how to secure a app to make a closed beta in android?
<p>i need to know how can i secure my app to make a close beta?</p>

<p>i want to send my app to some people so that they can test it. but i dont want them to share the .apk with other people and just use it some days. so i need to implement some kind of trial/beta mode.</p>

<p>i need something, that the app e.g. only runs 7 days or so. how to do this?</p>
