Hi there. I have a problem I would like you to help me with. Here is my code.

Qt Code: 
  1. #include "qplotter.h"
  2.  
  3. QPlotter::QPlotter(QMainWindow *parent) :
  4.     QMainWindow(parent)
  5. {
  6.     create_actions();
  7.     create_file_test("d:\\my_projects\\1.txt");
  8.     read_file("d:\\my_projects\\1.txt");
  9.     create_menus();
  10.     plot_item();
  11.  
  12.     //connect(loadFileAction, SIGNAL(triggered()), this, SLOT(repaint()));
  13. }
  14.  
  15. void QPlotter::repaint()
  16. {
  17.     funPlot->resize(this->size());
  18. }
  19.  
  20. void QPlotter::plot_item()
  21. {
  22.      QwtPlotCurve* temp_curve = new QwtPlotCurve();
  23.      QPen pen = QPen(Qt::blue);
  24.      temp_curve->setRenderHint(QwtPlotItem::RenderAntialiased);
  25.      temp_curve->setPen(pen);
  26.      temp_curve->setData(y_points, x_points);
  27.      temp_curve->setVisible(true);
  28.      temp_curve->setTitle("Channel 1, blue");
  29.  
  30.      funPlot = new QwtPlot(this);
  31.      funPlot->setTitle("Channel 1");
  32.      temp_curve->attach(funPlot);
  33.  
  34.      funPlot->resize(800, 600);
  35.  
  36.      QwtLegend* legend = new QwtLegend(this);
  37.      funPlot->insertLegend(legend, QwtPlot::RightLegend, -1.0);
  38.  
  39.      this->resize(funPlot->size());
  40.  
  41.      this->repaint();
  42. }
  43.  
  44. void QPlotter::create_actions()
  45. {
  46.     loadFileAction = new QAction(tr("Load file..."),this);
  47.     saveCurveAsImageAction = new QAction(tr("Save as image..."), this);
  48. }
  49.  
  50. void QPlotter::create_menus()
  51. {
  52.     fileMenu = new QMenu();
  53.     this->menuBar()->addMenu(fileMenu);
  54.  
  55.     fileMenu->setTitle("File");
  56.     fileMenu->addAction(loadFileAction);
  57.     fileMenu->addAction(saveCurveAsImageAction);
  58. }
  59.  
  60. void QPlotter::create_file_test(char* name)
  61. {
  62.     FILE* in_file;
  63.     in_file = fopen(name, "w");
  64.  
  65.     //create and fill vectors with test values
  66.     std::vector<float> a, b;
  67.  
  68.     for (int i = 0; i < 10000; i+=50) a.push_back(i);
  69.     for (int i = 0; i < 200; i++) b.push_back(i);
  70.  
  71.     for (int i = 0; i < 200; i++) fprintf(in_file, "%f %f\n", b[i], a[i]);
  72.     fclose(in_file);
  73. }
  74.  
  75. void QPlotter::read_file(char* name)
  76. {
  77.     FILE* in_file;
  78.     in_file = fopen(name, "r");
  79.  
  80.     rewind(in_file);
  81.  
  82.     float* temp1 = (float*)calloc(1, sizeof(float));
  83.     float* temp2 = (float*)calloc(1, sizeof(float));
  84.     while (!feof(in_file))
  85.     {
  86.             fscanf(in_file, "%f %f", temp1, temp2);
  87.             x_points.push_back(*temp1);
  88.             y_points.push_back(*temp2);
  89.     }
  90.  
  91.     int k = 0;
  92.  
  93.     free(temp1);//free allocated memory
  94.     free(temp2);//free allocated memory
  95. }
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But after executing plot_item(), the menu is no longer clickable. If create_menus() is placed after plot_item(), everything works. What am I doing wrong? Thank you in advance.