android - New to java - Attempt to invoke virtual method 'void -

i new coding , java , got problem , wasn't able fix it. strange thing error happens on android 5.

below error message

java.lang.nullpointerexception: attempt invoke virtual method 'void com.nostra13.universalimageloader.core.imageloader.displayimage(java.lang.string, android.widget.imageview, com.nostra13.universalimageloader.core.displayimageoptions)' on null object reference @ com.fragments.activity.storeactivity$1.onmgarrayadaptercreated(storeactivity.java:143) @ com.adapters.mgarrayadapter.getview(mgarrayadapter.java:82) 

storeactivity.java

public void onmgarrayadaptercreated (mgarrayadapter adapter, view v, int position, viewgroup viewgroup, object obj){     // todo auto-generated method stub      final store store = arraydata.get(position);      photo p = q.getphotobystoreid(store.getstore_id());      mgimageview imgviewphoto = (mgimageview) v.findviewbyid(r.id.imgviewphoto);     imgviewphoto.setcornerradius(0.0f);     imgviewphoto.setborderwidth(uiconfig.border_width);     imgviewphoto.setbordercolor(getresources().getcolor(uiconfig.theme_black_color));     imgviewphoto.setonclicklistener(new onclicklistener() {          @override         public void onclick(view arg0) {             // todo auto-generated method stub             intent = new intent(storeactivity.this, detailactivity.class);             i.putextra("store", store);             storeactivity.this.startactivity(i);         }     });      if (p != null) {         mainactivity.getimageloader().displayimage(p.getphoto_url(), imgviewphoto, options);     }     else {         imgviewphoto.setimageresource(uiconfig.slider_placeholder);     } } 

mgarrayadapter.java

public class mgarrayadapter extends baseadapter {      private context c;     private int resid;     private onmgarrayadapterlistener mcallback;     public list<object> objects;      public interface onmgarrayadapterlistener {         public void onmgarrayadaptercreated(mgarrayadapter adapter, view v, int position, viewgroup viewgroup, object obj);     }      public void setonmgarrayadapterlistener(onmgarrayadapterlistener listener) {         try {             mcallback = (onmgarrayadapterlistener) listener;         }         catch (classcastexception e) {             throw new classcastexception(this.tostring() + " must implement onmgarrayadapterlistener");         }     }      public mgarrayadapter(context c, arraylist<object> objects, int resid) {         this.c = c;         this.objects = objects;         this.resid = resid;     }      @override     public int getcount() {         // todo auto-generated method stub         return objects.size();     }      @override     public object getitem(int pos) {         // todo auto-generated method stub         return objects.get(pos);     }      @override     public long getitemid(int pos) {         // todo auto-generated method stub         return pos;     }      @override     public view getview(int pos, view v, viewgroup viewgroup) {         // todo auto-generated method stub          viewholder viewholder = null;          if (v == null) {             layoutinflater li = (layoutinflater) c.getsystemservice(context.layout_inflater_service);             v = li.inflate(resid, null);              viewholder = new viewholder();             viewholder.view = v;             v.settag(viewholder);         }         else {             viewholder = (viewholder) v.gettag();             log.w("mglistadapter class", "view being reused.");         }          if (mcallback != null)             mcallback.onmgarrayadaptercreated(this, viewholder.view, pos, viewgroup, objects.get(pos));          return v;     }      public class viewholder {         public view view;     }      public void add(object obj) {         if (objects == null)             objects = new arraylist<object>();          objects.add(obj);     }      public void clearall() {         if (objects == null)             objects = new arraylist<object>();          objects.clear();     } } 

why not try:

public void add(object obj) {      if(objects == null)         objects = new arraylist<object>();      objects.add(obj); }  public void clearall(object obj) {      if(objects == null)         objects = new arraylist<object>();      objects.clear(); }