title: Filtering a list in different activities
body: <p>I have an app where a main activity generates a list, and in the main activity there are many tabs that filter the list and lists a subset of the entire list in a customized ListView with checkboxes.</p>
  
  <p>I have adapters in each of the tabs, and have threads running in the various onCreate()s that filter the main list and add the relevant subset into its own adapter. I'm saving the checkbox status into a SharedPreferences everytime the use checks a box.</p>
  
  <p>I'm having a problem synchronizing the checkboxes among the various ListActivities. When I check a box in 1 ListActivity and switch to another tab, it doesn't update there. Only when I exit the app and restart it does the main activity re-generate the list, read the SharedPreferences and update all the checkboxes.</p>
  
  <p>How do I have this done instantaneously so that the various ListActivities of the various tabs are always synchronized?</p>
  
  <p>Thanks.</p>