Queston is specific: How to change icon after QFileSystemModel bind to system directory. To realize image preview.

Next time please describe more details in your post, we do not have supernatual power, it is hard to guess what do you want to do. Your problem may seem obvious to yourself, but usually this is not true for other, that is why we need to give more information when asking questions.

If you want to post your codes and expect us to read it, please make a minimal one, make your classes, functions as short as possible(I believe most of us think small classes and functions easier to read than large one), do not put all of the codes at once. Your long classes and functions may seem clear for you within 3 months, but not for other.

void QFileSystemModel::setIconProvider(QFileIconProvider *provider)
Sets the provider of file icons for the directory model.

Try it again.

QIcon QFileSystemModel::fileIcon(const QModelIndex &index) const
Returns the icon for the item stored in the model under the given index.

we can get the QIcon from the QFileSystemModel from QModelIndex. How to set the QIcon ?

would you try setdata use the QFileSystemModel::FileIconRole ?