getReferrer

Return information about who launched this activity. If the launching Intent contains an Intent.EXTRA_REFERRER, that will be returned as-is; otherwise, if known, an android-app: referrer URI containing the package name that started the Intent will be returned. This may return null if no referrer can be identified -- it is neither explicitly specified, nor is it known which application package was involved.

If called while inside the handling of onNewIntent, this function will return the referrer that submitted that new intent to the activity. Otherwise, it always returns the referrer of the original Intent.

Note that this is not a security feature -- you can not trust the referrer information, applications can spoof it.