title: Selecting all Items in a ListView - ActionMode
body: <p>I have an ListView that has ActionMode features implemented. Long-pressing any list item brings up the contextual ActionMode. And it has multi-select and all that. What I'm trying to do is and cannot figure out how to is select all items in the list view by pressing one button. I'm not sure how exactly to do that. </p>
  
  <p>Pressing the button next to the trashcan (the 4 square one should highlight and select all list items - carrots, onions and Greek Yogurt.</p>
  
  <p><img src="https://i.imgur.com/SsyuJQFm.png" alt="Here is a screenshot of my app"> </p>