hi everybody

When I click on the "Click me" button , I get the message :

The program has unexpectedly finished.
Then program is closed !

TreeWidget.gif

why ?!

Qt Code: 
  1. #ifndef MAINWINDOW_H
  2. #define MAINWINDOW_H
  3. #include <QString>
  4. #include <QMainWindow>
  5. #include <QtCore>
  6. #include <QtGui>
  7. #include <QTreeWidget>
  8.  
  9. namespace Ui {
  10. class MainWindow;
  11. }
  12.  
  13. class MainWindow : public QMainWindow
  14. {
  15.     Q_OBJECT
  16.      void addRoot(QString name,QString dec);
  17.      void addChild(QTreeWidgetItem *parent,QString name,QString dec);
  18. public:
  19.     explicit MainWindow(QWidget *parent = 0);
  20.     ~MainWindow();
  21.  
  22.  
  23. private slots:
  24.      void on_pushButton_clicked();
  25.  
  26. private:
  27.     Ui::MainWindow *ui;
  28. };
  29.  
  30. #endif // MAINWINDOW_H
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Qt Code: 
  1. #include "mainwindow.h"
  2. #include "ui_mainwindow.h"
  3. #include <QTreeWidget>
  4. #include <QFont>
  5. MainWindow::MainWindow(QWidget *parent) :
  6.     QMainWindow(parent),
  7.     ui(new Ui::MainWindow)
  8. {
  9.     ui->setupUi(this);
  10.     ui->treeWidget->setColumnCount(2);
  11.     addRoot("Hello","World");
  12. }
  13.  
  14. MainWindow::~MainWindow()
  15. {
  16.     delete ui;
  17. }
  18.  
  19. void MainWindow::addRoot(QString name,QString dec)
  20. {
  21.     QTreeWidgetItem *ptr = new QTreeWidgetItem(ui->treeWidget) ;
  22.     ptr->setText(0,name);
  23.     ptr->setText(1,dec);
  24.     addChild(ptr,name,dec);
  25. }
  26. void MainWindow::addChild(QTreeWidgetItem *parent,QString name,QString dec)
  27. {
  29.     ptr1->setText(0,name);
  30.     ptr1->setText(1,dec);
  31.     parent->addChild(ptr1);
  32. }
  33.  
  34. void MainWindow::on_pushButton_clicked()
  35. {
  36.     QTreeWidgetItem *ptr = ui->treeWidget->currentItem();
  37.  
  38.     for(int i=0 ; i<100 ;i++)
  39.     {
  40.         ui->progressBar->setValue(i);
  41.         QThread::msleep(2);
  42.     }
  43.     if(ptr->isSelected())
  44.     {
  45.     ptr->setBackgroundColor(0,Qt::red);
  46.     ptr->setBackgroundColor(1,Qt::red);
  47.     }
  48. }
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