use QFileSystemModel

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QtGui>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    auto model = new QFileSystemModel;
    auto index = model->setRootPath("C:/Users/Atsushi4/workspace");
    ui->treeView->setModel(model);
    ui->treeView->setRootIndex(index);
    ui->treeView->setCurrentIndex(index.child(0,0));

    ui->treeView->setSortingEnabled(true);
}

MainWindow::~MainWindow()
{
    delete ui;
}