basic information about holder in android -

i'm searching information "holder" in android...because i've seen code used in using checkbox in gridview...but couldn't find basic information it. i'll happy if can me. here part of code used holder :

public view getview(int position, view convertview, viewgroup parent) {             viewholder holder;             if (convertview == null) {                 holder = new viewholder();                 convertview = minflater.inflate(                         r.layout.galleryitem, null);                 holder.imageview = (imageview) convertview.findviewbyid(r.id.thumbimage);                 holder.checkbox = (checkbox) convertview.findviewbyid(r.id.itemcheckbox);                  convertview.settag(holder);             }             else {                 holder = (viewholder) convertview.gettag();             }             holder.checkbox.setid(position);             holder.imageview.setid(position); 

your code might call findviewbyid() during scrolling of listview, can slow down performance. when adapter returns inflated view recycling, still need elements , update them. way around repeated use of findviewbyid() use "view holder" design pattern.

a viewholder object stores each of component views inside tag field of layout, can access them without need them repeatedly.

for more info refer here