Load Images probelm from url in Android -

i trying load images url , set in gridview, when scroll screen images changes. beginner in android. don't know problem in code. here code..

public class photos extends activity {  public static final string tag_image_name = "image_name"; public static final string tag_image_thumb_name = "image_thumb_name"; public static string url = "http://...../..../..../mainapi.php";  arraylist<hashmap<string, string>> photolist; string responsedata = null; static gridview gridview;  @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.photos);      gridview = (gridview)findviewbyid(r.id.gridview);     photolist = new arraylist<hashmap<string,string>>();     new asyncdata().execute();      gridview.setonitemclicklistener(new onitemclicklistener() {          @override          public void onitemclick(adapterview<?> parent, view v, int position, long id) {                  // sending image id fullscreenactivity                 intent = new intent(getapplicationcontext(), fullimage.class);                 // passing array index                 i.putextra("imagename", tag_image_name);                 startactivity(i);             }     }); }  class asyncdata extends asynctask<string, void, void> {     progressdialog pdialog;      @override     protected void onpreexecute() {         pdialog = new progressdialog(photos.this);         pdialog.settitle("loading....");         pdialog.setmessage("please wait...");         pdialog.show();         super.onpreexecute();     }      @override     protected void doinbackground(string... args) {         // todo auto-generated method stub         httpclient httpclient = new defaulthttpclient();         httppost httppost = new httppost(url);         try {             list<namevaluepair> namevaluepairs = new arraylist<namevaluepair>();             namevaluepairs.add(new basicnamevaluepair("rquest","{\"method\":\"photogallery\",\"body\":[{}]}"));             httppost.setentity(new urlencodedformentity(namevaluepairs, http.utf_8));             httpresponse response = httpclient.execute(httppost);             httpentity resentity = response.getentity();             responsedata = entityutils.tostring(resentity);             try {                 jsonarray data = new jsonarray(responsedata);                 (int = 0; < data.length(); i++) {                     hashmap<string, string> map = new hashmap<string, string>();                     jsonobject c = data.getjsonobject(i);                     string photoname = c.getstring(tag_image_name);                     string imagethumbname = c.getstring(tag_image_thumb_name);                     map.put(tag_image_name, photoname);                     map.put(tag_image_thumb_name, imagethumbname);                     photolist.add(map);                 }              } catch (jsonexception e) {                 // todo: handle exception                 e.printstacktrace();             }         } catch (clientprotocolexception e) {             e.printstacktrace();         } catch (ioexception e) {             e.printstacktrace();         }         return null;      }      protected void onpostexecute(void result) {         super.onpostexecute(result);         gridview.setadapter(new photosadapter(photos.this, r.layout.photo_row, photolist));         if (pdialog != null && pdialog.isshowing()) {             pdialog.dismiss();         }     } }  @override public boolean onkeydown(int keycode, keyevent event) {     if(keycode == keyevent.keycode_back && event.getrepeatcount() == 0)     {         finish();         return true;     }     return super.onkeydown(keycode, event);   } } 

phgotosadapter class

public class photosadapter extends arrayadapter<hashmap<string, string>>{ context context; string uri; bitmap bitmap; arraylist<hashmap<string, string>> mylist; hashmap<string, string> mydata; int layout; public photosadapter(context context, int textviewresourceid, list<hashmap<string, string>> objects) {     super(context, textviewresourceid, objects);     // todo auto-generated constructor stub     this.context = context;     this.mylist = (arraylist<hashmap<string, string>>) objects;     this.layout = textviewresourceid; }  @override  public view getview(int position, view convertview, viewgroup parent)  {     // todo auto-generated method stub     view row = null;     layoutinflater inflater = ((activity) context).getlayoutinflater();     row = inflater.inflate(layout, parent, false);     mydata = mylist.get(position);     imageview image = (imageview)row.findviewbyid(r.id.imagephoto);       try{         imagedownloadtask task = new imagedownloadtask(image);         task.execute();         uri = "" + mydata.get(photos.tag_image_thumb_name).replace(" ", "%20");         image.setimagebitmap(bitmap);         image.setscaletype(imageview.scaletype.center_inside);     } catch (exception e) {         // todo: handle exception         e.printstacktrace();     }     return row; } public static bitmap getbitmapfromurl(string src) {     try {         url url = new url(src);         httpurlconnection connection = (httpurlconnection) url.openconnection();         connection.setdoinput(true);         connection.connect();         inputstream input = connection.getinputstream();         bitmap mybitmap = bitmapfactory.decodestream(input);         return mybitmap;     } catch (ioexception e) {         e.printstacktrace();         return null;     } }  class imagedownloadtask extends asynctask<void, integer, bitmap> {     private imageview mview;     progressdialog pdialog;     imagedownloadtask(imageview view){         mview = view;     }      @override     protected bitmap doinbackground(void... params) {         try {             bitmap =  getbitmapfromurl(uri);         } catch (exception e) {             // todo auto-generated catch block             e.printstacktrace();         }         return bitmap;     }     @override     protected void onpostexecute(bitmap result) {        mview.setimagebitmap(result);      }   } } 

i don't know problem in it, please me , give solution.

imageloader imageloader; imageloader=new imageloader(context.getapplicationcontext()); imageloader.displayimage(urlname, imageviewname); try