Knobs and Controls
Vehicles that support CarPlay have physical controls (buttons, knobs, and touchpads, for example) that supplement the touchscreen and, in some cases, serve as the primary means of user input. At minimum, a Siri button, navigation controls, selection controls, and back controls are always present when physical controls provide the primary means of user input.
Respond to media controls as expected. If your app offers audio playback features, it should respond when the user presses a physical play, pause, next track, previous track, fast forward, and rewind button in the car. For developer guidance, see MPRemoteCommandCenter.
CarPlay has a focus model that helps people move through onscreen interface elements using a knob or touchpad when the built-in display doesn’t support touch interactions. By rotating a knob or swiping a touchpad, focus moves from element to element, stopping on a specific one. The user can then press the knob, tap the touchpad, or press a button to activate or interact with the element.
Position onscreen elements so the user can navigate logically from item to item. Changes in focus should be predictable.
For developer guidance, see UIFocusEnvironment.