c++ - 扩展 QStandardItem 不返回数据

Question

我有一个自定义类 ConnectionStandardItem，它是 QStandardItem 的子类。此项应包含稍后在 QSqlDatabase 中使用的服务器、用户名、密码等信息。

ConnectionStandardItem::ConnectionStandardItem(QString const& connectionId) : QStandardItem()
{  
    QMap<QString, QVariant>  m_connectionDefinition;
    QSettings settings(QSettings::IniFormat, QSettings::UserScope, "goat", "connections");

    if (!connectionId.isEmpty())
    {
        settings.beginGroup(connectionId.trimmed());

        m_connectionDefinition[connectionId] = QVariant(connectionId.trimmed());

        foreach(QString key, settings.childKeys())
        {
            m_connectionDefinition[key] = settings.value(key);
        }

        setText(m_connectionDefinition["name"].toString());
        setData(m_connectionDefinition, Qt::UserRole);

        settings.endGroup();
    }
}

在对话框中使用扩展的 QStandardItem:

NewConnectionDialog::NewConnectionDialog(QWidget *parent) : QDialog(parent), ui(new Ui::NewConnectionDialog) {
    ui->setupUi(this);

    m_model = new QStandardItemModel(this);
    m_driversModel = new QStandardItemModel(this);
    m_connectionListModel = new QStandardItemModel(this);

    ui->listDropdownDBDriver->setModel(m_driversModel);
    ui->listViewConnections->setModel(m_connectionListModel);

    /* set combobox */
    QStandardItem* item_psql = new QStandardItem();
    item_psql->setText("PostgreSQL");
    item_psql->setData("QPSQL", Qt::UserRole);
    m_driversModel->appendRow(item_psql);

    QStandardItem* item_mysql = new QStandardItem();
    item_mysql->setText("MySQL/MariaDB");
    item_mysql->setData("QMYSQL", Qt::UserRole);
    m_driversModel->appendRow(item_mysql);

    updateConnectionListModel();

    connect(ui->listViewConnections->selectionModel(), SIGNAL(selectionChanged(QItemSelection, QItemSelection)), this, SLOT(handleSelectionChanged(QItemSelection, QItemSelection)));
    connect(m_connectionListModel, SIGNAL(itemChanged(QStandardItem*)), this, SLOT(updateListViewItem(QStandardItem*)));
}

void NewConnectionDialog::handleSelectionChanged(QItemSelection current, QItemSelection previous) {
    const QModelIndex index = ui->listViewConnections->currentIndex();
    ConnectionStandardItem* connection = m_connectionListModel->itemFromIndex(index)->data().value<ConnectionStandardItem*>();


    QMap<QString, QVariant> connectionDefinition = connection->data().value<QMap<QString, QVariant>>();

    //ui->listDropdownDBDriver->setCurrentIndex(index);
    ui->txtUser->setText(connectionDefinition["username"].toString());
    ui->txtPass->setText(connectionDefinition["pass"].toString());
    ui->txtServer->setText(connectionDefinition["server"].toString());
    ui->txtPort->setText(connectionDefinition["port"].toString());
    ui->txtDatabase->setText(connectionDefinition["database"].toString());
}

void NewConnectionDialog::updateConnectionListModel() {
    QSettings settings(QSettings::IniFormat, QSettings::UserScope, "goat", "connections");

    foreach(QString key, settings.childGroups())
    {
        ConnectionStandardItem* item = new ConnectionStandardItem(key);
        m_connectionListModel->appendRow(item);
    }
}

不幸的是，在对话框中，我无法访问当前所选项目的数据。我检查的方法是 handleSelectionChanged。

我如何从 ConnenctionStandardItem 中正确提取 Map 对象，以便更新 GUI，反之亦然，将 gui 中的更改发送回模型(并通过模型发送到 .ini 设置文件)？有没有更好的方法来解决这个问题(不同组织的类(class))？

Answer 1

ConnectionStandardItem 不是保存在QStandardItem 中的数据，但您必须从QStandardItem 中转换ConnectionStandardItem。

另一方面，您将数据保存在 Qt::UserRole 角色中:

setData(m_connectionDefinition, Qt::UserRole);

但是当使用 data() 时根据文档，您正在使用 Qt::UserRole + 1 角色:

QVariant QStandardItem::data(int role = Qt::UserRole + 1) const

解决方案如下:

void NewConnectionDialog::handleSelectionChanged(QItemSelection current, QItemSelection previous) {
    const QModelIndex index = ui->listViewConnections->currentIndex();

    QStandardItem *item = m_connectionListModel->itemFromIndex(index);
    ConnectionStandardItem* connection  = static_cast<ConnectionStandardItem*>(item); // <---    
    QMap<QString, QVariant> connectionDefinition = connection->data(Qt::UserRole).value<QMap<QString, QVariant>>(); // <---

    //ui->listDropdownDBDriver->setCurrentIndex(index);
    ui->txtUser->setText(connectionDefinition["username"].toString());
    ui->txtPass->setText(connectionDefinition["pass"].toString());
    ui->txtServer->setText(connectionDefinition["server"].toString());
    ui->txtPort->setText(connectionDefinition["port"].toString());
    ui->txtDatabase->setText(connectionDefinition["database"].toString());
}

尽管我看到转换也不是必需的，因为我们不打算使用 ConnectionStandardItem 中实现的方法，所以我们只能使用 QStandardItem:

void NewConnectionDialog::handleSelectionChanged(QItemSelection current, QItemSelection previous) {
    const QModelIndex index = ui->listViewConnections->currentIndex();

    QStandardItem *connection = m_connectionListModel->itemFromIndex(index);   
    QMap<QString, QVariant> connectionDefinition = connection->data(Qt::UserRole).value<QMap<QString, QVariant>>(); // <---

    //ui->listDropdownDBDriver->setCurrentIndex(index);
    ui->txtUser->setText(connectionDefinition["username"].toString());
    ui->txtPass->setText(connectionDefinition["pass"].toString());
    ui->txtServer->setText(connectionDefinition["server"].toString());
    ui->txtPort->setText(connectionDefinition["port"].toString());
    ui->txtDatabase->setText(connectionDefinition["database"].toString());
}