QTreeView appears un-ordered and without a scrollbar on startup

[karabaja4]

Hello,

I have a problem making QTreeView work as expected.

I'm trying to make a simple filesystem tree using QFileSystemModel. I made this to work, but when I start my application, in the first 0.5 - 1 seconds of running the program the tree appears un-ordered (beginning with the home folder) and without a scrollbar. Example pictures are as follows:

This is as it appears on the cold startup for the first 0.5 - 1 seconds:



This is as it appears after the previous image, that is, after 0.5 - 1 seconds:



My code is as follows:

mainwindow.cpp

#include <QtGui>
 
#include "mainwindow.h"
 
MainWindow::MainWindow() {
 
    QString startPath = QDir::currentPath();
 
    // create system models ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
    treeModel  = new QFileSystemModel(this);
    treeModel->setFilter(QDir::NoDotAndDotDot | QDir::AllDirs);
    treeModel->setRootPath("/");
 
    // tree ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
    treeDock = new QDockWidget("Tree view", this);
    treeView = new QTreeView(treeDock);
 
    QWidget* dummyWidget = new QWidget(); //remove dock titlebar
    treeDock->setTitleBarWidget(dummyWidget);
 
    treeView->setModel(treeModel);
    treeView->setHeaderHidden(true); //no headers
    treeView->setUniformRowHeights(false); //better performance
    treeView->hideColumn(1);
    treeView->hideColumn(2);
    treeView->hideColumn(3);
    treeView->hideColumn(4);
 
    treeView->setRootIndex(treeModel->index("/"));
    treeView->setCurrentIndex(treeModel->index(startPath));
    treeView->scrollTo(treeModel->index(startPath));
 
    treeDock->setWidget(treeView); //add tree to dock
    this->addDockWidget(Qt::LeftDockWidgetArea, treeDock);
 
    // statusbar ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    status = statusBar();
 
}

#include <QtGui>

#include "mainwindow.h"

MainWindow::MainWindow() {

    QString startPath = QDir::currentPath();

    // create system models ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    treeModel  = new QFileSystemModel(this);
    treeModel->setFilter(QDir::NoDotAndDotDot | QDir::AllDirs);
    treeModel->setRootPath("/");

    // tree ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    treeDock = new QDockWidget("Tree view", this);
    treeView = new QTreeView(treeDock);

    QWidget* dummyWidget = new QWidget(); //remove dock titlebar
    treeDock->setTitleBarWidget(dummyWidget);

    treeView->setModel(treeModel);
    treeView->setHeaderHidden(true); //no headers
    treeView->setUniformRowHeights(false); //better performance
    treeView->hideColumn(1);
    treeView->hideColumn(2);
    treeView->hideColumn(3);
    treeView->hideColumn(4);

    treeView->setRootIndex(treeModel->index("/"));
    treeView->setCurrentIndex(treeModel->index(startPath));
    treeView->scrollTo(treeModel->index(startPath));

    treeDock->setWidget(treeView); //add tree to dock
    this->addDockWidget(Qt::LeftDockWidgetArea, treeDock);

    // statusbar ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    status = statusBar();

}

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(I do need the dock)

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
 
#include <QMainWindow>
#include <QtCore>
#include <QtGui>
 
class MainWindow : public QMainWindow
{
    Q_OBJECT
 
public:
    MainWindow();
 
private:
    QFileSystemModel *treeModel;
    QTreeView *treeView;
    QDockWidget *treeDock;
    QStatusBar *status;
    QMenuBar *menuBar;
 
};
 
#endif // MAINWINDOW_H

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QtCore>
#include <QtGui>

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow();

private:
    QFileSystemModel *treeModel;
    QTreeView *treeView;
    QDockWidget *treeDock;
    QStatusBar *status;
    QMenuBar *menuBar;

};

#endif // MAINWINDOW_H

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main.cpp

#include <QtGui/QApplication>
#include "mainwindow.h"
 
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
 
    return a.exec();
}

#include <QtGui/QApplication>
#include "mainwindow.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    return a.exec();
}

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=> My QTCreator project file: download here

*

=> I forgot to mention the problem (maybe I wasn't clear), I'm trying to eliminate that interval when the tree is un-ordered and without a scrollbar. I want it to appear like in the second picture from the start.

I was going nuts trying to solve this but no luck...
Any help would be greatly appreciated!

[wysota]

QFileSystemModel fills itself on demand using a worker thread. Thanks to that it doesn't block the application while directories are being scanned. If you want to eliminate this behaviour then either use QDirModel instead of QFileSystemModel or wait until the model is populated before showing it in the tree.

[karabaja4]

QFileSystemModel fills itself on demand using a worker thread. Thanks to that it doesn't block the application while directories are being scanned. If you want to eliminate this behaviour then either use QDirModel instead of QFileSystemModel or wait until the model is populated before showing it in the tree.

This (the bolded part) is what I want to do, but I have no idea what code to use.

[wysota]

Don't set the model on the tree until it finishes populating.

[Santosh Reddy]

Qt Documentation says QDirModel is obsolete.

Don't set the model on the tree until it finishes populating.

directoryLoaded() signal can be used, set the view model in the slot connected to this signal

[wschenke]

I use a work-around for the described (a little ugly) behaviour.
Derive a class MyTreeView from QTreeView and add the following:

mytreeview.h:

Q_SLOT
void onDirectoryLoaded(const QString&);

Q_SLOT
void onDirectoryLoaded(const QString&);

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mytreeview.cpp:

void YFileTree::onDirectoryLoaded(const QString&)
{
Model->sort(0); // the column for sorting
}
 
MyTreeView::MyTreeView()
{
// ...
connect(Model,SIGNAL(directoryLoaded(const QString&)),
        this,SLOT(onDirectoryLoaded(const QString&)));
// ...
}

void YFileTree::onDirectoryLoaded(const QString&)
{
Model->sort(0); // the column for sorting
}

MyTreeView::MyTreeView()
{
// ...
connect(Model,SIGNAL(directoryLoaded(const QString&)),
        this,SLOT(onDirectoryLoaded(const QString&)));
// ...
}

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