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Example Application:
Node Class Reference: MarkupList

The MarkupList node class provides a customizable list that can include multiple graphic images and labels, in virtually any type of design and configuration for the list items.

For example, is a list where each item has two graphic images (an icon and a small poster image), a label, and a custom underline focus indicator:

The method to configure a custom list like this is to have a separate component definition of the appearance and behavior of the list items. The name of this component is set as the itemComponentName field value of the MarkupList node. Then as the user moves focus to an individual item in the list, the appearance and behavior of the item is configured according to the item component scripting. In the example, as each item is focused, the red underline focus indicator appears, along with the small poster image. The icon, label, and small poster image for each item are contained in the ContentNode node set as the content field value of the MarkupList node, the same way the graphic images and other content meta-data are set in PosterGrid Markup.

In markuplistscene.xml, we define the basic dimensions and configuration of the MarkupList node in the <children> element in a way that is similar to how lists and grids were defined in LabelList Markup and PosterGrid Markup. In addition to the itemComponentName field where we set name of the component with the list item configuration, we set the itemSize field (similar to the basePosterSize field of a PosterGrid node) and the itemSpacing field (identical to the PosterGrid node itemSpacing field):



Then we set the drawFocusFeedback field to false, since we will be using a custom underline focus indicator, and set vertFocusAnimationStyle to floatingFocus (again, these fields are the same as in the LabelList node and several other list and grid nodes).

Now let's look at markuplistitem.xml, which is the list item configuration component file:

MarkupList Item Component Example  Expand source

The <children> element of markuplistitem.xml contains the renderable nodes that will be in each list item. It's a typical markup for renderable nodes as described in Renderable Node Markup, except for a couple of things. Note that we don't supply a uri field value for the Poster nodes, or a text field value for the Label node. We do provide an ID for each renderable node, because we intend to supply the missing field values in the <script> element using BrightScript.

As the ContentNode node for the list is set, and a user moves focus to an item in the list, the <interface> element fields are updated by the MarkupList node to the value for that item. So to script the custom appearance and behavior of the list items, we set observers on the relevant <interface> fields using the onChange attribute to identify the callback functions triggered by the field value change:

When the ContentNode node for the list is set, the itemContent field value change triggers the showcontent() callback function, and focusPercent field value change triggers the showfocus() callback function. The showcontent() callback function sets the URL of the each item icon and the small poster image, and the text of the item label, according the attributes in the child ContentNode node for the item:

Then the showfocus() callback function makes visible the custom red underline focus indicator and the small poster image when the item is focused:

The showfocus() callback function makes use of the focusPercent field value, which varies from 0 to 1.0 as focus moves to the item, and from 1.0 to 0 as focus leaves the item. Since this varying value has the identical range as the key field range of an Animation node (see Animation Markup), this field value can be used as an animation "key" to smoothly "fade" in and out an item element as focus moves to and from the item. In this example, we key the cursor and small poster image opacity to the value of the focusPercent field.

This method of creating a custom list or grid item appearance is used in the MarkupGrid and RowList nodes too, so spend a little time now to understand how it works... 

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