title: Call a UIViewController method when application goes background and come to foreground
body: <p>how to call a method when application goes background and changes some activity like the time or date of mobile and come to foreground (application active mode).</p>
  
  <p>Then i want to call a method in UIViewController classes</p>
  
  <p>FirstViewController Class Method.</p>
  
  <pre><code>-(void)refreshItems{
  // Your item refresh code.
  }
  </code></pre>