Problem with TreeView

**init2null** · 23rd May 2008, 02:18

Hello all,

I've been trying for hours to get this QTreeView / QAbstractItemModel code snippet to work with Qt4.4 and VC++ 2008 Express. When I expand the nested items twice, Qt fails with the assert "ASSERT: "i > -1" in file itemviews\qtreeview.cpp, line 3013". Am I doing something wrong?

Qt Code:

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#include <QtGui>
class TestModel;
 
class SceneTest : public QDialog {
public:
    SceneTest();
protected:
    QTreeView *tree;
    TestModel *model;
};
 
class InternalItem {
public:
    InternalItem() {
        parent = NULL;
    }
    ~InternalItem() {qDeleteAll(children);}
    int row() {
        if (parent) {
            return parent->children.indexOf(this);
        } else {
            return 0;
        }
    }
    InternalItem *append(InternalItem *iitem) {children.append(iitem); return (iitem->parent = this);}
    InternalItem *parent;
    QList < InternalItem * > children;
};
 
class TestModel : public QAbstractItemModel {
public:
    TestModel();
    QVariant data(const QModelIndex &index, int role) const;
    Qt::ItemFlags flags(const QModelIndex &index) const;
    QVariant headerData(int section, Qt::Orientation orientation, int role = Qt::DisplayRole) const;
    int rowCount(const QModelIndex &parent = QModelIndex()) const;
    int columnCount(const QModelIndex &parent) const;
    QModelIndex index(int row, int column, const QModelIndex &parent = QModelIndex()) const;
    QModelIndex parent(const QModelIndex &) const;
protected:
    InternalItem *root;
};
 
TestModel::TestModel() {
    root = new InternalItem();
    root->append(new InternalItem());
    root->append(new InternalItem());
    root->children[1]->append(new InternalItem());
    root->children[1]->children[0]->append(new InternalItem());
    root->children[1]->children[0]->children[0]->append(new InternalItem());
}
 
Qt::ItemFlags TestModel::flags(const QModelIndex &index) const {
    return index.isValid() ? (Qt::ItemIsEnabled | Qt::ItemIsSelectable) : 0;
}
 
QVariant TestModel::data(const QModelIndex &index, int role) const {
    if (!index.isValid() || index.column() >= 1)
        return QVariant();
    if (role == Qt::DisplayRole) {
        InternalItem *iitem = static_cast < InternalItem * >(index.internalPointer());
        if (index.column() == 0) {
            return (long)iitem;
        }
    }
    return QVariant();
}
 
QModelIndex TestModel::index(int row, int column, const QModelIndex &parent) const {
    if (!hasIndex(row, column, parent)) {
        return QModelIndex();
    }
    InternalItem *parentItem = NULL;
    if (!parent.isValid()) {
        parentItem = root;
    } else {
        parentItem = static_cast<InternalItem*>(parent.internalPointer());
    }
    InternalItem *child = parentItem->children[row];
    if (child) {
        return createIndex(row, column, child);
    } else {
        return QModelIndex();
    }
}
 
QModelIndex TestModel::parent(const QModelIndex &index) const {
    if (!index.isValid()) return QModelIndex();
    InternalItem *iindex = static_cast < InternalItem * >(index.internalPointer());
    if (!iindex->parent || iindex->parent == root) {
        return QModelIndex();
    }  else {
        return createIndex(iindex->row(), 0, iindex->parent);
    }
}
 
QVariant TestModel::headerData(int section, Qt::Orientation orientation, int role) const {
    if (section == 0 && role == Qt::DisplayRole) {
        return QString("A");
    } else {
        return QVariant();
    }
}
 
int TestModel::rowCount(const QModelIndex &parent) const {
    if (parent.column() > 0) return 0;
    if (parent.isValid()) {
        return static_cast < InternalItem * >(parent.internalPointer())->children.size();
    } else {
        return root->children.size();
    }
}
 
int TestModel::columnCount(const QModelIndex &parent) const {
    return 1;
}
 
SceneTest::SceneTest() : QDialog(NULL) {
    model = new TestModel();
    tree = new QTreeView(this);
    tree->setModel(model);
    QBoxLayout *layout = new QHBoxLayout(this);
    layout->addWidget(tree);
}

#include <QtGui>
class TestModel;

class SceneTest : public QDialog {
public:
    SceneTest();
protected:
    QTreeView *tree;
    TestModel *model;
};

class InternalItem {
public:
    InternalItem() {
        parent = NULL;
    }
    ~InternalItem() {qDeleteAll(children);}
    int row() {
        if (parent) {
            return parent->children.indexOf(this);
        } else {
            return 0;
        }
    }
    InternalItem *append(InternalItem *iitem) {children.append(iitem); return (iitem->parent = this);}
    InternalItem *parent;
    QList < InternalItem * > children;
};

class TestModel : public QAbstractItemModel {
public:
    TestModel();
    QVariant data(const QModelIndex &index, int role) const;
    Qt::ItemFlags flags(const QModelIndex &index) const;
    QVariant headerData(int section, Qt::Orientation orientation, int role = Qt::DisplayRole) const;
    int rowCount(const QModelIndex &parent = QModelIndex()) const;
    int columnCount(const QModelIndex &parent) const;
    QModelIndex index(int row, int column, const QModelIndex &parent = QModelIndex()) const;
    QModelIndex parent(const QModelIndex &) const;
protected:
    InternalItem *root;
};

TestModel::TestModel() {
    root = new InternalItem();
    root->append(new InternalItem());
    root->append(new InternalItem());
    root->children[1]->append(new InternalItem());
    root->children[1]->children[0]->append(new InternalItem());
    root->children[1]->children[0]->children[0]->append(new InternalItem());
}

Qt::ItemFlags TestModel::flags(const QModelIndex &index) const {
    return index.isValid() ? (Qt::ItemIsEnabled | Qt::ItemIsSelectable) : 0;
}

QVariant TestModel::data(const QModelIndex &index, int role) const {
    if (!index.isValid() || index.column() >= 1)
        return QVariant();
    if (role == Qt::DisplayRole) {
        InternalItem *iitem = static_cast < InternalItem * >(index.internalPointer());
        if (index.column() == 0) {
            return (long)iitem;
        }
    }
    return QVariant();
}

QModelIndex TestModel::index(int row, int column, const QModelIndex &parent) const {
    if (!hasIndex(row, column, parent)) {
        return QModelIndex();
    }
    InternalItem *parentItem = NULL;
    if (!parent.isValid()) {
        parentItem = root;
    } else {
        parentItem = static_cast<InternalItem*>(parent.internalPointer());
    }
    InternalItem *child = parentItem->children[row];
    if (child) {
        return createIndex(row, column, child);
    } else {
        return QModelIndex();
    }
}

QModelIndex TestModel::parent(const QModelIndex &index) const {
    if (!index.isValid()) return QModelIndex();
    InternalItem *iindex = static_cast < InternalItem * >(index.internalPointer());
    if (!iindex->parent || iindex->parent == root) {
        return QModelIndex();
    }  else {
        return createIndex(iindex->row(), 0, iindex->parent);
    }
}

QVariant TestModel::headerData(int section, Qt::Orientation orientation, int role) const {
    if (section == 0 && role == Qt::DisplayRole) {
        return QString("A");
    } else {
        return QVariant();
    }
}

int TestModel::rowCount(const QModelIndex &parent) const {
    if (parent.column() > 0) return 0;
    if (parent.isValid()) {
        return static_cast < InternalItem * >(parent.internalPointer())->children.size();
    } else {
        return root->children.size();
    }
}

int TestModel::columnCount(const QModelIndex &parent) const {
    return 1;
}

SceneTest::SceneTest() : QDialog(NULL) {
    model = new TestModel();
    tree = new QTreeView(this);
    tree->setModel(model);
    QBoxLayout *layout = new QHBoxLayout(this);
    layout->addWidget(tree);
}

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**patrik08** · 23rd May 2008, 15:24

Have a look on:
http://www.qtcentre.org/forum/f-qt-p...view-4182.html

**MarkoSan** · 23rd May 2008, 15:45

Did you forget to setup Q_OBJECT macro in your classes?

**init2null** · 23rd May 2008, 17:46

Markosan, I guess it's better to use Q_OBJECT on the model, but since I wasn't using signals yet, it wasn't really necessary. In any case, I tried it and received the same result.

**init2null** · 23rd May 2008, 17:59

Hello Patrik, I'm not entirely sure how that post applies, since I really want to use the current design. I'm not really interested in editing either. My design is based on Qt's simpletreemodel example, so I know that I'm not too far away from working code.

**patrik08** · 24th May 2008, 12:57

I dont say to swap design the file
http://ppk.ciz.ch/win_build/tree_cat_memo/Tree_Cat.zip
show only how to build a recursive function on model tree on XML
and other model to make the same on SQL or faster on sqlite3

if you have a recursive build model
you dont need this here ...

Qt Code:

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root->children[1]->append(new InternalItem());
    root->children[1]->children[0]->append(new InternalItem());
    root->children[1]->children[0]->children[0]->append(new InternalItem());

root->children[1]->append(new InternalItem());
    root->children[1]->children[0]->append(new InternalItem());
    root->children[1]->children[0]->children[0]->append(new InternalItem());

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sql tree query

#define MINISQL_TREE_NO_LIMIT "SELECT n.*, round((n.rgt-n.lft-1)/2,0) AS childs, count(*)+(n.lft>1) AS level, ((min(p.rgt)-n.rgt-(n.lft>1))/2) > 0 AS lower, (( (n.lft-max(p.lft)>1) )) AS upper FROM catememo n, catememo p WHERE n.lft BETWEEN p.lft AND p.rgt AND (p.root_id = n.root_id) AND (p.id != n.id OR n.lft = 1) GROUP BY n.root_id,n.id ORDER BY n.root_id,n.lft"

structure

query.exec("create table catememo (id INTEGER PRIMARY KEY AUTOINCREMENT,root_id INTEGER,name varchar(110),lft INTEGER,rgt INTEGER,oldid INTEGER,xmlattribute BLOB)");

Or online demo:
http://www.klempert.de/nested_sets/demo/

**init2null** · 25th May 2008, 05:55

I really don't think XML or databases would be useful, since I'm just trying to show the hierarchy of a QGraphicsScene for a fancy scene debugger I'm working on. The code you quoted was just there for debugging purposes, since it shows the bug. The model I wrote (not the test case in this post) can successfully show the hierarchy right now, except it crashes just like this example when it is expanded twice.

**jpn** · 25th May 2008, 09:19

The problem seems to be in TestModel::parent():

Qt Code:

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return createIndex(iindex->row(), 0, iindex->parent);
// vs.
return createIndex(iindex->parent->row(), 0, iindex->parent);

return createIndex(iindex->row(), 0, iindex->parent);
// vs.
return createIndex(iindex->parent->row(), 0, iindex->parent);

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**init2null** · 25th May 2008, 09:56

That's it. Thank you! If and when my QGraphicsScene visualization tool becomes useful, I'll be sure to post it here.

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