It sounds trivial, but I could not find the function to show the last added element in a QListView.
It works with a model
// Create model
model = new QStringListModel(this);
// Make data
QStringList List;
// Populate our model
model->setStringList(List);
// Glue model and view together
listView->setModel(model);
Elements are added with
void WidgetMessageList::addString(const QString & message)
{
if(model->insertRow(model->rowCount())) {
QModelIndex index = model->index(model->rowCount() - 1, 0);
model->setData(index, message);
}
}
In this function the shown element should also be the last.
QAbstractItemView::scrollTo
Scrolls the view if necessary to ensure that the item at index is
visible. The view will try to position the item according to the given
hint.
http://doc.qt.io/archives/qt-4.8/qabstractitemview.html#scrollTo
Create a class attibute to hold the last index
Connect QAbstractItemModel::rowsInserted to a slot in your application
In the slot update the index accordingly
Related
I have created a custom list model following this guide Creating a cusotm model for a QListView. I am able to show a list of custom objects (such as the Employee as in the example) but I don't know how to retrieve back the selected ones (can I retrieve back the "linked" objects directly?).
Maybe do I have to do something with this command:
myLV->selectionModel()->selectedIndexes();
But I don't really know how to retrieve back the original custom objects.
[EDIT]
So far I have solved retrieving back the object adding a custom method inside my custom list model:
Employee* MyEmployeeListModel::getAtSelectedIndex(const QModelIndex& index){
return employees_.at(index.row());
}
And then calling this on the main window:
QModelIndexList selectedRows;
QItemSelectionModel * selmodel = ui->employeesLV->selectionModel();
selectedRows = selmodel->selectedRows();
MyEmployeeListModel* currModel = dynamic_cast <MyEmployeeListModel*>(ui->employeesLV->model());
for (const QModelIndex & index : selectedRows){
Employee* item=currModel->getAtSelectedIndex(index);
if (item) {
// do something with the item
}
}
Now what I am willing to know is if this is the real best practice or not.
I'm using the following code with a QTreeView (ui->treeMessages), but this should work with a QListView as well:
QModelIndexList selectedRows;
QItemSelectionModel * selmodel = ui->treeMessages->selectionModel();
selectedRows = selmodel->selectedRows();
for (const QModelIndex & index : selectedRows)
{
const QModelIndex sourceIndex = m_sortFilterModel->mapToSource(index);
ItemData * item = sourceIndex.internalPointer();
if (item) {
// do something
}
}
I'm making a Qt5.7 application where I am populating a QListView after reading stuff from a file. Here's the exact code of it.
QStringListModel *model;
model = new QStringListModel(this);
model->setStringList(stringList); //stringList has a list of strings
ui->listView->setModel(model);
ui->listView->setEditTriggers(QAbstractItemView::NoEditTriggers); //To disable editing
Now this displays the list just fine in a QListView that I have set up. What I need to do now is to get the string that has been double clicked and use that value elsewhere. How do I achieve that?
What I tried doing was to attach a listener to the QListView this way
... // the rest of the code
connect(ui->listView, SIGNAL(doubleClicked(QModelIndex)), this, SLOT(fetch()));
...
And then I have the function fetch
void Window::fetch () {
qDebug() << "Something was clicked!";
QObject *s = sender();
qDebug() << s->objectName();
}
However the objectName() function returns "listView" and not the listView item or the index.
The signal already provides you with a QModelIndex which was clicked.
So you should change your slot to this:
void Window::fetch (QModelIndex index)
{
....
QModelIndex has now a column and a row property. Because a list has no columns you are interessted in the row. This is the index of the item clicked.
//get model and cast to QStringListModel
QStringListModel* listModel= qobject_cast<QStringListModel*>(ui->listView->model());
//get value at row()
QString value = listModel->stringList().at(index.row());
You should add the index as parameter of your slot. You can use that index to access the list
Your code should be some thing like this.
void Window::fetch (QModelIndex index) {
/* Do some thing you want to do*/
}
I'm working on an application using the Qt library (version 4.8).
I have a QTreeView with a QStandardItemModel. My widget looks like that:
Item1
subitem11
subitem12
Item2
subitem21
subitem22
Item3
subitem31
subitem32
Here is how I add the items to my QTreeView:
model->setItem(0, 0, item1);
item1->setChild(0, 0, subitem12);
I want to take an action only when the user double cliked an item (and do nothing when he clicked a subitem). So I use the doubleClicked(const QModelIndex & index) signal.
I want to process the information about the item/subitem which was double cliked by the user. So I get the row of my item/subitem:
index.row();
But every time I try to reference to the item/subitem to display its name or check if it has children, I can only access the items:
index.model()->item(row)->text();
My question is: how can I acces the subitems (vbetween items abd subitems) in my slot? Or how can I prevent them from emitting the signal? I can't disable them - it would be too confusing for the user.
Edit: The problem is that every time I click on an item or subitem and execute:
index.model()->item(row)->hasChildren();
or:
index.model()->item(row)->parent() == 0;
I get true as result. So I can reference only the items.
My question is: What is the correct way to reference to subitems?
When you are trying to access model items by row index, the model returns top-level item at that row. Use itemFromIndex instead:
auto item = index.model()->itemFromIndex(index);
if (item && item->hasChildren()){
// item is not a leaf
}
EDIT index.model() returns QAbstractItemModel*, so a cast is also necessary here (or, better, storing a pointer to the standard model somehwere in the code).
I would do it like this:
// Define your custom role to store item type.
enum MyRoles
{
ItemTypeRole = Qt::UserRole + 1
};
// Define item types.
enum ItemType
{
Primary,
Secondary
};
Than set the proper item type for all your items:
QStandardItem* item = new QStandardItem("Item1");
item->setData(Primary, ItemTypeRole);
QStandardItem* subItem = new QStandardItem("SubItem1");
subItem->setData(Secondary, ItemTypeRole);
And in your slot connected to the doubleClicked signal acces the type like this:
ItemType type = static_cast<ItemType>(index.data(ItemTypeRole).toInt());
if (type == Primary)
std::cout << "It's a Primary item!" << std::endl;
else if (type == Secondary)
std::cout << "It's a Secondary item!" << std::endl;
You can't disable the signal for the subitems. However, you can check if an item has a parent. It it doesn't, it is an item and if it does, it's a subitem.
if (item->parent() != 0)
.. //subitem
else
.. //item
An alternative would be to use the data() function to set some special value to distinguish between the two.
item1->setData(QVariant("item"));
subitem1->setData(QVariant("subitem"));
Then query the value in your doubleclick handler:
QVariant var = item->data();
if (var.toString() == "item")
...
else if (var.toString() == "subitem")
...
I have a list view with a custom model. The model allows me to add text to the bottom of the list (using 'addText(const QString&)') and to remove items from the top of the list (using 'removeItemsFromTop(int _iCount)').
What is the best way to add text to the view and keep the model size under some maximum (lets say 'MAX_LIST_SIZE'), while always maintaining the view (i.e. current selection and items in view should not change when items are removed).
The solution should preferably be a function that I can use wherever I'm using my custom model.
I have looked at indexAt(...), scrollTo(...), currentIndex(...) and setCurrentIndex(...) methods on QListView, but I can't figure out how to put all of this together.
So far I have (for auto scrolling the view)
// add items here ...
// cleanup
QModelIndex indexViewTop = listView->indexAt(QPoint(8, 8));
if (listModel->rowCount() > MAX_SIZE)
{
int iRemoveCount = (listModel->rowCount() - MAX_SIZE) + MAX_SIZE/10;
listModel->clearTextFromFront(iRemoveCount);
listView->scrollTo(indexViewTop.sibling(indexViewTop.row() - iRemoveCount, 0), QAbstractItemView::PositionAtTop);
}
This is supposed to scroll the list view as items are removed to keep the view consistent, but indexAt(...) always returns an invalid index.
For keeping the selection consistent I tried:
// add items her ...
// cleanup
if (listModel->rowCount() > MAX_SIZE)
{
int iCurrentViewIndex = listView->currentIndex().row();
int iRemoveCount = (listModel->rowCount() - MAX_SIZE) + MAX_SIZE/10;
listModel->clearTextFromFront(iRemoveCount);
listView->setCurrentIndex(listModel->index(iCurrentViewIndex - iRemoveCount, 0));
}
This seems to work, but I'm still stuck on the auto scrolling.
I did a queue-like table model implementation. I think it is similar for QAbstractItemModel. Best way would be to use QQueue to store data.
Now, this is a snipped for QAbstractTableModel (which is subclass of QAbstractItemModel so it should work; mEvents is QQueue):
// custom table for inserting events
void EventPreviewTableModel::insertEvent(const DeviceEvent &event) {
beginInsertRows(QModelIndex(), 0, 0);
mEvents.enqueue(event);
endInsertRows();
if (mEvents.size() > SIZE) {
beginRemoveRows(QModelIndex(), mEvents.size(), mEvents.size());
mEvents.dequeue();
endRemoveRows();
}
}
And also override data() and rowCount() to serve correct data.
For second part using ItemIsSelected flag for items you want to have selected is done through: Qt::ItemFlags QAbstractItemModel::flags(const QModelIndex & index)
This is my current approach and it seems to work well:
void addTitlesToList(Model *model, QListView *view, std::vector<Object*> &items)
{
QScrollBar *pVerticalScrollBar = view->verticalScrollBar();
bool bScrolledToBottom = pVerticalScrollBar->value() == pVerticalScrollBar->maximum();
QModelIndex indexViewTop = view->indexAt(QPoint(8, 8));
// add to model
model->pushItems(items);
// cleanup if model gets too big
if (model->rowCount() > model->maxListSize())
{
int iCurrentViewIndex = view->currentIndex().row();
int iRemoveCount = (int)(model->rowCount() - model->maxListSize()) + (int)model->maxListSize()/10;
model->removeItemsFromFront(iRemoveCount);
// scrolls to maintain view on items
if (bScrolledToBottom == false)
{
_pView->scrollTo(indexViewTop.sibling(indexViewTop.row() - iRemoveCount, 0), QAbstractItemView::PositionAtTop);
}
// maintain selection
if (iCurrentViewIndex >= iRemoveCount)
{
view->setCurrentIndex(_pModel->index(iCurrentViewIndex - iRemoveCount, 0));
}
else
{
view->setCurrentIndex(QModelIndex());
}
}
// move scroll bar to keep new items in view (if scrolled to the bottom)
if (bScrolledToBottom == true)
{
view->scrollToBottom();
}
}
One issue I had with indexAt(QPoint(...)) is that I was calling it after adding the items to the list, which seems to cause it to always return an invalid index. Calling indexAt before anything is added to the model seems to work.
I also added automatic 'scroll to bottom' if already there (i.e. the view either stays fixed on specific items or sticks to the latest items if scrolled all the way to the bottom).
I wave a QListView that is backed by a QStandardItemModel. Under certain circonstances, the QStandardItem are made checkable. A checkbox gets displayed besides the item's display. At some point, I want to remove hide the QStandardItem checkbox. I set its checkable state to false but it doesn't hide the checkbox (though it cannot be checked anymore).
The only way I have found of hiding the checkbox is to replace the item with a new one. This doesn't seem the proper way to preceed.
This is the code:
MyModel::MyModel(QObject *parent):QStandardItemModel(parent){}
void MyModel::createItem(int row, const QString &text)
{
setItem(row, new QStandardItem(text));
}
void MyModel::setCheckable(int row)
{
item(row)->setCheckState(Qt::Unchecked);
item(row)->setCheckable(true); // A checkbox appears besides the text
}
void MyModel::hideCheckBox(int row)
{
item(row)->setCheckState(Qt::Unchecked);
item(row)->setCheckable(false); // does not work
// I need to completely replace the item for the checkbox to disapear.
// This doesn't seem the proper way to proceed
setItem(row, new QStandardItem(item(row)->data(Qt::DisplayRole).toString()));
}
Is there better way to proceed?
When you call setCheckState or setCheckable, the qt will update the data of list item by adding or setting a Qt::CheckStateRole data. If the Qt::CheckStateRole data is existed, the check icon will be shown. So you need remove it from the data map of the list item.
Finally, the code of hideCheckBox should be:
void MyModel::hideCheckBox(int row)
{
// check the item pointer
QStandardItem* pitem = item(row);
if (pitem == NULL) return;
// find and delete the Qt::CheckStateRole data
QMap<int, QVariant> mdata = itemData(pitem->index());
if (mdata.remove(Qt::CheckStateRole))
{
setItemData(pitem->index(), mdata);
}
}
Hope it useful. :)
I think the presence of the check boxes in items defined by item flags, so that I would write the function in the following way:
void MyModel::hideCheckBox(int row)
{
// Does not set the Qt::ItemIsUserCheckable flag.
item(row)->setFlags(Qt::ItemIsSelectable | Qt::ItemIsEnabled);
}