Binding list from C++ to QML

[TonyN]

I simplified the MainForm.ui.qml (as below) and find that the QML report "TypeError: Cannot read property 'items' of undefined" for each instance of the the page when I execute the app. According to this, I think I have to register Items_model. However I am unable to do so with qmlRegisterType()

(I rename the property Items in Page_model to have lowercamel: Q_PROPERTY(Items_model* items READ Items WRITE setItems NOTIFY itemsChanged) )

import QtQuick 2.4
import QtQuick.Controls 1.3

Rectangle {
    id: rectangleMain
    property alias quitButton: quitButton
    property alias pagesView: pagesView

    width: 360
    height: 360




    ListView {
        id: pagesView
        width: 500
        orientation: ListView.Horizontal
        spacing: 2

        anchors {
            bottom: quitButton.top
            bottomMargin: 8
            right: parent.right
            rightMargin: 0
            left: parent.left
            leftMargin: 0
            top: parent.top
            topMargin: 0
        }

        delegate: Rectangle {
            id:paView
            height: parent.height
            width:100
            color: "transparent"
            border.color: "teal"
            border.width: 1
            radius: 6

            GridView {

                anchors { rightMargin: 6
                    leftMargin: 6
                    bottomMargin: 6
                    topMargin: 6
                    fill: parent
                }
                cellWidth: width / 2
                cellHeight: 50

                model:model.items

                delegate: Rectangle {
                    height: 46
                    width: 46
                    color: "blue" //colorCode
                    Text {

                        anchors.horizontalCenter: parent.horizontalCenter
                        anchors.verticalCenter: parent.verticalCenter
                        text:model.displayText
                    }
                }
            }
        }
    }

    Button {
        id: quitButton
        y: 325
        text: qsTr("Quit")
        anchors {
            right: parent.right
            rightMargin: 50
            left: parent.left
            leftMargin: 50
            bottom: parent.bottom
            bottomMargin: 8
        }
    }
}

[TuanLT]

Thanks you very much!

But, now i have new problem, when i using signal and slot to communicate between cpp file and qml file. I'm using code below:

Cpp file (main.cpp)

QQmlApplicationEngine engine;
QQmlContext* context = engine.rootContext();
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
QObject *topLevel = engine.rootObjects().value(0);
QQuickWindow *window = qobject_cast<QQuickWindow *>(topLevel);
KeywordBusiness business;
QObject::connect(window,SIGNAL(savekeywords(KeywordsModel)), &business, SLOT(SaveChangedData(KeywordsModel)));

on class KeywordBusiness .h I define a slot SaveChangedData with parameter is KeywordsModel extends QObject

On qml file. I define a signal savekeywords with also parameter is KeywordsModel.

But when i click button to call signal savekeywords , in cpp file the QObject::connect funtion not working.

Please help me, I was missing something?

Thanks!

[TonyN]

@TuanLT Dude, I post it for someone to help me to solve my problem. Please post your question in the separate post.

[p3c0]

@TonyN

I simplified the MainForm.ui.qml (as below) and find that the QML report "TypeError: Cannot read property 'items' of undefined" for each instance of the the page when I execute the app.

Since that property is in parent model try accessing it with its parent object.
model: pagesView.model.items

[TonyN]

@p3c0 : Thanks, you are correct about that, but that is not enough to solve the problem. I find out what was missing. Instead, create the Q_PROPERTY, I have to create custom "roles" like these (example code below) in the model. Again, I don't know this is the right way or not, but it solved my problem of binding models further down on the chain (second level). But then now, I find out that the QAbstractTableModel may not the right choice :~) Despite I implemented columnCount(), it only ask for data in rows of column 0!!

QHash<int, QByteArray> Pages_model::roleNames() const
{
    QHash<int, QByteArray> roles;
    roles[DisplayNameRole] = "displayName";
    roles[DisplayItemsRole] = "displayItems";

    return roles;
}

QVariant Pages_model::data(const QModelIndex &index, int role) const
{
    if (!index.isValid())
        return QVariant();

    int i = index.row();
    if (i < 0 || i >= _pagesModelList.count())
        return QVariant();

    const Page_model *pPage = _pagesModelList[i];
    if (role == DisplayNameRole)
    {
        return pPage->displayName();
    }
    else if (role == DisplayItemsRole)
    {
        return QVariant::fromValue(pPage->Items());
    }

    return QVariant();
}

[p3c0]

@TonyN

But then now, I find out that the QAbstractTableModel may not the right choice :~) Despite I implemented columnCount(), it only ask for data in rows of column 0!!

That's right GridView or ListView only deals with rows. In that case can't you replace it with QAbstractItemModel ? Keep everything other than columns.

[TonyN]

@p3c0 Uh but then which view should I use? I read this,
"QAbstractItemModel presents a hierarchy of tables, but the views currently provided by QML can only display list data."
Does that mean, at the present time, nothing I can use except maybe create my own view!? If so, what is the best reading can you recommend?

[TonyN]

@p3c0 I solved the problem! Even without doing custom roles. I just simplified it, adding some qRegisterMetaType. The solution is not as I want to be, but it works. For now, I just have to figure out how to hide the dummy items. Thank you for pointing out some direction.

[p3c0]

@TonyN Congratulations :)
IMO you can use QAbstractItemModel with GridView(for grid like item positioning) or ListView (for list like item positioning). For hiding dummy items you can maintain a field for items and update it from the model whenever required.

[TonyN]

@p3c0 I certainly want to hear other opinion. I did attempt to use QAbstractItemModel, but then the GridView still treat model as a list!?
(my current solution is using QAbstractListModel with GridView, and compute item's index from its specified row and column, if there is no item at the requested index, I just return QVariant(). The rowCount() of QAbstractItemModel is the total item the can represent on the grid (row * column) )

[p3c0]

@TonyN GridView doesnot have the facility to get items using columns. AFAIK your current solution is the only way to go. Btw inside GridView you already have the index attached property.