java - call method from fragment to fragment ( refresh adapter ) -

hello trying call function loadfiles() located in fragmentb , want call fragmenta, can refresh gridview images , videos.

i error same method

fatal exception: main     java.lang.nullpointerexception 

my method in fragmentb:

  public void loadfiles(){         gridview = (gridview) this.v.findviewbyid(r.id.grid);         file f = new file(home);         if (f.exists()){             string [] media = f.list();             arraylist<string> files = new arraylist<>();             (int i=0; i<media.length;i++){                 if (media[i].endswith(".jpg")||                         media[i].endswith(".png")||                         media[i].endswith(".jpeg")||                         media[i].endswith(".3gp")||                         media[i].endswith(".mp4")||                         media[i].endswith(".mov")){                     files.add(media[i]);                 }                  if (i==media.length-1){                     gridadapter adapter = new gridadapter(this.v.getcontext(), files, gridview);                     adapter.notifydatasetchanged();                     gridview.setadapter(adapter);                 }             }         }     } 

how call in fragmenta:

fragmentb b = new fragmentb(); b.loadfiles(); 

i think problem because of line have tried , there no luck :(

gridadapter adapter = new gridadapter(this.v.getcontext(), files, gridview); 

i suggest this:

 public class utils{  public static arraylist<string> loadfiles(){          file f = new file(home);         if (f.exists()){             string [] media = f.list();             arraylist<string> files = new arraylist<>();             (int i=0; i<media.length;i++){                 if (media[i].endswith(".jpg")||                         media[i].endswith(".png")||                         media[i].endswith(".jpeg")||                         media[i].endswith(".3gp")||                         media[i].endswith(".mp4")||                         media[i].endswith(".mov")){                     files.add(media[i]);                 }             }             return files;         }     } } 

now in fragmenta , fragmentb etc. can

  gridview = (gridview) this.v.findviewbyid(r.id.grid);      gridadapter adapter = new gridadapter(this.v.getcontext(), utils.loadfiles(), gridview);             gridview.setadapter(adapter);