title: How does instagram fixed and change the bar when scroll up in android?
body: <p><strong>Notice:</strong> I cannot provide pictures due to my reputation.</p>
  
  <p>When we scroll down from the feed in instagram the action bar is actually hide and a white bar that indicate the user name and time is fixed at the top. When we scrolling down again the previous white bar will scroll up and next bar will fixed at the top again. I want to make something like that for my school project.</p>
  
  <p>So my first question is how can I hide the action bar while scrolling up and show it again while i scrolling down?</p>
  
  <p>Second question is how can I make the white bar just like how instagram did it?</p>
  
  <p>Any help will be highly apperciate!! </p>