Associate data with child items in listView

[moiit]

Hello folks,
I have spent hours of time on how to assign data to a child item in a listView.
What's wrong? Please help!

#include <QApplication>
#include <QtDebug>
#include <QtCore>
#include <QtGui>
 
int main(int argc, char** argv)
{
  QApplication app(argc, argv);
  QMainWindow window;
 
  QSplitter *sp=new QSplitter;
    QListView *listView1=new QListView;
    QListView *listView2=new QListView;
    sp->addWidget(listView1);
    sp->addWidget(listView2);
 
    QStandardItemModel model;
 
    QStandardItem *group1 = new QStandardItem("Music Group 1");
 
    QStandardItem *music1=new QStandardItem("Music 1");
    music1->setData("Some datails", Qt::UserRole);
    qDebug()<<model.data(model.index(0,0).child(0,0), Qt::UserRole);
 
    group1->appendRow(music1);
 
    model.appendRow(group1);
 
    QStandardItem *group2 = new QStandardItem("Music Group 2");
 
    QStandardItem *music2=new QStandardItem("Music 2");
    qDebug()<<model.data(model.index(1,0).child(0,0), Qt::UserRole);
 
    group2->appendRow(music2);
 
    model.appendRow(group2);
 
    listView1->setModel(&model);
    listView1->setRootIndex(QModelIndex());
    listView2->setModel(&model);
 
    QObject::connect(listView1, SIGNAL(clicked(const QModelIndex&)),
                     listView2, SLOT(setRootIndex(const QModelIndex&)));
 
  window.setCentralWidget(sp);
  window.show();
 
  return app.exec();
}

#include <QApplication>
#include <QtDebug>
#include <QtCore>
#include <QtGui>

int main(int argc, char** argv)
{
  QApplication app(argc, argv);
  QMainWindow window;

  QSplitter *sp=new QSplitter;
    QListView *listView1=new QListView;
    QListView *listView2=new QListView;
    sp->addWidget(listView1);
    sp->addWidget(listView2);

    QStandardItemModel model;

    QStandardItem *group1 = new QStandardItem("Music Group 1");

    QStandardItem *music1=new QStandardItem("Music 1");
    music1->setData("Some datails", Qt::UserRole);
    qDebug()<<model.data(model.index(0,0).child(0,0), Qt::UserRole);

    group1->appendRow(music1);

    model.appendRow(group1);

    QStandardItem *group2 = new QStandardItem("Music Group 2");

    QStandardItem *music2=new QStandardItem("Music 2");
    qDebug()<<model.data(model.index(1,0).child(0,0), Qt::UserRole);

    group2->appendRow(music2);

    model.appendRow(group2);

    listView1->setModel(&model);
    listView1->setRootIndex(QModelIndex());
    listView2->setModel(&model);

    QObject::connect(listView1, SIGNAL(clicked(const QModelIndex&)),
                     listView2, SLOT(setRootIndex(const QModelIndex&)));
  
  window.setCentralWidget(sp);
  window.show();

  return app.exec();
}

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Result:

QVariant(, )
QVariant(, )

QVariant(, )
QVariant(, )

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It seems that the parent items are showed fine, and the corresponding data are retrieved. But the child item & its data are invalid.

Any advice is grateful!