onAAScreenStateChanged
Called when Android Auto screen state changes.
This callback notifies the phone app which screen is currently active on AA, allowing the phone to show context-appropriate UI. This tracks the actual screen navigation on AA (map view, search, route preview, navigation).
The phone app should:
Update its UI to match the AA screen state
Show search UI when AA is in SEARCH state
Show route selection when AA is in ROUTE_PREVIEW state
Parameters
state
The new AA screen state