如何重定向qDebug，qWarning，qCritical等输出？

Question

我在qDebug() <<调试输出中使用了很多语句。有什么跨平台的方法可以将调试输出重定向到文件，而无需使用Shell脚本？我猜想open（）和dup2（）将在Linux中完成这项工作，但可以在Windows中与MinGW一起编译吗？

也许有Qt方法可以做到？

Answer 1

您必须使用qInstallMsgHandler函数安装消息处理程序，然后才能QTextStream将调试消息写入文件中。这是一个示例示例：#include <QtGlobal>#include <stdio.h>#include <stdlib.h>void myMessageOutput(QtMsgType type, const QMessageLogContext &context, const QString &msg){&nbsp; &nbsp; QByteArray localMsg = msg.toLocal8Bit();&nbsp; &nbsp; switch (type) {&nbsp; &nbsp; case QtDebugMsg:&nbsp; &nbsp; &nbsp; &nbsp; fprintf(stderr, "Debug: %s (%s:%u, %s)\n", localMsg.constData(), context.file, context.line, context.function);&nbsp; &nbsp; &nbsp; &nbsp; break;&nbsp; &nbsp; case QtInfoMsg:&nbsp; &nbsp; &nbsp; &nbsp; fprintf(stderr, "Info: %s (%s:%u, %s)\n", localMsg.constData(), context.file, context.line, context.function);&nbsp; &nbsp; &nbsp; &nbsp; break;&nbsp; &nbsp; case QtWarningMsg:&nbsp; &nbsp; &nbsp; &nbsp; fprintf(stderr, "Warning: %s (%s:%u, %s)\n", localMsg.constData(), context.file, context.line, context.function);&nbsp; &nbsp; &nbsp; &nbsp; break;&nbsp; &nbsp; case QtCriticalMsg:&nbsp; &nbsp; &nbsp; &nbsp; fprintf(stderr, "Critical: %s (%s:%u, %s)\n", localMsg.constData(), context.file, context.line, context.function);&nbsp; &nbsp; &nbsp; &nbsp; break;&nbsp; &nbsp; case QtFatalMsg:&nbsp; &nbsp; &nbsp; &nbsp; fprintf(stderr, "Fatal: %s (%s:%u, %s)\n", localMsg.constData(), context.file, context.line, context.function);&nbsp; &nbsp; &nbsp; &nbsp; abort();&nbsp; &nbsp; }}int main(int argc, char **argv){&nbsp; &nbsp; qInstallMessageHandler(myMessageOutput); // Install the handler&nbsp; &nbsp; QApplication app(argc, argv);&nbsp; &nbsp; ...&nbsp; &nbsp; return app.exec();}摘自qInstallMsgHandler（我仅添加了评论）的文档：QtMsgHandler qInstallMessageHandler（QtMsgHandler处理程序）在上面的示例中，该函数myMessageOutput使用stderr了您可能希望用其他文件流替换的函数，或者完全重写了该函数！一旦你写并安装此功能，您所有的qDebug（以及qWarning，qCritical等）消息将被重定向到你在处理程序写入文件。

Answer 2

从这里开始，所有的荣誉都归于精神。#include <QApplication>#include <QtDebug>#include <QFile>#include <QTextStream>void myMessageHandler(QtMsgType type, const QMessageLogContext &, const QString & msg){&nbsp; &nbsp; QString txt;&nbsp; &nbsp; switch (type) {&nbsp; &nbsp; case QtDebugMsg:&nbsp; &nbsp; &nbsp; &nbsp; txt = QString("Debug: %1").arg(msg);&nbsp; &nbsp; &nbsp; &nbsp; break;&nbsp; &nbsp; case QtWarningMsg:&nbsp; &nbsp; &nbsp; &nbsp; txt = QString("Warning: %1").arg(msg);&nbsp; &nbsp; break;&nbsp; &nbsp; case QtCriticalMsg:&nbsp; &nbsp; &nbsp; &nbsp; txt = QString("Critical: %1").arg(msg);&nbsp; &nbsp; break;&nbsp; &nbsp; case QtFatalMsg:&nbsp; &nbsp; &nbsp; &nbsp; txt = QString("Fatal: %1").arg(msg);&nbsp; &nbsp; break;&nbsp; &nbsp; }&nbsp; &nbsp; QFile outFile("log");&nbsp; &nbsp; outFile.open(QIODevice::WriteOnly | QIODevice::Append);&nbsp; &nbsp; QTextStream ts(&outFile);&nbsp; &nbsp; ts << txt << endl;}int main( int argc, char * argv[] ){&nbsp; &nbsp; QApplication app( argc, argv );&nbsp; &nbsp; qInstallMessageHandler(myMessageHandler);&nbsp; &nbsp;&nbsp; &nbsp; ...&nbsp; &nbsp; return app.exec();}

Answer 3

这是一个挂钩默认消息处理程序的工作示例。谢谢@Ross Rogers！// -- main.cpp// Get the default Qt message handler.static const QtMessageHandler QT_DEFAULT_MESSAGE_HANDLER = qInstallMessageHandler(0);void myCustomMessageHandler(QtMsgType type, const QMessageLogContext &context, const QString &msg){&nbsp; &nbsp; // Handle the messages!&nbsp; &nbsp; // Call the default handler.&nbsp; &nbsp; (*QT_DEFAULT_MESSAGE_HANDLER)(type, context, msg);}int main(int argc, char *argv[]){&nbsp; &nbsp; qInstallMessageHandler(myCustomMessageHandler);&nbsp; &nbsp; QApplication a(argc, argv);&nbsp; &nbsp; qDebug() << "Wello Horld!";&nbsp; &nbsp; return 0;}