Android: avoid multiple instances of the same activity?
<p>My app is capable of opening files from the Dropbox.  Currently, the following scenario occurs</p>

<ol>
<li>Open the Dropbox app from app drawer</li>
<li>Select a file in Dropbox, launch with my app</li>
<li>My app opens and displays the selected file</li>
<li>Hit home button.</li>
<li>Select my app from app drawer</li>
<li>My app opens and displays with no file displayed</li>
<li>Hit back, the empty version of my app closes and the version my app displaying the Dropbox file is now running</li>
</ol>

<p>If my app was launched from Dropbox, hitting home and launching my app from the app drawer should restore the running Activity (the one displaying the Dropbox file).  How can I accomplish this?</p>
