Gridview dynamic update on C++ model setData() or qml ListModel set()

[fabur]

Hi all,

I'm having problems understanding why this is not working, I just want to have an item in the view dynamically updated when I change the data in the model using the ListModel method set() , I've also used a C++ model and setData() which emits dataChanged() signal but I can't see any refresh though. I'm stucked.

import QtQuick 2.5
import QtQuick.Controls 2.2
import QtQuick.Layouts 1.2


Dialog {
    id: mydialog
    anchors.centerIn: parent
    width: parent.width / 2
    height: parent.height / 2
    padding: 32
    modal: true

    ListModel {
        id: theModel

        ListElement { number: 0 }
        ListElement { number: 1 }
        ListElement { number: 2 }
        ListElement { number: 3 }
        ListElement { number: 4 }
        ListElement { number: 5 }
        ListElement { number: 6 }
        ListElement { number: 7 }
        ListElement { number: 8 }
        ListElement { number: 9 }
    }

    ColumnLayout {
        anchors.fill: parent

        property int count: 9

        Button {
            Layout.alignment: Qt.AlignTop
            Layout.preferredHeight: 20
            Layout.preferredWidth : 50

            text: qsTr("add")

            onClicked: {
                console.debug("add element")
                theModel.append({"number": ++parent.count});
            }

        }

        Button {
            Layout.alignment: Qt.AlignCenter
            Layout.preferredHeight: 20
            Layout.preferredWidth : 50

            text: qsTr("set")

            onClicked: {
                console.debug("set")
                theModel.set(0, {"number": 12});
            }

        }

        GridView {
            Layout.alignment: Qt.AlignBottom
            id: view
            Layout.preferredHeight: 100
            Layout.preferredWidth : 400
            //anchors.margins: 20

            clip: true

            model: theModel

            cellWidth: 45
            cellHeight: 45

            delegate: numberDelegate
        }

        Component {
            id: numberDelegate

            Label {
                width: 400
                height: 40
                text: index
            }
        }

    }
}

follows a second attempt which is more my real case ( I have a custom C++ model ) registered in My.Models 1.0 -> MyModel . It's bit better as I'm able to change the values in the view but the view items are not refreshed until I scroll up or down. Using grid.forceLayout() didn't solve, the only solution I've found is to set grid.model = 0 and reset the model with grid.model = mymodel . I expect this to work without any special trick. here is the code ( I've stripped it lot of lines so maybe the syntax is not correct, hope it's enough ):

import QtQuick 2.12
import QtQuick.Controls 2.5
import QtQuick.Layouts 1.3
import QtQuick.Controls.Material 2.3

import My.Models 1.0

Dialog {
    id: root

    anchors.centerIn: parent
    width: 1000
    height: 700
    padding: 32
    modal: true

    Connections {
        target: MyClass
        // MyClass emit this signal
        onFinishedParsing: {
            // this is an example trying to set all model data to "0.2" , in a real case this data come from MyClass
            for (var i = 0; i < mymodel.rowCount(); i++) {
                mymodel.setData(mymodel.index(i, 0),"0.2",MyModelModel.Value)
                }
    }
    
    ColumnLayout {
        anchors.fill: parent
        spacing: 16

       GridView {
            id: grid
            Layout.fillHeight: true
            Layout.fillWidth: true
            contentWidth: width
            cellWidth: width / 4
            cellHeight: 80
            clip: true

            model: MyModel {
                id: mymodel
                }

            delegate: Label {
                text: model.value
            }
        }
}

the setData method in MyModel is:

bool SimplsModel::setData(const QModelIndex &index, const QVariant &value,
                          int role) {
  if (index.isValid() && role == SimplsModel::Roles::Value) {
    m_rowData[index.row()].value = value.toFloat();
    emit dataChanged(index, index, {SimplsModel::Roles::Value});
    return true;
  }
  return false;
}

I'm really stucked , can't see what's wrong. any help would be really appreciated. thanks.

[qyvlik]

Here is my code which use the QAbstractListModel: TestModel

When change the data, try call beginResetModel and endResetModel .

void TestModel::addDao(const QString &name, int age)
{
    beginResetModel();
    m_datas.append(Dao(name, age));
    endResetModel();
}

[6thC]

When change the data, try call beginResetModel and endResetModel.

Don't (I wouldn't anyhow) do that, that's a big hammer. I do use that but only for a whole set of data.
For an simple append ~not really right.

setData & emit dataChanged is correct.

When reimplementing the setData() function, this signal must be emitted explicitly.

I emit that the whole row changed with mine (see the first 2 args below), but I'm not sure even this is fully optimal. It does work for me - just working is enough for me atm and I'd like to get time to experiment restricting to a unique.

  emit QAbstractTableModel::dataChanged(QAbstractTableModel::index(intOfIter, 0), QAbstractTableModel::index(intOfIter, columnCount()-1), QVector<int>() << role);

I'm still getting my head around trying to get setData actually working from QML side with custom roles, from Table view but this works from Cpp backend, I'm trying to get a complex control sorted that can handle updates with dynamic delegates from QML.

Hopefully this is just enough to get you across the line and moving again too.

[fabur]

@qyvlik

beginResetModel() / endResetModel()

works but actually is a lot of overhead in in setData, I think it's ok if I want to upadate the whole model data in one shot , thanks

@6thC

I've tried this but it didn't solve, as before it do set the data but the view doesn't refresh de delagates, maybe I didn't realize how to apply it for a QAbstractListModel:

emit QAbstractListModel::dataChanged(QAbstractListModel::index(index.row()), QAbstractListModel::index(index.row()), QVector<int>() << SimplsModel::Roles::Value); 

or 

emit QAbstractListModel::dataChanged(QAbstractListModel::index(index.row()), QAbstractListModel::index(index.row()), QVector<int>() << Qt::DisplayRole);

Strange that we have to fight to make this work, I can't find code examples about people achieving this, Am I doing something unusual ? ( I wander )

thanks

[Compozitor]

Try calling a signal without the last parameter.

emit dataChanged(index, index);

[Bob64]

If I understood correctly, it wasn't even working for a QML ListModel. I think that would need to be resolved first before getting bogged down with the C++ model.