[solved] Newbie is confused.How to add dynamic data to TableView and parse through it send data to c++

[vishnu]

@p3c0
Okay, Any other way to access the TableView model in C++ side?

[p3c0]

@vishnu AFAIK. no. But that error is not related to TableView or ListModel.

[vishnu]

@p3c0
Got it.The error was due to the wrong import statement in qml.
Now How do I capture the changes?
If reading the entire model is the solution (ofcourse not efficient).
How can I call this public slot getModel when ever there is a change in TableView in qml? What is the signal I get from the model/view which tells me that there is a change ?

void TCPCommunicationPort::getModel(QQmlApplicationEngine &engine)
{
    QObject* root = engine.rootObjects().first(); //get the root object as usual
    QObject* list = root->findChild<QObject*>("setTableView"); //get the ListView

    QVariant qmlmodel = list->property("model"); //access model property of ListView
    QAbstractListModel *model = qvariant_cast<QAbstractListModel *>(qmlmodel); //convert to QAbstractListModel
.....//data is handled here

[p3c0]

@vishnu As we casted it to QAbstractListModel we can connect to its signal dataChanged from C++. Thus when anything changes the slot will be called.

QAbstractListModel *model = qvariant_cast<QAbstractListModel *>(qmlmodel);
QObject::connect(model,SIGNAL(dataChanged(QModelIndex,QModelIndex,QVector<int>)),
                     &myclass,SLOT(onDataChanged(QModelIndex,QModelIndex,QVector<int>)));

Access the changed data in slot

void MyClass::onDataChanged(const QModelIndex &topLeft, 
             const QModelIndex &bottomRight, const QVector<int> &roles)
{
    qDebug() << "Data Changed :" << topLeft.data(roles[0]) << topLeft.data(roles[1]);
}

[vishnu]

@p3c0
I don't know why but the SLOT is not called when the data changes.
I did the connection in main itself.
main.qml

QQmlApplicationEngine engine;
    TCPCommunicationPort tcpCommunicationPort;
    auto root_context = engine.rootContext();
    root_context->setContextProperty("tcpCommunicationPort",&tcpCommunicationPort);
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
//    tcpCommunicationPort.getModel(engine);
    QObject* root = engine.rootObjects().first(); //get the root object as usual
    QObject* list = root->findChild<QObject*>("setTableView"); //get the ListView

    QVariant qmlmodel = list->property("model"); //access model property of ListView
    QAbstractListModel *model = qvariant_cast<QAbstractListModel *>(qmlmodel); //convert to QAbstractListModel

    QObject::connect(model,SIGNAL(dataChanged(QModelIndex,QModelIndex,QVector<int>)),
                         &tcpCommunicationPort,SLOT(onDataChanged(QModelIndex,QModelIndex,QVector<int>)));

In header file

public slots:
void onDataChanged(const QModelIndex &topLeft,
                            const QModelIndex &bottomRight, const QVector<int> &roles);

May i know why the slot is not called?I even don't know whether the signal is raised or not.How to know whether the signal is emitted not in this case?

[p3c0]

@vishnu

May i know why the slot is not called?I even don't know whether the signal is raised or not.How to know whether the signal is emitted not in this case?

Since you are using ListModel use onDataChanged signal handler.

ListModel {
    id: myModel

    onDataChanged: console.log("Data Changed")
}

thus verify whether the data is changed.

[vishnu]

@p3c0
nice hint. unfortunatelly onDataChanged singal is not emitted. when ever I am changing data,adding new row. That means problem is on my QML side.Again this is code for my model,View:
setTable.qml

import QtQuick 2.3
import QtQuick.Window 2.2
import QtQuick.Controls 1.3
import QtQuick.Layouts 1.1
Rectangle {
    id:root
    anchors.fill: parent
    Row{
        id:buttons
        anchors.top: root.top
        Button{
            id:addNewRowButton
            text: "ADD"
            onClicked: {
                setTableModel.append({x_position: 0,
                                         y_position:0,
                                         z_position:0,
                                         velocity :0,
                                         acceleration:0,
                                         deceleration:0,
                                         tool:0,
                                         tracking_x:0,
                                         tracking_y:0,
                                         tracking_z:0}
                                     )
            }
        }
        Button{
            id:deleteRowButton
            text: "DELETE"
            onClicked: {
                setTableModel.remove(setTableView.currentRow)
            }
        }

    }
    ListModel{
        id:setTableModel

        ListElement{
            x_position: 0
            y_position: 300
            z_position: 500
            velocity: 100
            acceleration:100
            deceleration:0
            tool:0
            tracking_x: 0
            tracking_y:0
            tracking_z:0
        }
        onDataChanged: {
            console.log("Data changed")
        }
    }

    TableView{
        id:setTableView
        objectName: "setTableView"
        model: setTableModel
        width: parent.width
        height: parent.height-buttons.height
        Layout.minimumWidth: 400
        Layout.minimumHeight: 240
        Layout.preferredWidth: 600
        Layout.preferredHeight: 400
        anchors.top: buttons.bottom
        TableViewColumn {
            role: "x_position"
            title: "X mm"
            width: 80
        }
        TableViewColumn {
            role: "y_position"
            title: "Y mm"
            width: 80
        }
        TableViewColumn {
            role: "z_position"
            title: "Z mm"
            width: 80
        }
        TableViewColumn {
            role: "velocity"
            title: "V m/s"
            width: 80
        }
        TableViewColumn {
            role: "acceleration"
            title: "A m/s2"
            width: 80
        }
        TableViewColumn {
            role: "deceleration"
            title: "D m/s2"
            width: 80
        }
        TableViewColumn {
            role: "tool"
            title: "Tool"
            width: 80
            delegate:
                TextInput {
                anchors.left: parent.left
                anchors.verticalCenter: parent.verticalCenter
                renderType: Text.NativeRendering
                validator: IntValidator {bottom: 0; top: 1;}
                text: styleData.value
            }
        }
        TableViewColumn {
            role: "tracking_x"
            title: "Tx mm"
            width: 80
        }
        TableViewColumn {
            role: "tracking_y"
            title: "Ty mm"
            width: 80
        }
        TableViewColumn {
            role: "tracking_z"
            title: "Tz mm"
            width: 80
        }
        itemDelegate: Item {
            TextInput {
                anchors.left: parent.left
                anchors.verticalCenter: parent.verticalCenter
                renderType: Text.NativeRendering
                text: styleData.value
            }
        }
    }
}

[p3c0]

@vishnu AFAICS You are just adding and removing the data but not updating it. In this case dataChanged wont be called.

[vishnu]

@p3c0
Any hint or example on how to update the data? Thanks a lot

[p3c0]

@vishnu Make use rowsInserted of rowsRemoved signals. Connect them to their respective slots as shown previously for dataChanged.

[vishnu]

@p3c0
I have already added 3 rows with default value. when ever I change default value to someother value. I am not getting the updated value to c++ side.
QObject::connect(model,SIGNAL(dataChanged(QModelIndex,QModelIndex,QVector<int>)), &myclass,SLOT(onDataChanged(QModelIndex,QModelIndex,QVector<int>)));
This is not working? As you said since I am not updating the model, just appending and removing the rows.I feel like there has to be done more in my QML part.May I know what is wrong or missing in my Model and View (QML) ?Thanks

[p3c0]

@vishnu

I have already added 3 rows with default value. when ever I change default value to someother value. I am not getting the updated value to c++ side.

how are you changing the default value ?

[vishnu]

@p3c0
I can change my default values because my delegate is a TextInput.

 TableViewColumn {
            role: "tool"
            title: "Tool"
            width: 80
            delegate:
                TextInput {
                anchors.left: parent.left
                anchors.verticalCenter: parent.verticalCenter
                renderType: Text.NativeRendering
                validator: IntValidator {bottom: 0; top: 1;}
                text: styleData.value
            }
        }

[p3c0]

@vishnu Im asking how do you change the items added in ListModel ? That signal will only be updated only when you update the existing items in the model.
For eg:

ListModel {
    id: myModel

    ListElement {
        name: "abc"
        age: 12
    }

    onDataChanged: console.log("Changed")
}

//updating the list model
myModel.set(0, { "name" : "xyz" } )

So here the signal dataChanged will be triggered and hence the slot onDataChanged in QML will be invoked. Same will work for C++ slot too.

Now in your earlier code you are just adding and removing the rows so those signals (mentioned earlier) will be triggered.

[vishnu]

@p3c0
I am no where doing that kind of updating. I am assuming that ListModel.append method does updating the model as well as view.

Button{
                id:addNewRowButton
                text: "ADD"
                onClicked: {
                    setTableModel.append({"x_position": 0,
                                             "y_position":0,
                                             "z_position":0,
                                             "velocity":0,
                                             "acceleration":0,
                                             "deceleration":0,
                                             "tool":0,
                                             "tracking_x":0,
                                             "tracking_y":0,
                                             "tracking_z":0}
                                         )
                }
            }

[p3c0]

@vishnu No that is not updating. That wont invoke the data changed signal.
As said earlier if you use append or remove use rowsInserted or rowsRemoved signals repectively.

[vishnu]

@p3c0
you are right. This works perfect. I can see the data in c++ when ever a new row is added.

 QObject::connect(model,SIGNAL(rowsInserted(QModelIndex,int,int)),
                         &tcpCommunicationPort,SLOT(onRowsInserted(QModelIndex,int,int)));

But when one of item in the Row is changed I can't see the new data in c++.So that means only Set/setproperty of ListModel will invoke the data changed signal. That mean My qml code is wrong if i want dataChangedsignal.
I changed my TableView like this:

TableView{
            id:setTableView
            objectName: "setTableView"
            model: {
                 setTableModel.set(0,{"x_position": 0,
                                       "y_position":300,
                                       "z_position":500,
                                       "velocity":0,
                                       "acceleration":0,
                                       "deceleration":0,
                                       "tool":0,
                                       "tracking_x":0,
                                       "tracking_y":0,
                                       "tracking_z":0});
                setTableModel.set(1,{"x_position": 0,
                                      "y_position":400,
                                      "z_position":800,
                                      "velocity":0,
                                      "acceleration":0,
                                      "deceleration":0,
                                      "tool":0,
                                      "tracking_x":0,
                                      "tracking_y":0,
                                      "tracking_z":0})
            }

Now the entire view if gone. I cannot add anymore rows.That means what I have done is wrong.But don't know what to do.
Also If the user changes some value in any of the times.how can i know which value is changed? TableView has onClicked signal I can get the current row ,and delegate has access to the properties styleData.row - the index of the row ; styleData.column - the index of the column. Don't know how to make use of them.
Can you please tell me what exactly have to be done on my QML side. Should i change my delegate or View or Model code?Thanks.

[p3c0]

@vishnu Keep your code with append and remove as it is. It just adds and removes the rows. Now to update the already added elements in ListModel use set.
So,

append -> rowsInserted
remove -> rowsRemoved
update i.e set -> dataChanged

[vishnu]

@p3c0
I got the meaning what your saying but Where and how exactly I should do that set.
For eg: should I do like this

Button{
                id:addNewRowButton
                text: "ADD"
                onClicked: {
                    setTableModel.append({"x_position": 0,
                                             "y_position":0,
                                             "z_position":0,
                                             "velocity":0,
                                             "acceleration":0,
                                             "deceleration":0,
                                             "tool":0,
                                             "tracking_x":0,
                                             "tracking_y":0,
                                             "tracking_z":0}
                                         )
//ofcourse index is not defined, May be I make a property and increment it when even I add new row.
                    setTableModel.set(index,{"x_position": 0,
                                          "y_position":0,
                                          "z_position":0,
                                          "velocity":0,
                                          "acceleration":0,
                                          "deceleration":0,
                                          "tool":0,
                                          "tracking_x":0,
                                          "tracking_y":0,
                                          "tracking_z":0})
                }

How about defalut values where should i set them?
Is It in Tableview:this went totally wrong.

id:setTableView
            objectName: "setTableView"
            model: {
                 setTableModel.set(0,{"x_position": 0,
                                       "y_position":300,
                                       "z_position":500,
                                       "velocity":0,
                                       "acceleration":0,
                                       "deceleration":0,
                                       "tool":0,
                                       "tracking_x":0,
                                       "tracking_y":0,
                                       "tracking_z":0});

[p3c0]

@vishnu See

• set is used to update the ListModel
• since you have used TextInput to allow user to update the data you need a way to update the model from this. This can be done in onAccepted handler of TextInput
  So to sum up, for eg:

delegate: TextInput {
    anchors.fill: parent
    text: styleData.value
    onAccepted: {
        myModel.set( styleData.row, { title: text } ) //updates the role name "title" with updated text of TextInput
    }
}