I'm building a timer with an interval that can adjusted by a slider. Here's a shot of my ui:

yooeye.jpg

The upper lcdNumber counts up by one every second. I want to use the slider to speed it up and slow it down. Here is my header file

Qt Code: 
  1. #ifndef MAINWINDOW_H
  2. #define MAINWINDOW_H
  3.  
  4. #include <QMainWindow>
  5.  
  6. namespace Ui {
  7. class MainWindow;
  8. }
  9.  
  10. class MainWindow : public QMainWindow
  11. {
  12.     Q_OBJECT
  13.  
  14. public:
  15.     explicit MainWindow(QWidget *parent = 0);
  16.     ~MainWindow();
  17.     QTimer *timer;  // here the timer is made public
  18.  
  19. private:
  20.     Ui::MainWindow *ui;
  21.  
  22. private slots:
  23.     void inkup();
  24.     void on_horizontalSlider_valueChanged(int value);
  25. };
  26.  
  27. #endif // MAINWINDOW_H
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And here is my application

Qt Code: 
  1. #include "mainwindow.h"
  2. #include "ui_mainwindow.h"
  3. #include "qapplication.h"
  4. #include <QtWidgets>
  5.  
  6. MainWindow::MainWindow(QWidget *parent) :
  7.     QMainWindow(parent),
  8.     ui(new Ui::MainWindow)
  9. {
  10.     ui->setupUi(this);
  11.  
  12.     QTimer *timer = new QTimer(this);
  13.     connect(timer, SIGNAL(timeout()), this, SLOT(inkup()));
  14.     timer->start(1000);
  15. }
  16.  
  17. void MainWindow::inkup() {
  18. int eks = ui->lcdNumber->value();
  19.     eks += 1;
  20.     ui->lcdNumber->display(eks);
  21. }
  22.  
  23. MainWindow::~MainWindow()
  24. {
  25.     delete ui;
  26. }
  27.  
  28. void MainWindow::on_horizontalSlider_valueChanged(int speed)
  29. {
  30.     ui->lcdNumber_2->display(timer->remainingTime());
  31.  
  32.     ui->lcdNumber_2->display(speed);
  33.  
  34.     timer->setInterval(speed);  // this causes a crash at run time
  35. }
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In the horizontal slider event handler, I can display in the second lcdNumber the timer property remainingTime(). No problem. I can display the changed slider value so I know it's okay. But when I try and set the timer interval I get a run time crash. In fact most of the properties that pop up for the timer when I type timer-> also cause a crash. What am I doing wrong?