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.
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.
My QTableView doesn't show strings from a QStringList.
In QTableWidget I have QTableWidgetItems. Must I set the strings manually or will the view show them automatically? In all the tutorials I don't see a "->setItem", they appear automatically.
I have 2 QLineEdits that give the QStrings to my Model :
void View::pushButtonClicked() {
meinModel->setData(txtname->text(), txtvalue->text());
}
In setData I push the Strings in two QLists.
names.push_back(name);
values.push_back(value);
I emit a dataChanged signal with the index from topleft and bottomright.
QModelIndex topLeft = createIndex(names.size()+1,0);
QModelIndex bottomRights = createIndex(names.size()-1,1);
emit dataChanged(topLeft, bottomRights);
I have a QAbstractTableModel and so i override the columnCount, rowCount and data Method.
In my data() Method I return my value and name:
QString returnValue;
if(0 == index.column()) { returnValue = names.at(index.row()); }
All of this compiles without warnings, but doesn't work correctly :( Is there something I'm doing obviously wrong?
One obvious problem is that you didn't get the semantics of dataChanged correctly. dataChanged means that an existing item has changed its value. When you change the structure of the model by adding/removing rows or columns, you have to enclose the modification in beginXxx and endXxx calls - see this answer for details.
For example:
void MyModel::setData(const QString & name, const QString & value) {
beginInsertRows(QModelIndex(), names.size(), names.size());
names.push_back(name);
values.push_back(value);
endInsertRows();
}
I want to use a QTableView to show different roles of an item, e.g. column 1 shows the DisplayRole data, column 2 shows UserRole, column 3 shows UserRole+1, etc
I've created this by making my own item delegate and assigning it to the appropriate column. However, to get access to the same item the delegates have to access their siblings. For example, here's my setEditorData function:
void UserRoleDelegate::setEditorData(QWidget *editor, const QModelIndex &index) const
{
QModelIndex baseIndex = index.sibling(index.row(),0);
QVariant v = baseIndex.data(Qt::UserRole);
if(v.isValid())
static_cast<QLineEdit*>(editor)->setText(v.toString());
}
Right now, it's hardcoded that column 0 contains the real object and other columns just access that via the sibling function. I'm worried, though, that it's fragile in that changing the column order will break it.
There are obvious ways to manage that, but I'm just wondering if I'm taking the right approach. Is there a better option to display different aspects of the same item?
To avoid possible code rewrite you simple could use the enumeration for your column numbers. For example:
enum ColumnNumber {
Base,
Sub1,
Sub2
}
And in your delegate's code:
[..]
QModelIndex baseIndex = index.sibling(index.row(), Base);
Thus, if you need to change the column order, you simply need to change the order of your enum values. The rest of code will work correctly as it is.
WRT to item delgate usage - it looks rather strange. Such things used to made in the model class, especially in QAbstractItemModel::data(...) function, using it with Qt::EditRole role. For example:
QVariant Model::data(const QModelIndex &index, int role) const
{
if (role == Qt::EditRole) {
// Get the data that stored in the first column
// ..
return data;
}
[..]
}
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!
I have a QDirModel whose current directory is set. Then I have a QListView which is supposed to show the files in that directory. This works fine.
Now I want to limit the files shown, so it only shows png files (the filename ends with .png). The problem is that using a QSortFilterProxyModel and setting the filter regexp will try to match every parent of the files as well. According to the documentation:
For hierarchical models, the filter is
applied recursively to all children.
If a parent item doesn't match the
filter, none of its children will be
shown.
So, how do I get the QSortFilterProxyModel to only filter the files in the directory, and not the directories it resides in?
As of Qt 5.10, QSortFilterProxyModel has the option to filter recursively. In other words, if a child matches the filter, its parents will be visible as well.
Check out QSortFilterProxyModel::recursiveFilteringEnabled.
For people like me who are interested in the following behaviour : if a child matches the filter, then its ancestors should not be hidden :
bool MySortFilterProxyModel::filterAcceptsRow(int source_row, const QModelIndex & source_parent) const
{
// custom behaviour :
if(filterRegExp().isEmpty()==false)
{
// get source-model index for current row
QModelIndex source_index = sourceModel()->index(source_row, this->filterKeyColumn(), source_parent) ;
if(source_index.isValid())
{
// if any of children matches the filter, then current index matches the filter as well
int i, nb = sourceModel()->rowCount(source_index) ;
for(i=0; i<nb; ++i)
{
if(filterAcceptsRow(i, source_index))
{
return true ;
}
}
// check current index itself :
QString key = sourceModel()->data(source_index, filterRole()).toString();
return key.contains(filterRegExp()) ;
}
}
// parent call for initial behaviour
return QSortFilterProxyModel::filterAcceptsRow(source_row, source_parent) ;
}
We ran into something similar where I work, and ended up making our own proxy model to do our filtering. However, looking through the documentation for what you want (which seems like it would be a more common case), I came across two possibilities.
You might be able to set a name filter on the QDirModel and filter things that way. I have no idea if this will work like you want, or if the name filters apply to directories also. The documentation is kind of sparse on these.
Subclass the QSortFilterProxyModel and override the filterAcceptsRow function. From the documentation:
Custom filtering behavior can be achieved by reimplementing the filterAcceptsRow() and filterAcceptsColumn() functions.
Then you could presumably use the model index to check if the index item is a directory (automatically accept) or a file (filter on filename).
derive qsortfilterproxymodel and then...
bool YourQSortFilterProxyModel::filterAcceptsRow ( int source_row, const QModelIndex & source_parent ) const
{
if (source_parent == qobject_cast<QStandardItemModel*>(sourceModel())->invisibleRootItem()->index())
{
// always accept children of rootitem, since we want to filter their children
return true;
}
return QSortFilterProxyModel::filterAcceptsRow(source_row, source_parent);
}