QFileSystemModel and QSortFilterProxyModel don't work well together?

[solotim]

Hi, I found that QSortFilterProxyModel can't filter properly when it works with QFileSystemModel. Sometimes it left NOTHING in the view. Can anyone point out where I'm wrong?

Just create a simple GUI example:

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    QFileSystemModel *fsm = new QFileSystemModel(this);
    fsm->setRootPath(".");
 
    QSortFilterProxyModel *sfpm = new QSortFilterProxyModel();
    sfpm->setDynamicSortFilter(true);
    sfpm->setSourceModel(fsm);
    sfpm->setFilterRegExp(QRegExp(".cpp", Qt::CaseInsensitive,
                                  QRegExp::FixedString));
    sfpm->setFilterKeyColumn(0);
 
    ui->tableView->setModel(sfpm);
 
    ui->tableView->setRootIndex(sfpm->mapFromSource(fsm->index(".")));
 
 
}

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    QFileSystemModel *fsm = new QFileSystemModel(this);
    fsm->setRootPath(".");

    QSortFilterProxyModel *sfpm = new QSortFilterProxyModel();
    sfpm->setDynamicSortFilter(true);
    sfpm->setSourceModel(fsm);
    sfpm->setFilterRegExp(QRegExp(".cpp", Qt::CaseInsensitive,
                                  QRegExp::FixedString));
    sfpm->setFilterKeyColumn(0);

    ui->tableView->setModel(sfpm);

    ui->tableView->setRootIndex(sfpm->mapFromSource(fsm->index(".")));


}

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if you comment out the setFilterRegExp statement, sure the files in current path are shown in the view. I've also tried setFilterWildcard and other RegExp, nothing works. Very frustrating.