title: Single alert dialog for entire application
body: <p>I have to display many error messages and alert dialogues in my application.
  I do not want to use Toast, I prefer to use <code>AlertDialog</code>.</p>
  
  <p>Instead of creating a new alert dialog in every activity, how do I create and maintain one alert dialog and just change the error message string in it?</p>
  
  <p>Whatever activity I am in, I must be able to access the <code>AlertDialog</code> instance to show and dismiss it.</p>
  
  <p>How can I achieve this? Kindly give me some lead on this.</p>