[Qt-interest] QTreeView, QFileSystemModel, setRootPath and QSortFilterProxyModel with RegExp for filtering

[Andre Somers]

On 9-7-2010 14:14, Sven Grunewaldt wrote:
> I need to show a QTreeView of a specific directory and I want to give
> the user the possibility to filter the files with a RegExp.
>
> As I understand the Qt Documentation I can achieve this with the classes
> mentioned in the subject like this:
>
>      // Create the Models
>      QFileSystemModel *fileSystemModel = new QFileSystemModel(this);
>      QSortFilterProxyModel *proxyModel = new QSortFilterProxyModel(this);
>
>      // Set the Root Path
>      QModelIndex rootModelIndex =
>          fileSystemModel->setRootPath("E:\\example");
>
>      // Assign the Model to the Proxy and the Proxy to the View
>      proxyModel->setSourceModel(fileSystemModel);
>      ui->fileSystemView->setModel(proxyModel);
>
>      // Fix the TreeView on the Root Path of the Model
>      ui->fileSystemView->setRootIndex(
>          proxyModel->mapFromSource(rootModelIndex));
>
>      // Set the RegExp when the user enters it
>      connect(ui->nameFilterLineEdit, SIGNAL(textChanged(QString)),
>              proxyModel, SLOT(setFilterRegExp(QString)));
>
> When starting the program the TreeView is correctly fixed to the
> specified directory. But as soon as the user changes the RegExp it seems
> like the TreeView forgets its RootIndex. After removing all text in the
> RegExp LineEdit (or entering a RegExp like ".") it shows all directories
> again (on Windows this means all drives and so on)
>
> What am I doing wrong? :/
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>
>    
What I think is happening, is that as soon as you start filtering, the 
index you use as your root does no longer exist. The view then resets to 
an invalid index as the root index. The filtering works on the whole 
model tree, not just on the part you see if you start to enter your filter!

I think you are going to need a modified proxy model to do what you 
want. It should only apply the filtering on items under your root path, 
but let the root path itself (and everything else) alone.

André

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