重定向qDebug、qWarning等到某个Qt窗口部件

起源

看到 QtDev wiki 中有一篇文章QDebug 输出的浏览窗口。实现了将qDebug、qWarning等输出显示到一个窗口部件（QTextBrowser）中。看完后，个人似乎对这堆代码不太感冒，于是自己试着写写，有了下面的代码：

实现了什么?

定义了一个 MsgHandlerWapper 的类
qDebug、qWarning 等的输出会通过该类的 message 信号发送出来
如果想让某个窗口接收消息，只需要定义一个槽，然后连接到该信号。

使用举例

如果要使用一个QPlainTextEdit作为log窗口，你只需要简单定义一个槽
connect到MsgHandlerWapper实例的信号即可
#include <QPlainTextEdit>
#include "msghandlerwapper.h"
class TextEdit:public QPlainTextEdit
{
Q_OBJECT
public:
explicit TextEdit(QWidget * parent = 0)
:QPlainTextEdit(parent)
{
connect(MsgHandlerWapper::instance(),
SIGNAL(message(QtMsgType,QString)),
SLOT(outputMessage(QtMsgType,QString)));
}
public slots:
void outputMessage(QtMsgType type, const QString &msg)
{
appendPlainText(msg);
}
};

代码

msghandlerwapper.h
/*
(C) 2011 dbzhang800#gmail.com
*/
#ifndef MSGHANDLERWAPPER_H
#define MSGHANDLERWAPPER_H
#include <QtCore/QObject>

class MsgHandlerWapper:public QObject
{
Q_OBJECT
public:
static MsgHandlerWapper * instance();

signals:
void message(QtMsgType type, const QString &msg);

private:
MsgHandlerWapper();
static MsgHandlerWapper * m_instance;
};

#endif // MSGHANDLERWAPPER_Hsmsghandlerwapper.cpp
/*
(C) 2011 dbzhang800#gmail.com
*/

#include "msgwapper.h"
#include <QtCore/QMetaType>
#include <QtCore/QMutex>
#include <QtCore/QMutexLocker>
#include <QtCore/QCoreApplication>

void static msgHandlerFunction(QtMsgType type, const char *msg)
{
QMetaObject::invokeMethod(MsgHandlerWapper::instance(), "message"
, Q_ARG(QtMsgType, type)
, Q_ARG(QString, QString::fromLocal8Bit(msg)));
}

MsgHandlerWapper * MsgHandlerWapper::m_instance = 0;

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");
qInstallMsgHandler(msgHandlerFunction);
}

参考

http://developer.qt.nokia.com/wiki/Browser_for_QDebug_output
http://blog.csdn.net/dbzhang800/article/details/6449874