title: Qtcreator can't find the class header file after promoting a widget to that class?
body: <p>I'm a newbie in Qt and not that much experienced in C++ either.</p>
  
  <p>I created simple Qt GUI app, but then I had to add the <code>mousepressevent</code> function on a <code>QLabel</code> type object, so I created the class which has the header file with following code:</p>
  
  <pre><code>#ifndef IMAGEACTION_H
  #define IMAGEACTION_H
  
  #include &lt;QLabel&gt;
  #include &lt;QMouseEvent&gt;
  #include &lt;QDebug&gt;
  #include &lt;QEvent&gt;
  
  class imageaction : public QLabel
  {
      Q_OBJECT
  public:
      explicit imageaction(QWidget *parent = 0);
      void mousePressEvent(QMouseEvent *ev);
  signals:
      void Mouse_Pressed();
  public slots:
  
  };
  
  #endif // IMAGEACTION_H
  </code></pre>
  
  <p>The <code>.cpp</code> file has the following code:</p>
  
  <pre><code>#include "imageaction.h"
  
  imageaction::imageaction(QWidget *parent) :
      QLabel(parent)
  {
  }
  
  void imageaction::mousePressEvent(QMouseEvent *ev)
  {
      emit Mouse_Pressed();
  }
  </code></pre>
  
  <p>In the <code>mainwindow.cpp</code> file added the line <code>#include "imageaction.h"</code> to include the header file and in the <code>.pro</code> file it's the following lines are also added:</p>
  
  <pre><code>SOURCES += main.cpp\
          mainwindow.cpp \
      imageaction.cpp
  
  
  HEADERS  += mainwindow.h \
      imageaction.h
  </code></pre>
  
  <p>But the program always gives the following error:</p>
  
  <p><code>C1083: Cannot open include file:'imageaction.h': No such file or directory</code>.</p>
  
  <p>Could you say where I'm making the mistake? To make this class I followed this <a href="https://www.youtube.com/watch?v=d0CDMtfefB4" rel="nofollow">video</a></p>