qt xml

#include "mainwidget.h"
#include "ui_mainwidget.h"

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

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

void MainWidget::on_pushButton_clicked()
{
    QXmlStreamReader xmlReader;
    xmlReader.addData(ui->textBrowser->toPlainText());

    ui->treeWidget->clear();
    QStack<QTreeWidgetItem*> widgetStack;

    while (!xmlReader.atEnd()){
        if (xmlReader.isStartElement()){
            QStringList sl;
            sl << xmlReader.name().toString();
            QTreeWidgetItem* item = new QTreeWidgetItem(sl);
                if (widgetStack.count()==0){
                    ui->treeWidget->addTopLevelItem(item);
        }
                else {
                    widgetStack.top()->addChild(item);
                }
                widgetStack.push(item);
        }
        if (xmlReader.isEndElement()){
            widgetStack.pop();

        }

        xmlReader.readNext();
    }
}

void MainWidget::on_pushButton_2_clicked()
{
    QString filename=QFileDialog::getOpenFileName(
                this,
                tr("Otwórz plik"),
                "C:\\",
                "Pliki XML (*.xml)"
                );

    QFile file(filename);

    if(!file.open(QIODevice::ReadOnly))

        {
        QMessageBox::information(0,"Błąd",file.errorString());
        }

    QTextStream input(&file);

    ui->textBrowser->setText(input.readAll());

}