Layouts, ListViews y Cards

Organización del contenido

Ahora que entendemos cómo funcionan las páginas, es hora de añadir cosas a la nuestra. Revisaremos una serie de componentes y elementos de diseño importantes que serán de utilidad para diseñar nuestra aplicación.

¡No se asuste por los grandes trozos de código! Repasaremos todo lo que no hayamos cubierto antes y, al final de esta sección, tendrá una aplicación de aspecto impecable.

ListViews

If you've ever used Discover, NeoChat, or Plasma's System Settings, you will have come across a ListView. Quite simply, it lets you display data on a list.

Kirigami.CardsListView {
    id: cardsView
    model: kountdownModel
    delegate: kountdownDelegate
}

Eso parece críptico, pero no se preocupe. Empecemos por el principio.

We add this component inside our Kirigami.ScrollablePage from the last tutorial.

We're using Kirigami.CardsListView , which is a ListView that allows us to easily display cards in a list. However, ListViews are made to show data taken from a model - to automatically populate itself from a set of data that we point it to. That's where the model property comes in: in this example, it's pointing to kountdownModel.

Modelo

ListModel {
    id: kountdownModel
    // Cada ListElement es un elemento de la lista que contiene información
    ListElement {
        name: "Dog birthday!!"
        description: "Big doggo birthday blowout."
        date: 100
    }
}

We add our kountdownModel inside our Kirigami.ApplicationWindow from the last tutorial.

A model defines the way that a data entry is structured. Our kountdownModel will consist of only one element for now. By looking at our ListElement above, we can see how the data of our kountdownModel are structured: it contains a name, a description, and a date. This isn't set in stone, and you may have different sorts of data in your model. The first two are just strings, and the third is a number we're using as a placeholder.

Los modelos también son útiles porque se pueden modificar mediante el uso de varios métodos. Algunos importantes son:

• ListModel.append(yourobject: jsobject) adds a JavaScript Object yourobject to the ListModel, and places it after the last item in the model. For this to happen correctly, you must provide a JavaScript Object with the correct properties and corresponding datatypes.
• ListModel.get(index: int) returns the JSObject at the index location you provide.
• ListModel.remove(index: int, count: int) removes the JSObject at the provided index location, and as many after that index location as you put in count (1 includes only the JSObject at the provided index)
• ListModel.set(index: int, yourobject: jsobject) changes the item at the provided index location with the values provided in yourobject. Same rules as with append().

Delegado

While our kountdownModel contains the data that will be displayed, our kountdownDelegate will handle how the data will be displayed in the ListView. Kirigami.CardsListView was designed to display card-type delegates, and we have indeed used a Kirigami.AbstractCard element as our delegate in the excerpt above.

Los delegados reciben automáticamente las propiedades de los ListElements que hemos especificado en nuestro modelo. Por lo tanto, podemos referirnos simplemente a las propiedades name, description y date de nuestros ListElements como si fueran una variable convencional dentro de nuestro delegado.

Construyendo nuestra tarjeta de delegado

The Component that will represent our delegate can be added inside our Kirigami.ApplicationWindow . We will then proceed by checking what each part of our delegate component does.

Component {
    id: kountdownDelegate
    Kirigami.AbstractCard {
        contentItem: Item {
            // implicitWidth/Height definen la anchura/altura natural de un elemento si no se indica
            // otra anchura o altura. La siguiente preferencia define el tamaño preferido de un
            // componente en función de su contenido
            implicitWidth: delegateLayout.implicitWidth
            implicitHeight: delegateLayout.implicitHeight
            GridLayout {
                id: delegateLayout
                anchors {
                    left: parent.left
                    top: parent.top
                    right: parent.right
                }
                rowSpacing: Kirigami.Units.largeSpacing
                columnSpacing: Kirigami.Units.largeSpacing
                columns: root.wideScreen ? 4 : 2

                Kirigami.Heading {
                    Layout.fillHeight: true
                    level: 1
                    text: (date < 100000) ? date : i18n("%1 days", Math.round((date-Date.now())/86400000))
                }

                ColumnLayout {
                    Kirigami.Heading {
                        Layout.fillWidth: true
                        level: 2
                        text: name
                    }
                    Kirigami.Separator {
                        Layout.fillWidth: true
                        visible: description.length > 0
                    }
                    Controls.Label {
                        Layout.fillWidth: true
                        wrapMode: Text.WordWrap
                        text: description
                        visible: description.length > 0
                    }
                }
                Controls.Button {
                    Layout.alignment: Qt.AlignRight
                    Layout.columnSpan: 2
                    text: i18n("Edit")
                    // onClicked: pendiente de hacer... ¡pronto!
                }
            }
        }
    }
}

implicitWidth e implicitHeight

The first part we will take a look at is how to manage the width and height of our component:

Kirigami.AbstractCard {
    contentItem: Item {
        implicitWidth: delegateLayout.implicitWidth
        implicitHeight: delegateLayout.implicitHeight
        GridLayout {
            id: delegateLayout
            ...
        }
    }
}

Looking at our Kirigami.AbstractCard , the first properties we set are implicitWidth and implicitHeight. We have set these to the delegateLayout.implicitWidth and delegateLayout.implicitHeight, i.e. the implicitWidth and implicitHeight of the GridLayout element. Implicit widths and heights are properties that are set as a default, i.e. if there is no explicit width or height set for these components. We have therefore set the implicitWidth and implicitHeight of our Kirigami.AbstractCard to that of the GridLayout below to ensure it does not spill out of the card.

Diseños

The GridLayout is inside the Item component we have provided for the property contentItem. This is the Item that contains what will be displayed in your card.

También necesitamos escoger un diseño para nuestros componentes, de modo que no se apilen unos encima de otros. Existen tres tipos principales entre los que podemos escoger:

• ColumnLayout organiza los componentes verticalmente, en una única columna
• RowLayout organiza los componentes horizontalmente, en una única fila
• GridLayout organiza los componentes en una cuadrícula con una composición de su elección

Con ColumnLayout y RowLayout, todo lo que tenemos que hacer es escribir nuestros componentes dentro del componente Layout. Como puede ver, hemos optado por un GridLayout, lo que implica un poco más de trabajo manual.

GridLayout {
    id: delegateLayout
    anchors {
        left: parent.left
        top: parent.top
        right: parent.right
    }
    rowSpacing: Kirigami.Units.largeSpacing
    columnSpacing: Kirigami.Units.largeSpacing
    columns: root.wideScreen ? 4 : 2
    ...
}

The first thing you see is our anchors. QtQuick's anchoring system provides a useful way of making sure your components are positioned in certain parts of a parent component. We have anchored our GridLayout to the left, top, and right of the parent card, ensuring our content stretches across the whole card.

A continuación, especificamos el espacio entre las filas y columnas dentro de nuestra cuadrícula para que nuestros componentes no se amontonen. Kirigami proporciona una serie de útiles unidades predefinidas para usar con este propósito:

As you might remember, root is the id of our Kirigami.ApplicationWindow . It provides the wideScreen property, used to determine whether the current device screen is a widescreen (i.e. a computer monitor or a phone in landscape). We use a ternary conditional here to vary the number of columns in our grid depending on the screen we are using: if it's a widescreen, the grid will have 4 columns, else it will have 2.

Componentes interiores

Podríamos crear tres etiquetas dentro de nuestro componente delegado y darlo por terminado. Pero eso no se vería particularmente bien.

GridLayout {
    ...
    Kirigami.Heading {
        Layout.fillHeight: true
        level: 1
        text: date
    }

    ColumnLayout {
        Kirigami.Heading {
            Layout.fillWidth: true
            level: 2
            text: name
        }

        Kirigami.Separator {
            Layout.fillWidth: true
            visible: description.length > 0
        }

        Controls.Label {
            Layout.fillWidth: true
            wrapMode: Text.WordWrap
            text: description
            visible: description.length > 0
        }
    }

    Controls.Button {
        Layout.alignment: Qt.AlignRight
        Layout.columnSpan: 2
        text: i18n("Edit")
    }
}

• Left, Kirigami.Heading : uses the ListElement's date as a level 1 heading.
• Middle, ColumnLayout: has a Kirigami.Heading that displays the task name; a Kirigami.Separator , which provides the horizontal line; and a Controls.Label , that displays a task's optional description. The latter two components have a visible property, which checks if the description is empty or not and displays the components depending on the result of description.length > 0.
• Right, Controls.Button : a button that will do something... soon!

Nuestra aplicación hasta ahora

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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.ApplicationWindow {
    id: root

    title: i18nc("@title:window", "Day Kountdown")

    // ListModel needed for ListView, contains elements to be displayed
    ListModel {
        id: kountdownModel
        // Each ListElement is an element on the list, containing information
        ListElement {
            name: "Dog birthday!!"
            description: "Big doggo birthday blowout."
            date: 100
        }
    }

    Component {
        id: kountdownDelegate
        Kirigami.AbstractCard {
            contentItem: Item {
                implicitWidth: delegateLayout.implicitWidth
                implicitHeight: delegateLayout.implicitHeight
                GridLayout {
                    id: delegateLayout
                    anchors {
                        left: parent.left
                        top: parent.top
                        right: parent.right
                    }
                    rowSpacing: Kirigami.Units.largeSpacing
                    columnSpacing: Kirigami.Units.largeSpacing
                    columns: root.wideScreen ? 4 : 2

                    Kirigami.Heading {
                        // Heading will be as tall as possible while respecting constraints
                        Layout.fillHeight: true
                        // Level determines the size of the heading
                        level: 1
                        text: date
                    }

                    // Layout for positioning elements vertically
                    ColumnLayout {
                        Kirigami.Heading {
                            Layout.fillWidth: true
                            level: 2
                            text: name
                        }
                        // Horizontal rule
                        Kirigami.Separator {
                            Layout.fillWidth: true
                            visible: description.length > 0
                        }
                        // Labels contain text
                        Controls.Label {
                            Layout.fillWidth: true
                            // Word wrap makes text stay within box and shift with size
                            wrapMode: Text.WordWrap
                            text: description
                            visible: description.length > 0
                        }
                    }
                    Controls.Button {
                        Layout.alignment: Qt.AlignRight
                        // Column spanning within grid layout (vertically in this case)
                        Layout.columnSpan: 2
                        text: i18n("Edit")
                        //onClicked: to be done...
                    }
                }
            }
        }
    }

    pageStack.initialPage: Kirigami.ScrollablePage {
        title: i18nc("@title", "Kountdown")

        // List view for card elements
        Kirigami.CardsListView {
            id: cardsView
            // Model contains info to be displayed
            model: kountdownModel
            // Delegate is how the information will be presented in the ListView
            delegate: kountdownDelegate
        }
    }
}

¡Así que ahí está nuestra tarjeta básica!

Con estos pasos hemos sentado las bases para añadir toda la funcionalidad a nuestra aplicación.