Dear All

I have problem about my application which is Qt 4.8.1 when using QFuture and QtConcurrent i get error code

QObject::setParent: Cannot set parent, new parent is in a different thread
QPixmap: It is not safe to use pixmaps outside the GUI thread
QObject::startTimer: timers cannot be started from another thread
QObject::setParent: Cannot set parent, new parent is in a different thread

And also my application keep crushing unexpectedly. I never know when it going to crush.

I would be so happy is someone can help me.

Here is my code
tryfuture.h
Qt Code: 
  1. #ifndef TRYFUTURE_H
  2. #define TRYFUTURE_H
  3.  
  4. #include <QtGui>
  5. #include <QDialog>
  6. #include <QMessageBox>
  7. #include <QTime>
  8. #include <qtconcurrentrun.h>
  9. #include <QThread>
  10.  
  11. namespace Ui {
  12. class tryfuture;
  13. }
  14.  
  15. class tryfuture: public QWidget
  16. {
  17.     Q_OBJECT
  18.     int pagenumber;
  19. public:
  20.     explicit tryfuture(QWidget *parent = 0);
  21.     ~tryfuture();
  22. public slots:
  23.     void test1();
  24.     void test2();
  25.     void test3();
  26. private:
  27.     Ui::tryfuture*ui;
  28. };
  29. #endif //
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tryfuture.cpp
Qt Code: 
  1. tryfuture::tryfuture(QWidget *parent) :
  2.     QWidget(parent),
  3.     ui(new Ui::tryfuture)
  4. {
  5.  
  6.     QTimer *changetimer= new QTimer(this);
  7.     connect(changetimer, SIGNAL(timeout()), this, SLOT(changepage()));
  8.     changetimer->start(10000);
  9.  
  10. }
  11.  
  12. void tryfuture::changepage(){
  13.  
  14.     QFuture<void> future;
  15.  
  16.     switch(pagenumber%3)
  17.     {
  18.     case 0:
  19.         future = QtConcurrent::run(this, &tryfuture::test1);
  20.         break;
  21.     case 1:
  22.         future = QtConcurrent::run(this, &tryfuture::test2);
  23.         break;
  24.     case 2:
  25.         future = QtConcurrent::run(this, &tryfuture::test3);
  26.         break;
  27.     }
  28.  
  29.     pagenumber++;
  30. }
  31. void tryfuture::test1(){
  32.     QMessageBox::information(this, tr("Qt Example 1"),
  33.                              tr("The function my_func has finished."));
  34. }
  35.  
  36. void tryfuture::test2(){
  37.     QMessageBox::information(this, tr("Qt Example 2"),
  38.                              tr("The function my_func has finished."));
  39. }
  40. void formUretimBilgiEkrani::test3(){
  41.     QMessageBox::information(this, tr("Qt Example 3"),
  42.                              tr("The function my_func has finished."));
  43. }
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