How to change the background of multiple activities at the same time?
<p>I am developing an app with 3 activities. Every activity has the same background. I want to enable the users to change the background of all the three activities. So i used a AlertDialog to provide the user several choices. When the user click the items on the Dialog, the background will be changed.</p>

<p>I have tried two ways of implementing this function above:</p>

<p>1) use the Android:theme in AndroidManifest.XML. This really worked. But the bad thing was that all the View in the application will extend the theme. I made the background of unrelated views null. But i can not remove extended theme in the Dialog. This made my dialog very ugly. </p>

<p>2) I applied 'style' in the layout xml of the three activity. But the problem is that i can not modify the background attribute in the style programmatically. </p>

<p>Does someone have some idea to deal with this problem? thx! </p>
