QT MVC 模式不更新视图 - 特定的 SimpleTreeModel 示例

Question

I have had problems in my own code to get the views to update after model data is updated.

I then took the SimpleTree example from QT and added a timer in TreeModel to change the data after 10s and then invoke the same set data function used in the constructor to update the model. The code is below for the slot that executes on the timer timeout. No matter what I try, the view does not update. The setDate and emit dataChanged were some attempts.

In my own code, I have a XML-RPC call updating the data, but considering I dont even get the simpleTreeModel to work, I suppose that would be a long shot.

Is there something fundamental that I am missing here?

void TreeModel::slotTimeout(void)
{
   QStringList tmp;
   tmp << "qaz";
   tmp << "wsx";
   tmp << "edc";
   setupModelData(tmp,rootItem);
   setData(QModelIndex(),QModelIndex());
   emit dataChanged(QModelIndex(), QModelIndex());
   qDebug() << "Timer update";
}

Answer 1

The SimpleTreeModel example is for static models only. It lacks the implementation of the required QAbstractItemModel functions to update the model.

Have a look on the detailed description of the models documentation in order to see what should be implemented.

The problem is, that the required methods are implemented as empty methods by default so you will not get any error messages if something is missing. It will just not work.

In addition it'sa bit tricky to do the necessary data changed emits.

Within the setData method you have to emit dataChanged() .

Within the also necessary insertRows you have to call the methods beginInsertRows(...) and endInsertRows() in order to get the required signals emitted.

A first approach toward the MV paradigma is to use the QStandardItemModel . It provides all the necessary implementation if a QStandardItem is sufficient what it usually will be.