How to use the Feathers ScrollBar component

The ScrollBar component displays a numeric value between a minimum and maximum. The value may be changed by sliding a thumb along a track in either a horizontal or a vertical direction. A scroll bar also has a button on each side of the track that adjusts the value by a small step when triggered. This component is designed to be used with components that support scrolling, like ScrollContainer and List.

The Basics

You can use the ScrollBar with a class like ScrollContainer or List by instantiating it in the horizontalScrollBarFactory or the verticalScrollBarFactory.

list.horizontalScrollBarFactory = function():IScrollBar
{
    return new ScrollBar();
}

The container will automatically handle setting properties like direction, minimum, maximum, and step, and it will automatically listen for Event.CHANGE to know when the value property changes.

Skinning a ScrollBar

The skins for a ScrollBar control are divided into several parts, including the thumb, the track(s), and the increment and decrement buttons. For full details about what skin and style properties are available, see the ScrollBar API reference.

Targeting a ScrollBar in a theme

If you are creating a theme, you can set a function for the default styles like this:

getStyleProviderForClass( ScrollBar ).defaultStyleFunction = setScrollBarStyles;

If you want to customize a specific scroll bar to look different than the default, you may use a custom style name to call a different function:

scrollBar.styleNameList.add( "custom-scroll-bar" );

You can set the function for the custom style name like this:

getStyleProviderForClass( ScrollBar )
    .setFunctionForStyleName( "custom-scroll-bar", setCustomScrollBarStyles );

Trying to change the scroll bar's styles and skins outside of the theme may result in the theme overriding the properties, if you set them before the scroll bar was added to the stage and initialized. Learn to extend an existing theme to add custom skins.

If you aren't using a theme, then you may set any of the scroll bar's properties directly.

Skinning the Thumb

This section only explains how to access the thumb sub-component. Please read How to use the Feathers Button component for full details about the skinning properties that are available on Button components.

With a Theme

If you're creating a theme, you can target the ScrollBar.DEFAULT_CHILD_STYLE_NAME_THUMB style name.

getStyleProviderForClass( Button )
    .setFunctionForStyleName( ScrollBar.DEFAULT_CHILD_STYLE_NAME_THUMB, setScrollBarThumbStyles );

You can override the default style name to use a different one in your theme, if you prefer:

scrollBar.customThumbStyleName = "custom-thumb";

You can set the function for the customThumbStyleName like this:

getStyleProviderForClass( Button )
    .setFunctionForStyleName( "custom-thumb", setScrollBarCustomThumbStyles );

Without a Theme

If you are not using a theme, you can use thumbFactory to provide skins for the scroll bar's thumb:

scrollBar.thumbFactory = function():Button
{
    var button:Button = new Button();
    //skin the thumb here
    button.defaultSkin = new Image( upTexture );
    button.downSkin = new Image( downTexture );
    return button;
}

Alternatively, or in addition to the thumbFactory, you may use the thumbProperties to pass skins to the thumb.

scrollBar.thumbProperties.defaultSkin = new Image( upTexture );
scrollBar.thumbProperties.downSkin = new Image( downTexture );

In general, you should only pass skins to the scroll bar's thumb through thumbProperties if you need to change skins after the thumb is created. Using thumbFactory will provide slightly better performance, and your development environment will be able to provide code hinting thanks to stronger typing.

Track(s) and Layout

The scroll bar's track is made from either one or two buttons, depending on the value of the trackLayoutMode property. The default value of this property is ScrollBar.TRACK_LAYOUT_MODE_SINGLE, which creates a single track that fills the entire width and height of the scroll bar.

If we'd like to have separate buttons for both sides of the track (one for the minimum side and another for the maximum side), we can set trackLayoutMode to ScrollBar.TRACK_LAYOUT_MODE_MIN_MAX. In this mode, the width or height of each track (depending on the direction of the scroll bar) is adjusted as the thumb moves to ensure that the two tracks always meet at the center of the thumb.

ScrollBar.TRACK_LAYOUT_MODE_SINGLE is often best for cases where the track's appearance is mostly static. When you want down or hover states for the track, ScrollBar.TRACK_LAYOUT_MODE_MIN_MAX works better because the state will only change on one side of the thumb, making it more visually clear to the user what is happening.

When the value of trackLayoutMode is ScrollBar.TRACK_LAYOUT_MODE_SINGLE, the scroll bar will have a minimum track, but it will not have a maximum track. The minimum track will fill the entire region that is scrollable.

Skinning the Minimum Track

This section only explains how to access the minimum track sub-component. Please read How to use the Feathers Button component for full details about the skinning properties that are available on Button components.

With a Theme

If you're creating a theme, you can target the ScrollBar.DEFAULT_CHILD_STYLE_NAME_MINIMUM_TRACK style name.

getStyleProviderForClass( Button )
    .setFunctionForStyleName( ScrollBar.DEFAULT_CHILD_STYLE_NAME_MINIMUM_TRACK, setScrollBarMinimumTrackStyles );

You can override the default style name to use a different one in your theme, if you prefer:

scrollBar.customMinimumTrackStyleName = "custom-minimum-track";

You can set the function for the customMinimumTrackStyleName like this:

getStyleProviderForClass( Button )
    .setFunctionForStyleName( "custom-minimum-track", setScrollBarCustomMinimumTrackStyles );

Without a Theme

If you are not using a theme, you can use minimumTrackFactory to provide skins for the scroll bar's minimum track:

scrollBar.minimumTrackFactory = function():Button
{
    var button:Button = new Button();
    //skin the minimum track here
    button.defaultSkin = new Image( upTexture );
    button.downSkin = new Image( downTexture );
    return button;
}

Alternatively, or in addition to the minimumTrackFactory, you may use the minimumTrackProperties to pass skins to the minimum track.

scrollBar.minimumTrackProperties.defaultSkin = new Image( upTexture );
scrollBar.minimumTrackProperties.downSkin = new Image( downTexture );

In general, you should only pass properties to the scroll bar's minimum track through minimumTrackProperties if you need to change these values after the minimum track is created. Using minimumTrackFactory will provide slightly better performance, and your development environment will be able to provide code hinting thanks to stronger typing.

Skinning the Maximum Track

This section only explains how to access the maximum track sub-component. Please read How to use the Feathers Button component for full details about the skinning properties that are available on Button components.

The scroll bar's maximum track may be skinned similarly to the minimum track. The style name to use with themes is ScrollBar.DEFAULT_CHILD_STYLE_NAME_MAXIMUM_TRACK or you can customize the style name with customMaximumTrackStyleName. If you aren't using a theme, then you can use maximumTrackFactory and maximumTrackProperties.

Skinning the Decrement Button

This section only explains how to access the decrement button sub-component. Please read How to use the Feathers Button component for full details about the skinning properties that are available on Button components.

With a Theme

If you're creating a theme, you can target the ScrollBar.DEFAULT_CHILD_STYLE_NAME_DECREMENT_BUTTON style name.

getStyleProviderForClass( Button )
    .setFunctionForStyleName( ScrollBar.DEFAULT_CHILD_STYLE_NAME_DECREMENT_BUTTON, setScrollBarDecrementButtonStyles );

You can override the default style name to use a different one in your theme, if you prefer:

scrollBar.customDecrementButtonStyleName = "custom-decrement-button";

You can set the function for the customDecrementButtonStyleName like this:

getStyleProviderForClass( Button )
    .setFunctionForStyleName( "custom-decrement-button", setScrollBarCustomDecrementButtonStyles );

Without a Theme

If you are not using a theme, you can use decrementButtonFactory to provide skins for the scroll bar's decrement button:

scrollBar.decrementButtonFactory = function():Button
{
    var button:Button = new Button();
    //skin the decrement button here
    button.defaultSkin = new Image( upTexture );
    button.downSkin = new Image( downTexture );
    return button;
}

Alternatively, or in addition to the decrementButtonFactory, you may use the decrementButtonProperties to pass skins to the decrement button.

scrollBar.decrementButtonProperties.defaultSkin = new Image( upTexture );
scrollBar.decrementButtonProperties.downSkin = new Image( downTexture );

In general, you should only pass properties to the scroll bar's decrement button through decrementButtonProperties if you need to change these values after the decrement button is created. Using decrementButtonFactory will provide slightly better performance, and your development environment will be able to provide code hinting thanks to stronger typing.

Skinning the Increment Button

This section only explains how to access the increment button sub-component. Please read How to use the Feathers Button component for full details about the skinning properties that are available on Button components.

The scroll bar's increment button may be skinned similarly to the decrement button. The style name to use with themes is ScrollBar.DEFAULT_CHILD_STYLE_NAME_INCREMENT_BUTTON or you can customize the style name with customIncrementButtonStyleName. If you aren't using a theme, then you can use incrementButtonFactory and incrementButtonProperties.