如何使用Qt打印到控制台 [英] How to print to console when using Qt

问题描述

我使用Qt4和C ++在计算机图形学中制作一些程序。我需要能够在运行时打印一些变量，而不是调试，但 cout 似乎不工作，即使我添加库。

解决方案

如果它足够打印到 stderr ，您可以使用以下最初用于调试的流：

  // qInfo是qt5.5 + 。 
 qInfo（）<< C ++ Style Info Message; 
 qInfo（C Style Info Message）; 
 
 qDebug（）<< C ++ Style Debug Message; 
 qDebug（C Style Debug Message）; 
 
 qWarning（）<< C ++ Style Warning Message; 
 qWarning（C Style Warning Message）; 
 
 qCritical（）<< C ++ Style Critical Error Message; 
 qCritical（C风格严重错误消息）; 
 
 // qFatal没有C ++样式方法。 
 qFatal（C Style Fatal Error Message）; 
  

虽然在评论中指出，记住qDebug消息如果 QT_NO_DEBUG_OUTPUT

如果你需要stdout，你可以尝试这样（像Kyle Strand指出的那样）：

  QTextStream& qStdOut（）
 {
 static QTextStream ts（stdout）; 
 return ts; 
} 
  

然后您可以按如下方式调用：

  qStdOut（）< std out！; 
  

I'm using Qt4 and C++ for making some programs in computer graphics. I need to be able to print some variables in my console at run-time, not debugging, but cout doesn't seem to work even if I add the libraries. Is there a way to do this?

解决方案

If it is good enough to print to stderr, you can use the following streams originally intended for debugging:

//qInfo is qt5.5+ only.
qInfo() << "C++ Style Info Message";
qInfo( "C Style Info Message" );

qDebug() << "C++ Style Debug Message";
qDebug( "C Style Debug Message" );

qWarning() << "C++ Style Warning Message";
qWarning( "C Style Warning Message" );

qCritical() << "C++ Style Critical Error Message";
qCritical( "C Style Critical Error Message" );

// qFatal does not have a C++ style method.
qFatal( "C Style Fatal Error Message" );

Though as pointed out in the comments, bear in mind qDebug messages are removed if QT_NO_DEBUG_OUTPUT is defined

If you need stdout you could try something like this (as Kyle Strand has pointed out):

QTextStream& qStdOut()
{
    static QTextStream ts( stdout );
    return ts;
}

You could then call as follows:

qStdOut() << "std out!";

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