I'm developing an application using QT5.0 and new to QT. Badly, i have not too much time for a long learning curve.
I have derived my own TableModel and set it to a editable TableView. TableView shows model's data, it works. But when i activate a cell on the tableview, the data disappears. I looked at the documentation and saw that QTableView is derived from QAbstractItemView class which have a signal called 'activated' and a slot called 'edit'. So, i think 'activated' signal is connected to 'edit' slot. But 'edit' is not virtual, so i can not override it. I may connect my child class to parents 'activated' signal but actually i do not know how to handle this signal in order to save the current data of the TableView object.
There is no problem if the code uses SqlTableModel. I think it handles the 'activated' signal but I'm not sure about these, just speculating..
What is the right way to do this?
Check your the data function:
QVariant TableModel::data(const QModelIndex &index, int role) const
if( !index.isValid() )
return QVariant();
if( role == Qt::DisplayRole || role == Qt::EditRole) {
return <your data>
}
return QVariant();
}
Ensure that you process the EditRole role.
Good luck!
Related
I'm new with Qt , so please bear with me .
I've successfully managed to populate a ListView from a StringList and a QList of Object*
What I'm struggling now with is to populate a ListView in QML using a class defined in C++ that derives QAbstractListModel.
Here's the prototype of my CPP class :
class MessageListEntryModel : public QAbstractListModel
{
Q_OBJECT
public:
enum eMLERoleTypes
{
MLERT_MSG = Qt::UserRole+1,
MLERT_COLOR
};
MessageListEntryModel(QObject* parent=0);
virtual ~MessageListEntryModel();
void AddEntry(QString aMessage, QColor aColor);
// pure virtuals implementations
QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const;
int rowCount(const QModelIndex &parent = QModelIndex()) const ;
int columnCount(const QModelIndex &parent = QModelIndex()) const ;
QModelIndex index(int row, int column, const QModelIndex &parent = QModelIndex()) const;
QModelIndex parent(const QModelIndex &child) const ;
QHash<int,QByteArray> roleNames();
private:
QList<MessageEntry*> m_vpMessages;
MessageEntry is a simple class that contains 2 memebers , a QColor and a QString (the class doesn't extend QObject).
I had to implement all the above functions since they're pure virtual in an underlying class (is this normal? so far in tutorials/samples people mentioned only about roleNames and data).
The implementation of roleNames and data are as following :
QHash<int,QByteArray> MessageListEntryModel::roleNames()
{
QHash<int,QByteArray> rez;
rez[MLERT_MSG]="message";
rez[MLERT_COLOR]="messagecolor";
return rez;
}
QVariant MessageListEntryModel::data(const QModelIndex &index, int role) const
{
qDebug()<<" Data asked for "<<index.row()<<" and role "<<role;
if (index.row()<0 || index.row()>=m_vpMessages.size())
{
return QVariant();
}
MessageEntry* entry = m_vpMessages[index.row()];
if (role == MLERT_MSG)
{
return QVariant::fromValue(entry->message);
} else if (role == MLERT_COLOR)
{
return QVariant::fromValue(entry->messageColor);
}
// should be unreachable code
return QVariant();
}
The QML portion of the List View is something like this :
ListView {
id: quickMessageListdata
model: quickListModel
delegate: Rectangle {
width: 400
height: 25
color:"#000000"
Text{
text: model.message
color: model.messagecolor
}
}
So far this is my understanding on how to implement things in CPP and QML.
For linking these two, I use the following code :
MessageListEntryModel* model =new MessageListEntryModel();
// Add various entries
...
// assign model in QML
m_pViewRef->rootContext()->setContextProperty("quickListModel",model);
With the code above, when running nothing is displayed in the ListView and I'm getting the following errors :
Unable to assign [undefined] to QString
Unable to assign [undefined] to QColor
I'm also registering the model class to be exported to QML (don't know if this is necessary) :
qmlRegisterType<MessageListEntryModel> ("dlti.exported",1,0,"MessageListEntryModel");
So it's quite obvious that either I missuderstood the proper use of a QAbstractListItem derived class OR I miss a simple vital key information.
I would appreciate some pointers to some relevant samples / tutorials (one that also shows you how to properly access data from the model in QML, since I've noticed that in CPP it never passes through the data function).
Also please notice that I'm using qt5 , so qt4.8 samples won't do the trick.
EDIT
After long hours of frustrations, I finally managed what was wrong with the damn thing :
My roleNames function signature was wrong !
The correct signature for overload is :
protected :
QHash<int,QByteArray> roleNames() const;
Please notice the protected and the const modifiers.
After declaring the function the correct way , it all worked fine.
For further notice, implementing data and rowCount was sufficient :).
Thanks for the help.
I will accept BaCaRoZzo's answer since I only manged to figure this out after looking over the code from the example.
As a side note, it works well with both message and model.message.
How do you implement the addition method? You should use a method like in the example provided in my comment.
From the docs:
An insertRows() implementation must call beginInsertRows() before
inserting new rows into the data structure, and it must call
endInsertRows() immediately afterwards.
You should have something like:
void MessageListEntryModel::add(params...)
{
beginInsertRows(QModelIndex(), rowCount(), rowCount()); // kindly provided by superclass
// object creation based on params...
m_vpMessages << objectCreated;
endInsertRows(); // kindly provided by superclass
}
with
int MessageListEntryModel::rowCount(const QModelIndex & parent) const {
Q_UNUSED(parent);
return m_vpMessages.count();
}
Also, #Jonathan Mee comment is correct: use just the role names inside the delegate as you defined them in the model. If everything else is correct that is the way to access data.
One of the best documentation piece to understand C++ models implementation and usage is the Model subclassing reference. In this document is clearly depicted which are the most important methods to subclass and for what purposes.
As for the methods to implement, it really depends on the needs. Depending on the possible actions on the model, different methods should be implemented (refer to the above link for full details). A model for a ListView in which items can be added/removed can inherit from QAbstractListModel and just rely on the default implementations for most of the functions. You just need data(), roleNames() and rowCount(), as you already saw in most examples.
If instead you also need to edit data not just adding/removing it, then you also need other functions, particularly setData(). It is also your duty to notify the attached view(s) with any modification of the model occurred in setData(), via the signal dataChanged(). Refer again to the above provide subclassing reference.
Note also that, if the add method is modified with the Q_INVOKABLE modifier, i.e. it is declared as
Q_INVOKABLE void add(params...);
in the model header, you can also call it from QML (since the model is set as a context property) and you can write, for instance:
ListView {
id: quickMessageListdata
model: quickListModel
delegate: Rectangle {
width: 400
height: 25
color:"#000000"
Text{
text: model.message
color: model.messagecolor
}
}
Component.onCompleted: {
quickListModel.add(params)
quickListModel.add(params)
}
}
to insert items in the view as soon as the view is created. Clearly the same approach can be applied to other QML signals so that you can react to QML events and trigger addition/removal behaviours.
Finally, you don't need to register the model with qmlRegisterType. For your current requirement it is superfluous.
Hmmm... I'm not super familiar with QML but I believe that this is your problem: http://qt-project.org/doc/qt-5/qtquick-modelviewsdata-cppmodels.html#qabstractitemmodel
According to the link it looks like you need to change your Text block to:
Text{
text: message
color: messagecolor
}
Further reading: http://qt-project.org/forums/viewthread/5491
I've also experienced hard times before when creating own list models with Qt C++. To avoid the development overhead for a C++ model, I started to use QSyncable (a existing QAbstractListModel implementation by Ben Lau). You can find it on GitHub here.
The best part of the project is the JsonListModel QML type. It can transform any variant JSON list that you create or fetch in QML to a full-featured QML ListModel. This saves a lot of time and effort for applications that e.g. work with JSON or REST services. You can find a detailed guide how it works here.
I want to display a tooltip for QTreeWidgetItem that's hovered. However, getting a tooltip is not a very fast process in my case, so I don't want to call setTooltip() for every single item. I want to do it on demand, on some event or signal. What's the easiest way to do it?
The best solution I've found is to subclass QTreeWidgetItem, override virtual QVariant data(int column, int role) const; and return a tooltip for this item when data is called for Qt::ToolTipRole.
I think that it should be easier to achieve what you want if you migrate to a QTreeView/Model pattern.
QAbstractItemModel has a role for tooltips: Qt::ToolTipRole
You could subclass a Model to reimplement the
QVariant QAbstractItemModel::data ( const QModelIndex & index, int role = Qt::DisplayRole ) const [pure virtual
method.
So, when receives a Qt::TooltipRole, it calculates/recovers from an internal cache.
I have the following (simplified) code to add QStandardItem's to a QStandardItemModel, attach the model to a QListView, and connect signals of my choice from the model to a function of my choice:
// MyUIContainer derives from QWidget
MyUIContainer::SetItems()
{
// Inside a member function where model/items are added to a QListView...
// This code does not show deletion of existing ItemSelectionModel
QStandardItemModel * model = new QStandardItemModel(ui->listView);
// In the real code, data is set in each QStandardItem
model->setItem( 0, new QStandardItem() );
model->setItem( 1, new QStandardItem() );
model->setItem( 2, new QStandardItem() );
connect(model,
SIGNAL(itemChanged(QStandardItem*)),
this,
SLOT(ReceiveChange(QStandardItem*)));
// I have also tried connecting to this signal - same problem described below
//connect(model, SIGNAL(dataChanged(const QModelIndex &, const QModelIndex &, const QVector<int>)), this, SLOT(ReceiveChange(const QModelIndex &, const QModelIndex &, const QVector<int>)));
ui->listView->setModel(model);
}
MyUIContainer::ReceiveChange(QStandardItem * item)
{
// Problem! This slot is called *three times*
// whenever the check state of an item changes
}
As the code comment indicates, there is a problem: The itemChanged() \ ReceiveChange() signal \ slot combination is called three times whenever the check state of a checkbox in the QListView changes once.
I understand that I can create my own Model class that is derived from QAbstractItemModel, and (if I understand correctly) handle mouse clicks in the view myself, emitting signals such as, for example, the itemChanged signal with a proper user-defined role so that a change in checkbox state can be handled only once.
However, the latter approach requires me to be careful to handle all possible scenarios of mouse clicks & keyboard events that could result in a changed checkbox state. I was hoping, and assuming, that this logic has been handled inside the Qt library itself, so that I don't have to - so that I can simply receive a signal (or some other message) when the check state of a checkbox changes.
Note that it seems that QListWidget (rather than QListView) also has exactly the same problem.
So, my question is: Without writing my own Model class derived from QAbstractItemModel - with its requirement that I myself write code to handle every possible way that a check state can change - how do I capture a changed check state (via a signal or otherwise) such that I can unambiguously capture every time a check state changes once and only once per check state change?
ADDENDUM
With apologies - as I took great care in ruling everything else out - Riateche's comment made it clear to me that the behavior is not supposed to work in the way this question highlighted. Finally, I have indeed tracked down the problem to the fact that I was calling connect() multiple times.
I have a QTableView that obtains the data from a custom model and it's edited using a custom delegate.
//...
view->setModel(stockModel);
view->setItemDelegateForColumn(0, nameDelegate);
When the user edits a specific cell it types some text (name for an object) and this text could be accepted by the program or not (the program doesn't want to have repeated names).
My solution for this was to the custom delegate to have a signal: notValidText(QModelIndex) and use the signal/slot mechanism to connect the signal to the tableview edit(QModelIndex) slot. This, from what i know, should reedit the cell in question:
//implementation of the delegate
void NameDelegate::setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index)
{
QLineEdit *line = static_cast<QLineEdit*>(editor);
if(!model->setData(index, line->text(), Qt::EditRole))
{
emit notValidData(index);
}
}
//connection of the view with the delegate
connect(nameDelegate, SIGNAL(notValidData(QModelIndex)), view, SLOT(edit(QModelIndex)));
Unfortunately this is not what happens, so i'm doing something wrong. If someone could give me a tip i would really appreciate.
I just put here some code to show what i did, ask if you need me to post anymore.
Thanks in advance
I have a QComboBox so the user can a network name from from a model column. I'm using code like this:
self.networkSelectionCombo = QtGui.QComboBox()
self.networkSelectionCombo.setModel(self.model.worldLinks)
self.networkSelectionCombo.setModelColumn(WLM.NET_NAME)
I'm using PySide, but this is realy a Qt question. Answers using C++ are fine.
I need to give the user the option of not selecting any network. What I'd like to do is add an extra item to the combo box called 'None'. However this will just get overridden by the model contents.
The only way I can think of is to create an intermediate custom view on this model column and use that to update the combo, then the view can handle adding in the extra 'magic' item. Does anyone know a more elegant way of doing this?
One possible solution is to subclass the model you are using in order to add there the extra item. The implementation is straight forward. If you call your model MyModel then the subclass would look like this (C++ used):
class MyModelWithNoneEntry : public MyModel
{
public:
int rowCount() {return MyModel::rowCount()+1;}
int columnCount() {return MyModel::columnCOunt();}
QVariant data(const QModelIndex & index, int role = Qt::DisplayRole) const
{
if (index.row() == 0)
{
// if we are at the desired column return the None item
if (index.column() == NET_NAME && role == Qt::DisplayRole)
return QVariant("None");
// otherwise a non valid QVariant
else
return QVariant();
}
// Return the parent's data
else
return MyModel::data(createIndex(index.row()-1,index.col()), role);
}
// parent and index should be defined as well but their implementation is straight
// forward
}
Now you can set this model to the combo box.