QStandardItemModel :: findItems不在QModelIndex（row，col，QModel（row，col））中搜索

Question

I'm trying to create hierarchical tree from sql database. Tree nodes can have the same name, but unique ID. Therefore I search for a node parent by its ID, recognize its index and insert a new child row.

Also I know how QModelIndex es are represented in QTreeView .

Example pic

But I'm stuck in QStandardItemModel::findItems . It searches only in QModelIndex(row, col) , but never in QModelIndex(row, col, QModel(row,col)) .
I would appreciate any advice how to find second column in hierarchical tree model.

Here is my minimum code: main.cpp

#include <QApplication>
#include <QSqlDatabase>
#include <QSqlQuery>
#include <QTreeView>
#include <QStandardItemModel>

void createDB()
{
    QSqlDatabase m_db = QSqlDatabase::addDatabase("QSQLITE");
    m_db.setDatabaseName(":memory:");
    if (!m_db.open()) {
        return;
    }
    QSqlQuery query;
    query.exec("CREATE TABLE IF NOT EXISTS tags ("
               "id INTEGER PRIMARY KEY AUTOINCREMENT,"
               "parent_id INTEGER DEFAULT -1 REFERENCES tags(id),"
               "title TEXT NOT NULL);");
    query.exec("INSERT INTO tags(title) VALUES('item 1');");
    query.exec("INSERT INTO tags(title) VALUES('item 2');");
    query.exec("INSERT INTO tags(parent_id, title) VALUES(1, 'sub 1');");
    query.exec("INSERT INTO tags(parent_id, title) VALUES(2, 'sub 1');");
    query.exec("INSERT INTO tags(parent_id, title) VALUES(2, 'sub 2');");
    query.exec("INSERT INTO tags(parent_id, title) VALUES(3, 'sub sub 1');");
    query.exec("INSERT INTO tags(parent_id, title) VALUES(3, 'sub sub 2');");
}

void createTreeView() {
    QTreeView *m_view = new QTreeView;
    QStandardItemModel *m_model = new QStandardItemModel;
    m_model->setColumnCount(2);
    m_view->setModel(m_model);

    QSqlQuery query("SELECT id, parent_id, title FROM tags;");
    while (query.next()) {
        QList<QStandardItem *> node;
        node << new QStandardItem(query.value("title").toString());
        node << new QStandardItem(query.value("id").toString());
        if (query.value("parent_id").toInt() == -1) {
            m_model->appendRow(node);
        } else {
            QList<QStandardItem *> items = m_model->findItems(query.value("parent_id").toString(), Qt::MatchExactly | Qt::MatchRecursive, 1);
            for (QStandardItem *item : items) {
                QModelIndex index = item->index().siblingAtColumn(0);
                item = m_model->itemFromIndex(index);
                item->appendRow(node);
            }
        }
    }

    m_view->expandAll();
    m_view->resizeColumnToContents(0);
    //m_view->hideColumn(1);
    m_model->setHeaderData(0, Qt::Horizontal, QVariant());
    m_view->show();
}

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    createDB();
    createTreeView();
    return a.exec();
}

What I want to get:

> item 1
    > sub 1
        sub sub 1    // does not appear, because `findItems` returns an empty list.
        sub sub 2    // same
> item 2
    sub 1
    sub 2

I have Qt 5.12.1, MSVC 2017 32bit.

Answer 1

You didn't use the correct "second" parameter of the function "StandardItemModel::findItems". The default scan depth of the function is 1 layer. So, if you want to seek recusively, you should use the parameter "Qt::MatchRecursive".It like:

modelname.findItems("xxxx",  Qt::MatchRecursive);