How to access a custom ButtonBar button?

I've created a custom Spark ButtonBar. I'd like to show notification badges in it (i.e. a number showing how many notifications that tab has), but I can't figure out how to access the button externally.

I've looked at questions like this one: Hide a Button in a ButtonBar

But that doesn't seem to work, the object I get back from:

btnBarNav.dataGroup.getElementAt(0);

is not an instance of Button or my skin, it's a "GameMenuBarInnerClass0".

Any suggestions on how best to pass some data to my skin to show a number related to the button?

Solution

Don't try to access and manipulate the view (your Buttons) directly. Use a model + data binding instead.

Create a custom skin

Looks like you already did this, but just for reference: you'll need a custom skin for ButtonBar, and three skins for the ButtonBarButtons: one for the first button, one for the last and one that will apply to all buttons in between.

Use presentation models for dataprovider

Create a presentation model that holds a label for the button, perhaps an icon and whatever additional information you'll require in the button. For example:

class ButtonModel {
    public var label:String;
    [Bindable]
    public var messageCount:int = 0;
}

Note that I made messageCount bindable so that we can bind to it later.

Assign a collection of these models as dataprovider of the ButtonBar

<s:ButtonBar>
    <s:ArrayList>
        <rs:ButtonModel label="Button 1"/>
        <rs:ButtonModel label="Button 2"/>
    </s:ArrayList>
</s:ButtonBar>

Use presentation properties in the custom skin

In your custom button skin, you can now bind to the properties of this presentation model. The hostcomponent (ButtonBarButton) has a property data that holds this model instance.

<s:Label id="labelDisplay"/>
<s:Label text="{hostComponent.data.messageCount}"/>

Whenever you update the messageCount property on the model, it will automatically be reflected in the button.