title: Android ViewPager: Update off-screen but cached fragments in ViewPager
body: <p>I have a ViewPager which contains several TextViews inside its fragment which they have different font sizes.
  In addition, I got buttons for increase/decreasing font size which calculate font size of each textView by adding its default size plus a value called STEP (which changes by inc/dec font size button). <br/>
  My problem is if a view is displayed for first time after applying size changes, It will create textViews in desired size during onCreateView() however if fragment was cached already and onCreateView is not called again, I don't know how to update their textViews considering only one of cached fragments is displaying on screen (and i can update it with no problem) but others are not displayed (I don't know if they are attached to activity or not in this case).<br/>
  In other words how can i detect which fragments are cached by ViewPager and their onCreateView already called (these are fragments which update to their views must be applied). I marked them in light green with question marks in below picture: <img src="https://i.stack.imgur.com/ufipl.png" alt="enter image description here"></p>