Question

我的问题是我希望数据库数据加上QComboBox中的默认值。当我使用 QStringList通过每次调用函数我都有重复项。这是updateComboBox函数：

void MainWindow::updCombo(){


QSqlQuery * qry1 = new QSqlQuery(mydb);
qry1->prepare("select DISTINCT  Grp from Poems");
qry1->exec();
QStringList strList;
while(qry1->next()) {

    if(!strList.contains(qry1->value(0).toString()))
    {
        qDebug()<< qry1->value(0).toString();
        strList->append(qry1->value(0).toString());
    }

}

ui->comboBox->addItems(strList);

}

Answer 1

如果要向模型添加元素，可以使用代理，如下所示：

appendproxymodel.h

#ifndef APPENDPROXYMODEL_H
#define APPENDPROXYMODEL_H

#include <QIdentityProxyModel>

class AppendProxyModel: public QIdentityProxyModel{
public:
    using QIdentityProxyModel::QIdentityProxyModel;
    QVariant data(const QModelIndex &index, int role) const;
    int rowCount(const QModelIndex &parent=QModelIndex()) const;
    QModelIndex index(int row, int column, const QModelIndex &parent) const;
    QStringList defaults() const;
    void setDefaults(const QStringList &defaults);
private:
    QStringList mDefaults;
};

#endif // APPENDPROXYMODEL_H

appendproxymodel.cpp

#include "appendproxymodel.h"

QVariant AppendProxyModel::data(const QModelIndex &index, int role) const
{
    if(index.row() >= 0 && index.row() < mDefaults.size() && role==Qt::DisplayRole){
        return mDefaults[index.row()];
    }
    if(index.row() >= mDefaults.size() && index.row() < rowCount()){
        return  QIdentityProxyModel::data(
                    QIdentityProxyModel::index(index.row()-mDefaults.size(), index.column()),
                    role);
    }
    return QIdentityProxyModel::data(index, role);
}

int AppendProxyModel::rowCount(const QModelIndex &parent) const
{
    return  mDefaults.size()+ QIdentityProxyModel::rowCount(parent);
}

QModelIndex AppendProxyModel::index(int row, int column, const QModelIndex &parent) const
{
    if(row < rowCount()- mDefaults.size())
        QIdentityProxyModel::index(row, column, parent);
    return createIndex(row, column);
}

QStringList AppendProxyModel::defaults() const
{
    return mDefaults;
}

void AppendProxyModel::setDefaults(const QStringList &defaults)
{
    mDefaults = defaults;
    emit dataChanged(index(0, 0, QModelIndex()), index(rowCount(),columnCount(), QModelIndex()));
}

示例：

QComboBox combo;
QSqlQueryModel model;
model.setQuery("select DISTINCT firstname from person");
AppendProxyModel proxy;
proxy.setDefaults({"all", "option1", "option2"});
proxy.setSourceModel(&model);
combo.setModel(&proxy);

下面的link中有一个完整的示例

将默认值添加到与QSqlQueryModel绑定的QCombobox

1 个答案: