title: Open PreferenceActivity using virtual button?
body: <p>I'm quite new to android develompent and I'm trying to figure out how to take users to my <code>PreferenceActivity</code>. I already created a Preferences class with it's corresponding layout however I cannot figure out how to take users to this Activity on phones without a physical menu button. </p>
  
  <p>I'm using a Nexus 4 and it doesn't even have a physical menu button. I've seen the menu button (three vertical dots) pop up now and then on the virtual buttons (bottom right), how can I make that button appear on the phone and take users to settings onkeydown?</p>