Listvyer

Listviews can help you display objects from a model in an attractive way. To use a list view, you have to keep track of three things:

1. En modell, som innehåller data som du vill att din listvy ska visa
2. En delegat, som definierar hur varje element i modellen kommer att visas
3. Själva listvyn, som visar information från modellen enligt delegaten

Om du vill ha ytterligare klargöranden, har Qt-dokumentationen en informativ sida om ämnet.

Skapa en grundläggande listvy

En listvy har två grundläggande egenskaper som vi måste ta hänsyn till:

• model, which accepts the data or the id of the object that holds the data
• delegate, which accepts the component we will use to display the data in the model

import QtQuick 2.15
import QtQuick.Controls 2.15 as Controls
import QtQuick.Layouts 1.15
import org.kde.kirigami 2.20 as Kirigami

Kirigami.Page {

    ListView {
        id: myList

        // Att tillhandahålla ett tal för modellegenskapen genererar så många dataposter med början
        // på 0.
        model: 200

        delegate: Kirigami.BasicListItem {
            label: "Item " + modelData
        }
    }
}

In cases where your model data only contain a single piece of data, like in the example above, you can just grab the data in the model by referencing modelData.

En anmärkning om delegater: Om din modell innehåller objekt med data i namngivna egenskaper, exponeras namnet på egenskaperna automatiskt till din delegat och du behöver bara använda namnen i din delegat.

ListModel {
    id: myModel
    ListElement { type: "Item"; number: 0 }
    ListElement { type: "Item"; number: 1 }
    ListElement { type: "Item"; number: 2 }
    ListElement { type: "Item"; number: 3 }
}

ListView {
    id: myList

    model: myModel

    delegate: Kirigami.BasicListItem {
        label: type + " " + number
    }
}

Kirigami offers a number of components that have been designed specifically for use in list views, such as Kirigami.BasicListItem , Kirigami.CheckableListItem and Kirigami.SwipeListItem , all of which build upon Kirigami.AbstractListItem . There are also Kirigami.CheckDelegate , Kirigami.RadioDelegate , and Kirigami.SwitchDelegate , which are designed to take advantage of those specific controls.

However, you are not limited to using these components and you can choose whichever ones you wish. This may require some tweaking of your layout.

Platsmarkeringsmeddelanden

In some cases, you might want to use a list view that is empty until the user does something. In these situations, using a Kirigami.PlaceholderMessage can be an attractive way of telling your user that the list is empty and that they can do something about it.

You will generally want to place a placeholder message in the center of the ListView and you will likely not want it to span the entire width of the ListView. You will obviously also want it to be hidden once the ListView's model becomes populated with data. Thankfully, ListViews have a property named count that makes doing this quite easy.

You might also want to add a helpful action to your placeholder message. This can be done by attaching an action to the PlaceholderMessage.helpfulAction property.

ListView {
    id: myList

    model: ListModel { id: myModel }

    delegate: Kirigami.BasicListItem {
        label: text
    }

    Kirigami.PlaceholderMessage {
        anchors.centerIn: parent
        width: parent.width - Kirigami.Units.largeSpacing * 4
        visible: myList.count === 0
        text: "Add something to me!"

        helpfulAction: Kirigami.Action {
            icon.name: "list-add"
            text: "Add"
            onTriggered: myModel.append({"text": "Hello!!"})
        }
    }
}