Long-tap to see tooltips is a convention that has been proposed in various incarnations of the Android UI guidelines. The convention was present in very early A

Long-tap to see tooltips is a convention that has been proposed in various incarnations of the Android UI guidelines. The convention was present in very early Android UI guidelines (e.g. Android 4.x); I'm not sure if it still is. The problem is that long-tap gets used for a lot of other things on Android (extended selection, particularly). The user experience is pretty unhappy if you use both conventions. And, in practice, long-tap tooltips are so rarely provided on Android apps that I doubt that ordinary users would expect them at all. As far as I know, tap-and-hold (as distinguished from long-tap) isn't a conventional gesture on Android.