I created a QAbstractTableModel called PresetTableModel, and connected it to a QTableView. I implemented the rowCount, columnCount, and data functions. Everything works if I have rowCount return a fixed number, but as soon as I get it to return a variable value, the list view doesn't show any rows. The debug statement in the code below shows the size value starting at 0, but changing to 9 once the list gets populated.
int PresetTableModel::rowCount(const QModelIndex & /*parent*/) const
{
qDebug() << preset_list.count();
return preset_list.size();
}
Is there something else I need to do to force it to update the number of rows?
When modifying the underlying data, you must use the model's notification mechanism to notify the views. E.g, when appending data:
beginInsertRows(QModelIndex(), preset_list.size(), preset_list.size()+1); //notify that two rows will be appended (rows size() and size() + 1)
preset_list.append(something);
preset_list.append(somethingelse);
endInsertRows(); //notify views that you're done with modifying the underlying data
Accordingly, you have to call beginRemoveRows() and endRemoveRows() when removing rows, and emit dataChanged() when existing entries are updated.
On a side note, your rowCount() method should read
if (!parent.isValid())
return preset_list.size(); //top-level: return list size
else
return 0; //list item: no further children (flat list)
to limit the depth. Otherwise each item in the list has again preset_list.size() entries.
i use:
void refresh() {
emit dataChanged(index(0, 0),
index(rowCount(), columnCount())); // update whole view
emit layoutChanged();
}
Related
I have a SQL model that connects to a single table, this table will change the number of columns depending on certain conditions during the execution of the program. The model is connected to a QTableView.
I have a function that controls the number of columns at the end of the function i have a call to model->select(), to update the information of the model and tableView->reset(), to what i thought would rearrange the view adding or taking away columns.
The problem is that the view does not change from the original number of columns that it had. If i reduce the number i can see that the data change and show empty on the missing columns. Is there a command for the tableView to resize it self?
Editing the question
in the constructor of the class i'm reading the table and setting it to the view:
header = new QSqlTableModel(parent,data->m_db);
header->setTable("C"+QString::number(markTime.toSecsSinceEpoch())+"T");
header->select();
ui->heading->setModel(header);
ui->heading->show();
Every time that that the number of columns is changed is an SQL procedure to change the number of columns:
void ImportProcess::copyTable(QString oldTable, QString newTable)
{
QSqlQuery queryOld, queryNew;
queryOld.prepare("select * from :oldTable");
queryOld.bindValue(":oldTable",oldTable);
queryOld.exec();
if(queryOld.record().isEmpty()==true) return; //Old table was empty, nothing to copy
int oldColumn=queryOld.record().count();
QString replaceLine="insert into "+newTable+" values(";
while(queryOld.next()==true)
{
replaceLine.append(QString::number(queryOld.value(0).toInt()));
replaceLine.append(", "+queryOld.value(1).toString());
for(int y=0;y<(oldColumn < ui->columns->value() ? oldColumn : ui->columns->value());y++)
{
replaceLine.append(", "+QString::number(queryOld.value(y+2).toFloat()));
}
replaceLine.append(")");
queryNew.exec(replaceLine);
}
}
Then the header file is updated, and here is where I thought that the tableview will be redrawn:
void ImportProcess::updateHeadingTable()
{
QSqlQuery query;
query.exec("delete from C"+QString::number(markTime.toSecsSinceEpoch())+"T");
QString description= ui->Week->isChecked() == true ? "Week" : "Size";
query.exec("insert into C"+QString::number(markTime.toSecsSinceEpoch())+"T (id, description) values (101, '"+description+"')");
for(int x=0;x<ui->columns->value();x++)
{
query.exec("update C"+QString::number(markTime.toSecsSinceEpoch())+"T set col"+QString::number(x)+" = '30'");
}
header->select();
ui->heading->reset();
}
I believe you forgot about some protected methods:
void QAbstractItemModel::beginInsertColumns(const QModelIndex &parent, int first, int last);
void QAbstractItemModel::beginRemoveColumns(const QModelIndex &parent, int first, int last);
void QAbstractItemModel::endInsertColumns();
void QAbstractItemModel::endRemoveColumns();
Every time the number of column about to be change you should call first or second method. After change you should call third or fours method.
You can read about these methods in Qt documentation.
I am trying to get listview and tableview working together.
The listview must be used for display, the tableview must be used for editing data. The tableview is created on demand in a popup widget (and it may never be needed).
I populate the listview, on start, from a text file - each row a line, with 2 entries separated by a tab. Easy.
The tableview will have to edit 2 columns separately... also, on listview click, I must be able to retrieve the first part of the split...
I have created a model subclass of QStringListModel.
QListView *m_myView = new QListView();
StringList *m_myList = new StringList();
QTextStream in(&myFile);
while (!in.atEnd())
{
QString temp = in.readLine();
if(!temp.isEmpty())
m_myList->append(temp);
}
myFile.close();
m_myView->setModel(m_myList);
where
class StringList : public QStringListModel
{
public:
void append (const QString& string)
{
insertRows(rowCount(), 1);
QModelIndex m = index(rowCount() - 1);
setData(m, string, Qt::EditRole);
QStringList splist = string.split('\t');
setData(m, splist.at(0), Qt::ToolTipRole);
if(splist.size() > 1)
setData(m, splist.at(1), Qt::StatusTipRole);
else
setData(m, "", Qt::StatusTipRole);
qDebug() << data(m, Qt::EditRole).toString()
<< data(m, Qt::ToolTipRole).toString()
<< data(m, Qt::StatusTipRole).toString();
}
};
The EditRole displays correctly, the others display empty strings.
It seems that QStringListModel is incapable of storing anything except EditRole.
So I am left with 2 options - either do the split on each selection, and also when creating the table view, or - what I would like to try but don't know how - create a QStandardItemModel that can act as data sources for both the listview and the tableview, and can easily retrieve the partial data I require on click.
I thought I can simply use it to set the data on listview (like they do here).
QListView *m_myView = new QListView();
QStandardItemModel *m_myList = new QStandardItemModel();
QTextStream in(&myFile);
int r = 0;
while (!in.atEnd())
{
QString temp = in.readLine();
if(!temp.isEmpty())
{
QStringList splist = temp.split('\t'); // assume I know there will be 2 strings always
QStandardItem *item = new QStandardItem(splist.at(0));
m_myList->setItem(r, 0, item);
QStandardItem *item1 = new QStandardItem(splist.at(1));
m_myList->setItem(r, 1, item1);
++r;
}
}
myFile.close();
m_myView->setModel(m_myList);
connect(m_myListView, SIGNAL(clicked(QModelIndex)),
this, SLOT(listChangedSlot(QModelIndex)));
But this will only set the first string in the listview, I really need both, and I still don't know how to retrieve the data
void listChangedSlot(QModelIndex index)
{
qDebug() << m_myList->item(index.row(), 0)->data().toString()
<< m_myList->item(index.row(), 1)->data().toString();
} // shows empty strings
Or...
In the loading section, try:
if(!temp.isEmpty())
{
QStringList splist = temp.split('\t');
splist.append(QString()); // so I don't need to test
QStandardItem *item = new QStandardItem(temp);
m_myList->setItem(r, 0, item);
QModelIndex idx = m_myList->index(r, 0);
QMap<int, QVariant> roles;
roles.insert(Qt::UserRole + 1, QVariant(splist.at(0)));
roles.insert(Qt::UserRole + 2, QVariant(splist.at(1)));
roles.insert(Qt::DisplayRole, QVariant(temp));
m_myList->setItemData(idx, roles);
++r;
}
This works - displays fine and gets the correct content on click - but seems to be unusable for the tableview.
(And seems I am doing twice the work, with setItem and setItemData - so technically storing the content 3 times).
How can I get my listview have a datasource with 2 string items, show both, be able to set it on a tableview, and be able to retrieve the first item on click ?
I figured out a way to share the data source between the listview and tableview:
I create 3 columns - column 0 with the combined components, and columns 1 and 2 with the separated components.
The listview will display only column 0. For tableview, I will hide column 0.
The data I require for processing will be stored in columns 1 and 2. user edit of the data in tableview will require, upon accepting changes, the edit of corresponding column 0.
How should this be done by using the model->setData() method call?
I have derived a class called "MyStandardItemModel" from QStandardItemModel. I have made my third and fourth columns non-editable by overriding the protected virtual flags method. This is how it goes:
#define TX_PACKET_COLUMN (4u)
#define RX_PACKET_COLUMN (5u)
Qt::ItemFlags MyStandardItemModel::flags(const QModelIndex& index) const
{
if (index.column() == TX_PACKET_COLUMN || index.column() == RX_PACKET_COLUMN)
{
return (QStandardItemModel::flags(index) & ~Qt::ItemIsEditable);
}
else
{
return QStandardItemModel::flags(index);
}
}
...
//Set model
ui->testCaseTableView->setModel(model);
Having this done, I am not able to edit the cells in the third and fourth column.
Now, I want that when I double click on these cells, a pop-up dialog comes up. I will modify some data in the editable field of that dialog, and then copy it back to the non editable cells inside the code.
I tried to just write a doubleclick() handler for the QTreeView and just copy some data to the cells just to see if it is possible to copy data to the non-editable cells.
This operation is failing, and the data is not written into the non-editable cells.
Here you can find the double click handler:
void MainWindow::on_testCaseTableView_doubleClicked(const QModelIndex &index)
{
QVariant variant;
variant.toString() = "AA";
if((index.column() == TX_PACKET_COLUMN)||(index.column() == RX_PACKET_COLUMN))
{
model->setData(index, variant); // set new value
}
}
The setData(..) operation is clearing the already written data in the cells, but string "AA" is not getting written. Please suggest how to copy some data to non-editable cells inside the code.
QVariant set is empty. Nothing needs to be wrong in your model. Error is on this line:
variant.toString() = "AA";
change to:
QVariant variant("AA"); // just for testing anyway
As I indicated in my comment, you have to fix this first issue:
instead of:
QVariant variant;
variant.toString() = "AA";
you should write
QVariant variant = QLatin1String("AA");
In general, you would look into the setData(...) implementation for such cases whether you emit the data changed signal properly and so forth, but here you are entering a prior issue which can lead to problems, so let us fix that.
Note, you should use QLatin1String to avoid the unnecessary explicit conversion from raw char* to QString. This is a good practice in general, and this is available with Qt 4 as well as Qt 5.
Although, you could also use the QStringLiteral macro for creating a QString very efficiently with template magic out of your raw literal, but that requires C++11.
I implemented the removeRows() method according to the documentation. My data is stored in a QList. I can remove items just fine using:
bool MeasurementManager::removeRows(int row, int count, const QModelIndex &m) {
if(count > 1) {
qDebug() << "MeasurementManager: cannot remove more than one measurement";
return false;
}
beginRemoveRows(QModelIndex(), row, row+count-1);
list.removeAt(row);
endRemoveRows();
return true
}
However, when removing the last item I get the following error message, when executing beginRemoveRows():
ASSERT failure in QList<T>::at: "index out of range"
When removing the last item (leading to the crash) it obviously has to be in row 0, but as long as there are other items in the model I can remove the item in row 0 without any problems.
If I comment out the actual removal of my data like this
beginRemoveRows(QModelIndex(), row, row+count-1);
//list.removeAt(row);
endRemoveRows();
no crash occurs, so my assumption it, that something tries to access one of list's elements after the removal. However when stepping through the function the beginRemoveRows() method clearly is the culprit.
Any help where to start debugging would be appreciated!
I found the solution, my bad. I had connected to the ´selectionChanged()´ signal to a custom slot. This tried to access the recently deleted item in the table model.
I overlooked, that deselection a table item emits an selectionChanged() signal, too.
What you see is probably an artifact of code reordering introduced by optimizing the code.
Compile the code again with all optimizations disabled to avoid confusing the debugger.
Just had the same problem. Simply call reset() and remove the rows afterwards.
void QItemSelectionModel::reset() [virtual slot]
Clears the selection model. Does not emit any signals.
I was trying to remove all selected indices of a QTableView,
Now I use:
foreach (const QModelIndex & idx, model->selectionModel()->selectedIndexes())
{
model->removeRow (idx.row()); // Obviously bug
}
There's a obvious problem that once you remove the row, the row id is invalidated, w
As there's no function that takes directly the index (or does the index act like a iterator that will get invalidated when data changed?), I don't know what to do.
There is QPersistanceModelIndex class which keeps valid state of index. I tried and it seems to be working.
QList<QPersistentModelIndex> indexes;
foreach (const QModelIndex &i, ui->tableView->selectionModel()->selectedIndexes())
indexes << i;
foreach (const QPersistentModelIndex &i, indexes)
ui->tableView->model()->removeRow(i.row());
I hope it will help.