How to wait for QFileSystemModel so that rowCount() != 0

  • Hi,

    From the Documentation:
    Unlike QDirModel, QFileSystemModel uses a separate thread to populate itself so it will not cause the main thread to hang as the file system is being queried. Calls to rowCount() will return 0 until the model populates a directory.

    What is the right way to wait for QFileSystemModel to finish it's procedure?

    @ QFileSystemModel *fileModel;
    QModelIndex parentIndex = fileModel->index(path);
    int numRows = fileModel->rowCount(parentIndex);@

  • Lifetime Qt Champion


    The "directoryLoaded": signal might be a good starting point

    Hope it helps

  • Hi SGaist,

    i think i am accessing the signal in a wrong way,

    In Widget.cpp:

    dirModel = new MyQFileSystemModel;
    connect(dirModel, SIGNAL(​directoryLoaded(const QString &)), this, SLOT(toggled(const QString&)));@

    in Widget.h:
    void directoryLoaded(const QString &path);

    public slots:
    void toggled(const QString &path);@

    Am i doing something wrong?
    Error: No such signal QFileSystemModel::?directoryLoaded(const QString &)

  • Lifetime Qt Champion

    Yes you do, your SIGNAL and SLOT statements are wrong.

    connect(dirModel, SIGNAL(​directoryLoaded(QString)), this, SLOT(toggled(QString)));

    Out of curiosity, why the directoryLoaded in Widget.h ?

  • Hi SGaist, still does not work
    QObject::connect: No such signal QFileSystemModel::?directoryLoaded(QString) in ..\AssetBrowser_02\widget.cpp:126

    Out of curiosity, why the directoryLoaded in Widget.h ?

    Do you mean in terms of Programm-Design? I am prototyping in widget.cpp and encapsulating it later in the appropriate classes.

  • Lifetime Qt Champion

    Looks like you implement a custom MyQFileSystemModel, how does it look like ?

    Can you show again your connect statement ?

  • SGaist,

    i just have overwritten the data in my custom MyQFileSystemModel:
    @class MyQFileSystemModel : public QFileSystemModel {
    QVariant data( const QModelIndex& index, int role ) const {

        if( role == Qt::DecorationRole ) {
            return QVariant(QIcon(QPixmap(":/myresources/images/folder-icon.png")));
        return QFileSystemModel::data(index, role);


    My Connect Statement:
    @connect(dirModel, SIGNAL(​directoryLoaded(QString)), this, SLOT(toggled(QString)));@

  • Lifetime Qt Champion

    You can also use a QIdentityProxyModel for such customization. That allows to reuse the same QFileSystemModel with several views (if you need such a thing)

    What version of Qt are you using ?

  • I think SGaist's solution is the better one. Furtheremore, your subclass is not complete: no Q_OBJECT macro, no constructor, etc.

  • I am using version 5.4. The constructor should be derived from the base-class. Can the macro be derived as well? I don't know whats happening deep inside QT.

    Ok now with the proxy model i get a runtime debug message:
    QAbstractItemView::setRootIndex failed : index must be from the currently set model

    I was setting the root Index like this:

    I don't know if the error is coming from this part of the code, but seems to be, as i am only setting the root Index here. So how can i set now the index? The Proxy Model has no methods for that.

    Thanks in advance

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