At a portable electronic device that includes a portable-device display and is in communication with a vehicle display, displaying a first user interface on the portable-device display. Sending, from the portable electronic device to the vehicle display, information for generating a second user interface, the second user interface including an affordance. While the second user interface is displayed on the vehicle display, detecting an input activating the affordance in the second user interface, and in response, causing the portable electronic device to invoke a digital assistant. In response to invoking the digital assistant, prompting a user for an audible request. In response to receiving the audible request, causing display, within the second user interface, of a digital assistant dialogue box; and subsequently causing display, within the second user interface, of a user interface object associated with a search result, and maintaining the first user interface on the portable-device display.