QTableView Not Updating After Adding a New Row

Satish Joshi

Hey Folks

Hope you all are doing Well.

I have through a lot of similar links regarding the issue which I am getting on the Table view. Here's the code with its explanation :

// Declared on the header file
QStandardItemModel* model;

// Intialization on Constructor
    model = new QStandardItemModel(0,0,this);

// Here's the logic behind the view which I am showing on QsubWindow
tableView = new QTableView(this);
    tableView->setModel(model);
    tableView->verticalHeader()->setVisible(false);
    tableView->verticalHeader()->setDefaultSectionSize(10);

    for(int i = 0; i < clusterNames.length(); i++) {
        QStandardItem *clusterName_i = new QStandardItem(clusterNames[i]);
        QStandardItem *clusterIP_i = new QStandardItem(clusterIPs[i]);

        model->setItem(i, 0, clusterName_i);
        model->setItem(i, 1, clusterIP_i);
    }

    tableView->viewport()->update();

    splitter = new QSplitter(this);
    splitter->setOrientation(Qt::Horizontal);
    splitter->addWidget(hwTreeContainer);
    splitter->addWidget(tableView);

// Then I used to display it on the window which is basically a QsubWindow.

Explanation: The Logic behind this is I am populating a dialog on the window and adding the details which are used to show on the table view. After closing that particular Qdialog I noticed that the new row has not been added to the Table View but if I reopen the window I see the updated view with updated rows on the table view.

The issue I am getting is that my Table View isn't updating automatically after adding or inserting the new data. But if I reopen the same window then I see the updated things.

If anyone could help me regarding this would be a great help.

Thanks in Advance

raven-worx

@Satish-Joshi
you initialize your model with no rows and no columns. Then you set the model to your view.
The model never notifies the the view about a new row.

so either you

initialize your model with the correct row & column count, or
call QStandardItemModel::insertRow() before your setItem() calls

MasterBLB

void QStandardItemModel::appendRow(const QList<QStandardItem *> &items) is your friend Brother:

for (int i = 0; i < clusterNames.length(); i++)
{
    model->appendRow( { new QStandardItem(clusterNames[i]), new QStandardItem(clusterIPs[i]) } );
}

Satish Joshi

@raven-worx

First of all, Thank you so much for your time.

As you mentioned that I am initializing the model with no rows and no columns. The reason behind it as I checked my model has updated data by debugging it but somehow it couldn't be able to show on the view.

I also used QStandardItemModel::insertRow() in my code like this :

model->insertRow(model->rowCount());

  for(int i = 0; i < clusterNames.length(); i++) {
      QStandardItem *clusterName_i = new QStandardItem(clusterNames[i]);
      QStandardItem *clusterIP_i = new QStandardItem(clusterIPs[i]);

      model->setItem(i, 0, clusterName_i);
      model->setItem(i, 1, clusterIP_i);
  }

But sadly it didn't work or I am missing something. As I am calling the constructor of the current class (Where my logic has been there) after adding the new data which is in a different class of QDialog type. As I will share the glimpse of my QSubWindow type class constructor :

HardwareDlg::HardwareDlg(QWidget *parent) :
    QMdiSubWindow(parent),
    ui(new Ui::HardwareDlg)
{        
    this->setWindowTitle(HWWINDOW_NAME);
    this->resize(1200, 550);

    model = new QStandardItemModel(this);

    createActions();
    createMenus();
    newDeviceAct->setVisible(false);
    newDatagroupAct->setVisible(false);
    if (newMenu) {
        newMenu->setTitle("");
    }

    getClusterList();
    createStatusLabel();
    createMainView();  // This is the function which shows the data on table view and the main logic is written here
    createTreeView();
}

Also, I am attaching a screenshot so that it will briefer you :

Please help me regarding this as I am stuck in this issue for like more than 2 days

Satish Joshi

@MasterBLB

Thank You so much for your time brother.

But sadly it didn't work. Actually, I want the view to update automatically after adding the new row through a dialog box. As I can see the changes if I reopen the particular window again.

Also, my model has the updated data but somehow I don't know why table view is not updating.

Thanks

MasterBLB

Hmmm...try emit dataChanged(model->index(i, 0), model->index(i, 1), <maybe you'll have to pass 3rd parameter as well>) just after the line which adds new row.
If that won't help then there are last resort methods - beginResetModel() before adding rows, and after completing add row operation endResetModel()
Soo, merging my answers so far the output code would be:

for (int i = 0; i < clusterNames.length(); i++)
{
    model->appendRow( { new QStandardItem(clusterNames[i]), new QStandardItem(clusterIPs[i]) } );
    emit dataChanged(model->index(i, 0), model->index(i, 1));//maybe you'll have to pass 3rd parameter as well
}

raven-worx

@Satish-Joshi said in QTableView Not Updating After Adding a New Row:

Actually, I want the view to update automatically after adding the new row through a dialog box.

i explained why it doesnt update.
What exactly have you tried?!

Satish Joshi

@raven-worx

Yes I understand what you trying to explain and have used your suggested approach and
I have used QStandardItemModel::insertRow(). But it didn't work.

Thanks

Satish Joshi

@MasterBLB

you mean to say QAbstractItemModel::dataChanged(.....) right?

I did it like this way :

// In header File
signals:
    void dataChanged(const QModelIndex & topLeft, const QModelIndex & bottomRight);

// On the Loop
emit model->dataChanged(model->index(i, 0), model->index(i, 1));

Sorry but this time it also didn't work or I am missing something. Please let me know

Thanks

raven-worx

@Satish-Joshi
you are not doing what i suggested.
Try this:

model = new QStandardItemModel(this);
model->setColumnCount( 2 );
//...
for(int i = 0; i < clusterNames.length(); i++)
{
        QStandardItem *clusterName_i = new QStandardItem(clusterNames[i]);
        QStandardItem *clusterIP_i = new QStandardItem(clusterIPs[i]);
        model->appendRow( QList<QStandardItem*>() << clusterName_i << clusterIP_i );
}

Satish Joshi

@raven-worx

Sorry. It didn't work though

I think there might be some issue with Widget or QSubWindow because as I already mentioned that the values are already updating on the model (checked through debugging it) but couldn't be displayed on the View.

As if I reopen the window it displays properly.

What do you think?

Thanks Anyway

MasterBLB

Use that beginResetModel() and endResetModel() methods then, these makes a model completely invalidated, and therefore force a thorough update.

model->beginResetModel();
for (int i = 0; i < clusterNames.length(); i++)
{
    model->appendRow( { new QStandardItem(clusterNames[i]), new QStandardItem(clusterIPs[i]) } );  
}
model->endResetModel();

Satish Joshi

@MasterBLB

It seems both are protected members so can't access through it.

Thanks

MasterBLB

Inherit QStandardItemModel, and declare public functions like beginReset() and endReset() whose internally invoke these protected methods.