Set color to a QTableView row - qt

Question

void MyWindow::initializeModelBySQL(QSqlQueryModel *model,QTableView *table,QString sql){
model = new QSqlQueryModel(this);
model->setQuery(sql);
}
With this method i can set a QSQlQueryModels to my QTableviews.
But How i can set color to a row based on a cell value?

Answer 1

The view draws the background based on the Qt::BackgroundRole role of the cell which is the QBrush value returned by QAbstractItemModel::data(index, role) for that role.
You can subclass the QSqlQueryModel to redefine data() to return your calculated color, or if you have Qt > 4.8, you can use a QIdentityProxyModel:
class MyModel : public QIdentityProxyModel
{
QColor calculateColorForRow(int row) const {
...
}
QVariant data(const QModelIndex &index, int role)
{
if (role == Qt::BackgroundRole) {
int row = index.row();
QColor color = calculateColorForRow(row);
return QBrush(color);
}
return QIdentityProxyModel::data(index, role);
}
};
And use that model in the view, with the sql model set as source with QIdentityProxyModel::setSourceModel.
OR
You can keep the model unchanged and modify the background with a delegate set on the view with QAbstractItemView::setItemDelegate:
class BackgroundColorDelegate : public QStyledItemDelegate {
public:
BackgroundColorDelegate(QObject *parent = 0)
: QStyledItemDelegate(parent)
{
}
QColor calculateColorForRow(int row) const;
void initStyleOption(QStyleOptionViewItem *option,
const QModelIndex &index) const
{
QStyledItemDelegate::initStyleOption(option, index);
QStyleOptionViewItemV4 *optionV4 =
qstyleoption_cast<QStyleOptionViewItemV4*>(option);
optionV4->backgroundBrush = QBrush(calculateColorForRow(index.row()));
}
};
As the last method is not always obvious to translate from C++ code, here is the equivalent in python:
def initStyleOption(self, option, index):
super(BackgroundColorDelegate,self).initStyleOption(option, index)
option.backgroundBrush = calculateColorForRow(index.row())

Answer 2

Your best bet is to define a custom model (QAbstractTableModel subclass). You probably want to have a QSqlQueryModel as a member in this custom class.
If it's a read-only model, you need to implement at least these methods:
int rowCount(const QModelIndex &parent) const;
int columnCount(const QModelIndex &parent) const;
QVariant data(const QModelIndex &index, int role) const;
and for well behaved models also
QVariant headerData(int section, Qt::Orientation orientation, int role) const;
If you need the model to be able to edit/submit data, things get a bit more involved and you will also need to implement these methods:
Qt::ItemFlags flags(const QModelIndex &index) const;
bool setData(const QModelIndex &index, const QVariant &value, int role=Qt::EditRole);
bool insertRows(int position, int rows, const QModelIndex &index=QModelIndex());
bool removeRows(int position, int rows, const QModelIndex &index=QModelIndex());
What will actually change a row appearance lies in the return value of this method:
QVariant data(const QModelIndex &index, int role) const;
A dumb example:
QVariant MyCustomModel::data(const QModelIndex &index, int role) const
{
if ( !index.isValid() )
return QVariant();
int row = index.row();
int col = index.column();
switch ( role )
{
case Qt::BackgroundRole:
{
if(somecondition){
// background for this row,col is blue
return QVariant(QBrush (QColor(Qt::blue)));
}
// otherwise background is white
return QVariant(QBrush (QColor(Qt::white)));
}
case Qt::DisplayRole:
{
// return actual content for row,col here, ie. text, numbers
}
case Qt::TextAlignmentRole:
{
if (1==col)
return QVariant ( Qt::AlignVCenter | Qt::AlignLeft );
if (2==col)
return QVariant ( Qt::AlignVCenter | Qt::AlignTrailing );
return QVariant ( Qt::AlignVCenter | Qt::AlignHCenter );
}
}
}