#include <QtGui/QApplication> 
#include <QtGui/QTreeView> 
#include <QtGui/QFileSystemModel> 

int main(int argc, char *argv[]) 
{ 
QApplication a(argc, argv); 

QFileSystemModel *model = new QFileSystemModel; 
model->setRootPath(""); 

QTreeView *tree = new QTreeView(); 
tree->setModel(model); 
tree->setRootIsDecorated(false); 
tree->setItemsExpandable(false); 
tree->show(); 

QObject::connect(tree, SIGNAL(doubleClicked(const QModelIndex&)), 
tree, SLOT(expand(const QModelIndex&))); 

return a.exec(); 
}