From the Android AsyncTask doc:
"The task instance must be created on the UI thread.", and
"execute(Params...) must be invoked on the UI thread."
So I think the answer to your first question is "no". As far as the second, those methods are all invoked on the UI thread, but it's a bit moot.
EDIT: I'm not sure if those are absolute restrictions, or strong suggestions, but in both cases, I'd recommend following them.
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