Display dialog of type TYPE_SYSTEM_DIALOG

[kh]

HI,

I want to display TYPE_SYSTEM_DIALOG from a service:
snapshot of code:
popup.getWindow().setType(WindowManager.LayoutParams.TYPE_SYSTEM_DIALOG);
popup.show();

Basically I am finding a way to display dialog without an activity. I found that TYPE_SYSTEM_DIALOG could be a way. But the dialog doesn't show up and there is no error. The code with normal dialog using an activity shows up, but not system dialog from service.
My service can be a system service(system app).
So my question is:
- what permissions do I need to set ?
- is there anything else I need to do ? or call ?
- anything i would be missing which is needed for TYPE_SYSTEM_DIALOG

(This question might fit in android developers but I think normal developers wouldn't use TYPE_SYSTEM_DIALOG, so posting here)

thank you.