MARKDOWNHIGHLIGHTER_H

#include <QSyntaxHighlighter>
#include <QTextEdit>
#include <QVector>

class MarkdownHighlighter : public QSyntaxHighlighter
{
    Q_OBJECT
public:
    MarkdownHighlighter(QTextEdit *parent = 0);
    void highlightBlock(const QString &text);
    void SetColorText(const QString &str, const QColor &color);
    void clearRules();
    int markCount() const;
    void setMarkCount(int markCount);
private:
    struct HighlightingRule
    {
        QRegExp pattern;
        QTextCharFormat format;
    };
    QVector<HighlightingRule> m_highlightingRules;
};

#endif // MARKDOWNHIGHLIGHTER_H

实现

#include "markdownhighlighter.h"

MarkdownHighlighter::MarkdownHighlighter(QTextEdit *parent)
    :QSyntaxHighlighter(parent)
{
    this->setDocument(parent->document());
}

void MarkdownHighlighter::highlightBlock(const QString &text)
{
    foreach (HighlightingRule rule, m_highlightingRules)
    {
        QRegExp expression(rule.pattern);
        int index = text.indexOf(expression);
        while (index >= 0)
        {
            int length = expression.matchedLength();
            setFormat(index, length, rule.format);
            index = text.indexOf(expression, index + length);
        }
    }
}

void MarkdownHighlighter::SetColorText(const QString &str, const QColor &color)
{
    HighlightingRule rule;
    rule.pattern = QRegExp(str);
    QTextCharFormat format;
    format.setForeground(color);
    rule.format = format;
    m_highlightingRules.append(rule);
}

void MarkdownHighlighter::clearRules()
{
    m_highlightingRules.clear();
}

怎么用这个搜索类呢，我们可以在每次文字改变时，更新下搜索

void LogWidget::on_le_find_textChanged(const QString &)
{
    QString str = ui->le_find->text();
    if(str.isEmpty()){
        mp_findMark->clearRules();
        mp_findMark->rehighlight();
        return;
    }
    mp_findMark->clearRules();
    mp_findMark->SetColorText(str,Qt::red);
    mp_findMark->rehighlight();
}

罗里吧嗦了一堆，主要时利用qInstallMessageHandler(QtMessageHandler handler)来处理qt的打印信息，下面分享下一些比较常用的打印格式

#define LOG_DEBUG qDebug()    << qPrintable(QString("[%1 %2 %3 %4]:").arg(QDateTime::currentDateTime().toString("yyyy-MM-dd HH:mm:ss")).arg(__FILE__).arg(__FUNCTION__).arg(__LINE__))
#define LOG_INFO  qInfo()     << qPrintable(QString("[%1]:").arg(QDateTime::currentDateTime().toString("yyyy-MM-dd HH:mm:ss")))
#define LOG_WARN  qWarning()  << qPrintable(QString("[%1 %2 %3 %4]:").arg(QDateTime::currentDateTime().toString("yyyy-MM-dd HH:mm:ss")).arg(__FILE__).arg(__FUNCTION__).arg(__LINE__))
#define LOG_CRIT  qCritical() << qPrintable(QString("[%1 %2 %3 %4]:").arg(QDateTime::currentDateTime().toString("yyyy-MM-dd HH:mm:ss")).arg(__FILE__).arg(__FUNCTION__).arg(__LINE__))

以上就是基于Qt实现日志打印系统的详细内容，更多关于Qt打印日志的资料请关注脚本之家其它相关文章！

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