如何将 Qt 中的 SQL 查询输出模型分配给 QML 的 TableView？

Posted 2023-02-16

【中文标题】如何将 Qt 中的 SQL 查询输出模型分配给 QML 的 TableView？

【英文标题】：How to assign SQL query output model from Qt to QML's TableView?

【发布时间】：2015-01-08 11:46:18

【问题描述】：

来自 C++ (Qt)：

int main(int argc, char *argv[])

    QApplication app(argc, argv);

    /*
     * I have omitted the code about connection with the database and all for ease of   
     * viewing the code.
     */


    // My own function for filling in the data in the `QSqlQueryModel`
    QSqlQueryModel* model = new QSqlQueryModel;
    QString binid = "B1";
    QString query = "SELECT t1.BinId, t1.PartitionId, t2.UnitId, t2.ItemCount FROM Bin_Partitions AS t1 "
                    "INNER JOIN Partition_Units AS t2 ON t1.PartitionId = t2.PartitionId "
                    "WHERE t1.BinId ='" + binid + "'";
    model->setQuery(query);

    /*
     * I can see that the query runs successfully because the following
     * QTableView DOES get populated properly. 
     */
    // Use QTableView to visualize
    QTableView *view = new QTableView;
    view->setModel(model);
    view->show();

    QQmlApplicationEngine engine;
    // Passing the same model to QML for displaying in the TableView.
    engine.rootContext()->setContextProperty ("SQQL", model);
    engine.load(QUrl(QStringLiteral("/home/.../main.qml")));

    QObject               *topLevel  = engine.rootObjects ().value (0);
    QQuickWindow          *window    = qobject_cast <QQuickWindow *> (topLevel);

    return app.exec();

来自 QML：

import QtQuick 2.2
import QtQuick.Window 2.1
import QtQuick.Controls 1.2

Window

    visible: true
    width: 360
    height: 360
    color: "blue"

    TableView
    
        TableViewColumn role: "col1" ; title: "BinId" ; visible: true
        TableViewColumn role: "col2" ; title: "PartitionId" 
        TableViewColumn role: "col3" ; title: "UnitId" 
        TableViewColumn role: "col4" ; title: "ItemCount" 

        model: SQQL
    

QML的TableView显示为EMPTY！

我需要帮助。

【参考方案1】：

您必须继承 QSqlQueryModel 并重新实现 roleNames 和 data 方法

MySqlModel.h

class mysqlModel: public QSqlQueryModel

    Q_OBJECT
public:
    MySqlModel(QObject *parent = 0) : QSqlQueryModel(parent) 

    enum Roles 
        BinId = Qt::UserRole + 1,
        PartitionId,
        UnitId,
        ItemCount
    ;
    QHash<int, QByteArray> roleNames() const 
        QHash<int, QByteArray> roles;
        roles[BinId] = "binIdRole";
        roles[PartitionId] = "partitionIdRole";
        roles[UnitId] = "unitIdRole";
        roles[ItemCount] = "itemCountRole";
        return roles;
    
    QVariant data(const QModelIndex &index, int role) const 
        if (!index.isValid())
            return QVariant();

        QString fieldName;
        switch (role) 
            case BinId: fieldName = QStringLiteral("t1.BinId"); break;
            case PartitionId: fieldName = QStringLiteral("t1.PartitionId"); break;
            case UnitId: fieldName = QStringLiteral("t2.UnitId"); break;
            case ItemCount: fieldName = QStringLiteral("t2.ItemCount"); break;
        
        if (!this->record().isGenerated(fieldName))
            return QVariant();
        else 
            QModelIndex item = indexInQuery(index);
            if ( !this->query().seek(item.row()) )
                return QVariant();
            return this->query().value(fieldName);
        
        return QVariant();
    
;

ma​​in.qml

Window  
    visible: true
    width: 640
    height: 480
    TableView 
        anchors.fill: parent
        model: SQQL
        TableViewColumn role: "binIdRole" ; title: "BinId" ; visible: true
        TableViewColumn role: "partitionIdRole" ; title: "PartitionId" 
        TableViewColumn role: "unitIdRole" ; title: "UnitId" 
        TableViewColumn role: "itemCountRole" ; title: "ItemCount" 
    

【讨论】：

非常感谢您。我在这里找到了进一步的提示：qt-project.org/wiki/How_to_use_a_QSqlQueryModel_in_QML

@TheIndependentAquarius 链接不再有效。你是怎么解决问题的？

@KernelPanic：链接现在在这里wiki.qt.io/How_to_use_a_QSqlQueryModel_in_QML ...只是为了进一步阅读，我猜。