My QSqlQueryModel doesn't show data in the listview

问题

I was playing around with QSqlQueryModel but I am completely stuck right now. I've searched for a solution the entire day but no luck so far.

What I do got working is that it pulls data from my sqlite database BUT for some reason I can not show it in my listview. It looks like my rolenames do not exist.
I get messages like....ReferenceError: id is not defined..... for each row that I pull out of the database.

I've used an example from: http://qt-project.org/wiki/How_to_use_a_QSqlQueryModel_in_QML

I've tried both examples but I always get the same problem.
My ccp file looks like this...

#include "artistssqlmodel.h"

const char* ArtistsSqlModel::COLUMN_NAMES[] = {
    "id",
    "word",
    NULL
};

const char* ArtistsSqlModel::SQL_SELECT = "SELECT id, word FROM dictionary LIMIT 5";

ArtistsSqlModel::ArtistsSqlModel(QObject *parent) :
    QSqlQueryModel(parent)
{
    mydb=QSqlDatabase::addDatabase("QSQLITE");
    QString dbPath = "E://mydb.db";
    mydb.setDatabaseName(dbPath);
    connectToDb();

    int idx = 0;
    QHash<int, QByteArray> roleNames;
    while( COLUMN_NAMES[idx]) {
        roleNames[Qt::UserRole + idx + 1] = COLUMN_NAMES[idx];
        idx++;
    }
    //roleNames(roleNames);
    refresh();
}

void ArtistsSqlModel::connectToDb()
{
    //QString bla = "Default";

    if(!mydb.open())
    {
        qDebug() << "Database didnt open";
    }
    else
    {
        qDebug() << "Your database is open";
    }
}

void ArtistsSqlModel::refresh()
{
    this->setQuery(SQL_SELECT);
}

QVariant ArtistsSqlModel::data(const QModelIndex &index, int role) const
{
    QVariant value = QSqlQueryModel::data(index, role);
    if(role < Qt::UserRole)
    {
        value = QSqlQueryModel::data(index, role);
    }
    else
    {
        int columnIdx = role - Qt::UserRole - 1;
        QModelIndex modelIndex = this->index(index.row(), columnIdx);
        value = QSqlQueryModel::data(modelIndex, Qt::DisplayRole);
    }
    return value;
}

and my qml file looks like this

import QtQuick 2.2
import QtQuick.Window 2.1

Window {
    visible: true
    width: 800
    height: 800

    ListView{
        anchors.fill:parent
        model:artistsModel
        delegate: Item{
            width:parent.width
            height: width/10
            Text {
                id: name
                text: word
                verticalAlignment: Text.AlignVCenter
                horizontalAlignment: Text.AlignHCenter
                anchors.fill:parent
            }
        }
    }
}

I hope I provided enough info and I hope somebody knows what I am doing wrong. I'm new with qt and c++ but normally I can solve the issues with some research.
This time I am completely stuck and I need to figure out a way to get the data from my sqlite db into my listsviews.

EDIT: Thanks for the reply here is all the rest of the code (these are the files I've got) The artistssqlmodel.h file

#ifndef ARTISTSSQLMODEL_H
#define ARTISTSSQLMODEL_H

#include <QObject>
#include <QSqlQueryModel>
#include <QDebug>

class ArtistsSqlModel : public QSqlQueryModel
{
    Q_OBJECT
public:
    explicit ArtistsSqlModel(QObject *parent);
    void refresh();
    QVariant data(const QModelIndex &index, int role) const;
    void connectToDb();
signals:
public slots:
private:
    const static char* COLUMN_NAMES[];
    const static char* SQL_SELECT;
    QSqlDatabase mydb;
};


#endif // ARTISTSSQLMODEL_H

and the main.cpp

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QtQml>
#include "artistssqlmodel.h"

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);
    QQmlApplicationEngine engine;

    QQmlContext *context = engine.rootContext();
    ArtistsSqlModel *artistsSqlModel = new ArtistsSqlModel( qApp);

    context->setContextProperty("artistsModel", artistsSqlModel);
    engine.load(QUrl(QStringLiteral("qrc:///qml/main.qml")));

    return app.exec();
}

回答1:

It looks like my rolenames do not exist

Exactly. You doesn't define the rolenames where QML knows to look for. The wiki where you got the example is out dated. The "new" way to expose the rolenames for a model is reimplementing the QAbstractItemModel::rolenames() method. Move the rolenames definition to it:

QHash<int, QByteArray> ArtistsSqlModel::rolenames() const
{
  int idx = 0;
  QHash<int, QByteArray> roleNames;
  while( COLUMN_NAMES[idx]) {
    roleNames[Qt::UserRole + idx + 1] = COLUMN_NAMES[idx];
    idx++;
  }  
  return roleNames;
}

By the way, I suggest you to use the new Qt documentation, if you are not using yet. I think is much clear and organized than the old one.

I hope this help you.

来源：https://stackoverflow.com/questions/24390921/my-qsqlquerymodel-doesnt-show-data-in-the-listview

标签

c++

qml