multithreading - Why am I getting null pointer in the getGraphObject when trying to post a image to facebook from android? -

i trying post photo url facebook. so, have method converts image located in provided url bitmap, after want publish image facebook photos of user. code:

method converts image located in url bitmap image:

public bitmap downloadimage(string url) {    bitmap bm = null;    try {        url aurl = new url(url);        urlconnection conn = aurl.openconnection();        conn.connect();        inputstream = conn.getinputstream();        bufferedinputstream bis = new bufferedinputstream(is);        bm = bitmapfactory.decodestream(bis);        bis.close();        is.close();    } catch (ioexception e) {        log.e("hub","error getting image server : " + e.getmessage().tostring());    }     return bm; } 

this try post image in facebook:

private void posttofacebook(byte[] data) {    session session = session.getactivesession();     if (session != null) {         bundle postparams = new bundle();        postparams.putstring("caption", "teste caption");        postparams.putbytearray("picture", data);         request.callback callback = new request.callback() {            public void oncompleted(response response) {                jsonobject graphresponse = response.getgraphobject().getinnerjsonobject();                string postid = null;                try {                    postid = graphresponse.getstring("id");                } catch (jsonexception e) {                    log.i("", "json error "+ e.getmessage());                }                facebookrequesterror error = response.geterror();                if (error != null) {                    toast.maketext(getcontext(), error.geterrormessage(), toast.length_short).show();                    } else {                        toast.maketext(getcontext(), postid, toast.length_long).show();                }            }        };             request request = new request(session, "me/photos", postparams, httpmethod.post, callback);         requestasynctask task = new requestasynctask(request);        task.execute();    } else {     toast.maketext(getcontext(), "not logged", toast.length_short).show();    } 

but @ line: response.getgraphobject(), getting null pointer exception. i've tried execute in background thread, this:

class convertimagetask extends asynctask<url, integer, byte[]> { asynctask<params,progress,result> @override protected void onpreexecute() {     super.onpreexecute(); // nothing here }  @override protected byte[] doinbackground(url... params) { byte[] data;     bitmap bi = downloadimage(getphotourl());     bytearrayoutputstream baos = new bytearrayoutputstream();     bi.compress(bitmap.compressformat.png, 100, baos);     data = baos.tobytearray(); return data; } @override protected void onpostexecute(byte[] result) {     posttofacebook(result); } 

but error continues.

how can fix this? thank you!

the pages i've gone through show "picture" parameter url, not data can upload computer.

to upload photo using:

request request = request.newuploadphotorequest(session.getactivesession(),                   bitmapfactory.decodestream(this.getassets().open("yourfile.png")),                new request.callback(){              @override             public void oncompleted(response response) {                 facebookrequesterror error = response.geterror();                 if(error != null){                     log.i(this.getclass().getname(),"error publishing.");                 }else{                     jsonobject graphresponse = response.getgraphobject().getinnerjsonobject();                     string postid = null;                     try {                         postid = graphresponse.getstring("id");                     } catch (jsonexception e) {                         log.i("facebook error", "json error " + e.getmessage());                     }                      //logged in succesfully!                         }             } }); bundle params = request.getparameters(); params.putstring("name", "the title photo."); request.setparameters(params);  request.executeasync(); 

i passing png have in assets folder, can adapt part need. looking @ code should straight forward.