I think the EASIEST path might be to overlay your main function view with a standard view that is black, and then use the alpha property to let your main view go, then ImageView or something like that again on top of the alpha mixed view.
Of course, there are other ways to do this, but it MAY be the easiest.
Alternatively, you can have one image that appears, whose background is already translucent, then you could potentially only need an image, and not a second view (as indicated above).
Depending on what type of layout you are using, you may have to do it as a popper so that it can really be laid out on top instead of linearly laid out or relatively laid out, etc.