Implement QSortFilterProxyModel with own TreeModel?

Opa114

Hi there,

i have a own TreeModel whis is derived from QAbstractItemModel like in the QT Example (Editable TreeModel)

Now i want to make my TreeView sortable when i click on the table headers. I figured out that i can reimplement the sort()-function on my own inside my model or i can use QSortFilterProxyModel.

First what is the better or let's say mor practical way? i Think using QSortFilterProxyModel would be better, because i want to implement a filter function, too, which filtes the content of myTreeView. But i don't know how to integrate the QSortFilterProxyModel into my own Model. So i need there a little bit help from you. Would be great if someone could explain it in detail and maybe provide some small example code.

Thanks a lot!

Christian Ehrlicher

Go for the QSortFilterProxyModel. An example can be found here: http://doc.qt.io/qt-5/qtwidgets-itemviews-basicsortfiltermodel-example.html or http://doc.qt.io/qt-5/qtwidgets-itemviews-customsortfiltermodel-example.html

Opa114

Thanks for the information. I tried wo work on it a little bit.
I did a small example like this:

I implemented the EditableTreeModel form my first post) - the official qt example and then my small code looks like this inside the mainwidow.cpp

QStringList headers;
headers << tr("Title") << tr("Description");
model = new EditableTreeModel(headers, QString("Firtsname\tLastname\t"));


QSortFilterProxyModel *proxyModel = new QSortFilterProxyModel;
proxyModel->setSourceModel(model);
treeView->setModel(proxyModel);
treeView->setSortingEnabled(true);

So it works and sorting, too, if i add more data so that more rows where created but i have a problem, when i try to retrieve the data. I created a function which is called on double click inside a TreeView Item:

void MainWindow::on_treeView_doubleClicked(const QModelIndex &index)
{
qDebug() << "on_treeView_doubleClicked called";
qDebug() << model->data(index, Qt::DisplayRole);
}

Then i got the following output and error:

on_treeView_doubleClicked called

Trying to construct an instance of an invalid type, type id: 7890276

So it seems there is a problem with getting the data. So what i'm doing wrong? If i dont use the QSortFilterProxyModel the correct data retrieved.

mrjj

Hi
I think you need to use
http://doc.qt.io/qt-5/qsortfilterproxymodel.html#mapToSource
to look up data in the model.

Opa114

@mrjj

i think this was the problem:

qDebug() << model->data(index, Qt::DisplayRole);

i tried to get the datafrom the source model and not from the proxy model. After changing the line to getting data() from the proxy model it works and i get the right data. If i try to remove the selected row, the row (and data) will be removed from the underlying source model.

mrjj

@Opa114
Yes, that also works if you ask the proxy.
However, the model is unaware of the filtering so thats why
the given index didnt work with model.

Opa114

@mrjj
yes i understand what the problem is, but if it works directly with the proxy model it is better for me to work with that.

mrjj

@Opa114
Hi, nothing wrong working with the proxy :)

Opa114

@mrjj
Now i have another problem. I implemented a onDoubleClick Listener, which should return the data. My Treeview is set to expandAll(), because i have some TreeView entries which have children, like this structure:

- Root 1
    - Child 1
- Root 2
    - Child 2.1
    - Child 2.2
- Root 3

When i double click on one of the children my function return everytime the data from Root 1, so when i click on Child 2.2 i got the data from Root 1 and when i click on Child 1 i got the data from Root 1. I think something is worng with the indexes? But how can i solve this?

VRonin

@Opa114 said in Implement QSortFilterProxyModel with own TreeModel?:

I think something is worng with the indexes?

Good guess, can you show us your code?

Opa114

@VRonin said in Implement QSortFilterProxyModel with own TreeModel?:

Good guess, can you show us your code?

I solved it: I had to pass the parent index (tree structure), so the line should look like this:

QVariant data = m_proxy->data(m_proxy->index(index.row(), 4, index.parent()));