how to place a cliackable overlay on top of another activity in android?

i need to place a view on top of another activity which should have clickable buttons etc. the underlying activity itself MUST NOT be stopped/paused or else.

to be more specific: i want to display some kind of a note when i receive a call. this note should be displayed on top of the incoming-call-activity without d开发者_如何转开发isrupting the activity itself or hindering the user from interacting with it...

how do i do this?

Could using an AlertDialog help perhaps?