title: change the background image in gallery
body: <p>i shows a buttons in gallery view for scrolling purpose. if i clicked one button(ex:button1) then change the button1 background and then i clicked another button(ex:button2) then change the background of the button2 and also get the previous background of the button1. So please tell me how to change the background in gallery.</p>
  
  <p>Best Regards.</p>
  
  <p>Thank you in advance.</p>