Listview/delegates coloring

Sydes

Hi, I just started with Qt programming and have a question about coloring in Listviews/delegates.

How can I make a list with different background colors depending on the values of the list items.
I would like to have an alternating color (black and darkgrey) for items that have the same value in a certain field.

ex. I would like to have coloring determined by the "value" field.

name: "test_10", value: 1 -> black
name: "test_02", value: 1 -> black
name: "test_30", value: 1 -> black
name: "test_14", value: 2 -> darkgrey
name: "test_25", value: 2 -> darkgrey
name: "test_16", value: 4 -> black
name: "test_27", value: 7 -> darkgrey
name: "test_18", value: 7 -> darkgrey
name: "test_09", value: 7 -> darkgrey
name: "test_11", value: 9 -> black

The list is sorted by value. But the numbers in value are not sequential.
I found something on how to highlight according to color, but i only works with predefined values.

Item {
id: contactDelegate
height: 21
anchors.left: parent.left
anchors.right: parent.right

Rectangle {
color: model.value == 2 ? colors.darkgrey: colors.black
....

I thought of looking to the "Value" field of the previous item in the list, but I don't know how to.

My second question is in the same line. In an alphabetically sorted list I would like to do the same, thus change color each time the first letter of a certain value changes, but not all letters are present (ex. a.., c... d... e... k... l... y... z...) . How can this be accomplished?

Could any of you help me out?

Thx

RajeeshRaveendran

HI,

Yes you can keep the prev value and while drawing current delegate validate that. I think below pseudo will work for u(I did not tried):

ListView {
property bool toggle: false
property int currValue: 0
property color rowColor: toggle ? "black" : "darkGray"

function getValue(value) {
	if(currValue != value) {
		toggle = !toggle;
		currValue = value;
	}
	return value;
}

delegate: Rectangle {
Text {
text: getValue(model.value)
}
color: rowColor
}
}

vladstelmahovsky

@Sydes lets model return color for the delegate

VRonin

just set the Qt::BackgroundRole for the same index to the colour you want and it will work out of the box. no need to custom use delegates or views

Wurgl

@VRonin Yes for QStandardItemModel, No for QListStringModel … not all Q*Models support all roles.

VRonin

Any reason why you can't use QStandardItemModel? in that case subclass QStyledItemDelegate and reimplement paint

void QStyledItemDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
    Q_ASSERT(index.isValid());

    QStyleOptionViewItem opt = option;
    initStyleOption(&opt, index);
/////////////////////////////////////
// Set the background based on the content
if(index.data().toInt()==1)
opt.backgroundBrush = QBrush(Qt::red);
/////////////////////////////////////
    const QWidget *widget = option.widget;
    QStyle *style = widget ? widget->style() : QApplication::style();
    style->drawControl(QStyle::CE_ItemViewItem, &opt, painter, widget);
}