the listView does not show the currentIndex

the listView must show what you define in the delegate property

 ListView{
     id:l
    anchors.fill: parent
    model: ["data 1","data 2","data 3"]
    currentIndex : 2
    delegate: Text {
        Rectangle{
            color: index === l.currentIndex ? "green" : "red"
            height: 30
            width: 20
        }
        id: name
        text :"DATA : "  + modelData +  " index is : " + index + "; Listview currentindex is " +  l.currentIndex
        height: 100
        MouseArea{
            anchors.fill: parent
            onClicked: l.currentIndex  = index
        }
    }
 }