Keyboard focus management in Feathers (Starling version)

In desktop apps, users expect to be able to use the Tab key to navigate between focusable UI components, and they expect to be able to use the keyboard to do things like press buttons or adjust sliders. On smart TVs, the remote typically provides a d-pad or another input method for passing focus up, down, to the left, or to the right.

Feathers provides optional focus management support with the FocusManager class. Typically, you can enable the FocusManager when your app starts up, and it will "just work". However, there are ways to customize the focus behavior if your app has special requirements.

The example themes enable focus management automatically on both desktop and mobile.

Enabling the Focus Manager

To enable focus management, only one line is required when your app first starts up:

FocusManager.setEnabledForStage( this.stage, true );

That's it! You will be able to use Tab and Shift+Tab to navigate between focusable components in your app when using a keyboard, or you can use the d-pad on a smart TV remote. Some platforms will also dispatch appropriate d-pad events when using a game controller.

If you are building an AIR desktop app with multiple Starling instances in multiple windows, you will need to enable focus management for each stage with separate calls to setEnabledForStage().

Changing Focus Programmatically

You can manually tell the FocusManager to change which component is current focused:

var focusManager:IFocusManager = FocusManager.getFocusManagerForStage( this.stage );
focusManager.focus = button;

It's as simple as setting the focus property on the IFocusManager.

To clear focus so that no component is focused, set this property to null:

var focusManager:IFocusManager = FocusManager.getFocusManagerForStage( this.stage );
focusManager.focus = null;

Customizing focus order

By default, when the user changes focus with Tab or Shift+Tab on the keyboard, Feathers will pass focus using display list ordering. With getChildIndex() and other standard display list APIs, the focus manager will search the display list in a generally intuitive order to find the next (or previous) child that can receive focus.

If things end up a bit out of the ordering that you expected, you can customize the focus order using the nextTabFocus and previousTabFocus properties:

var button1:Button = new Button();
this.addChild( button1 );
var button2:Button = new Button();
this.addChild( button2 );
button1.nextTabFocus = button2;
button2.previousTabFocus = button1;

When using a d-pad to change focus, the focus manager uses special heuristics to determine which component should be given focus next, based on which direction is chosen (up, down, left, or right).

If needed, you may customize the focus order for d-pad using the nextUpFocus, nextDowbFocus, nextLeftFocus, and nextRightFocus properties.

Focus and pop-Ups

The focus manager and the pop-up manager know how to communicate. If a pop-up is modal, a new focus manager will be created and it will gain exclusive control over keyboard focus. Until the modal pop-up is closed, nothing below the modal overlay will be able to receive focus. Multiple modal pop-ups will add additional focus managers to the stack that will ensure that each modal layer blocks keyboard focus to anything below.

If a pop-up is not modal, then the same focus manager will remain active and everything will be able to receive focus, including the pop-up and everything below the pop-up.