JSON Android Error- Attempt to invoke virtual method 'java.lang.String org.json.JSONObject.getString(java.lang.String)' on a null object reference

Question

My app is crashing and the log is showing this error:

Attempt to invoke virtual method 'java.lang.String org.json.JSONObject.getString(java.lang.String)' on a null object reference on the line where I do:

ab = jobj.getString("title");

I'm a noob to Android development. Please help!

public class MainActivity extends ActionBarActivity {

JSONObject jobj = null;
ClientServerInterface clientServerInterface = new ClientServerInterface();
TextView textView;
String ab = "";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    textView = (TextView) findViewById(R.id.textView);
    new RetrieveData().execute();
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings)
    {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

class RetrieveData extends AsyncTask<String,String,String>
{
    protected String doInBackground(String... arg0) {
        jobj = clientServerInterface.makeHttpRequest("http://**.***.***.**/printresult.php");
        try {
            ab = jobj.getString("title");
        } catch (JSONException e) {
            e.printStackTrace();
        }
        return ab;
    }

    protected void onPostExecute(String ab){
        textView.setText(ab);
    }
}
}

Here's the other file:

public class ClientServerInterface {

static InputStream is = null;
static JSONObject jobj = null;
static String json = "";


public ClientServerInterface(){
}
public JSONObject makeHttpRequest(String url){
    DefaultHttpClient httpclient = new DefaultHttpClient();
    HttpPost httppost = new HttpPost(url);
    try{
        HttpResponse httpresponse = httpclient.execute(httppost);
        HttpEntity httpentity = httpresponse.getEntity();
        is = httpentity.getContent();
    }catch (ClientProtocolException e){
        e.printStackTrace();
    }catch (IOException e){
        e.printStackTrace();
    }

    try{
        BufferedReader reader = new BufferedReader(new InputStreamReader(is, "iso-8859-1"), 8);
        StringBuilder sb = new StringBuilder();
        String line = null;
        try{
            while((line = reader.readLine())!= null){
                sb.append(line+"\n");
            }
            is.close();
            json = sb.toString();
            try{
                jobj = new JSONObject(json);
            }catch (JSONException e){
                e.printStackTrace();
            }
        }catch(IOException e){
            e.printStackTrace();
        }
    }catch (UnsupportedEncodingException e){
        e.printStackTrace();
    }
    return jobj;
}
}

Maybe it is in my php file?

<?php
require_once('connection.php');

$qry = "SELECT * FROM eventdetails";
$result = mysql_query($qry);
$rows = array();
while($r = mysql_fetch_assoc($result)){
$rows[] = $r;
}
echo json_encode($rows);
mysql_close();
?>

I'm really stumped. Please help!

GGizmos · Accepted Answer · 2014-12-30 08:50:03Z

3

I believe what's causing the difficulty is that your URL points to a malformed JSON string. What I get at the the URL provided is:

[{"title":"School Start","pictureURL": ...   }]

the Square bracket at the front and at the end should not appear in the string you pass to the JSONObject constructor here.

 json = sb.toString();
        try{
            jobj = new JSONObject(json);
        }catch (JSONException e){
            e.printStackTrace();
        }

You need to trim the first and last character of json since I believe the constructor is throwing an exception which you ar catching and ignoring.

answered Dec 30, 2014 at 8:50

GGizmos

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2 Comments

Kartik Prabhu Over a year ago

Here is what I added: json.substring(1); json.substring(0,json.length()); But I'm still getting that error. But I found something else in the log now. "org.json.JSONException: Value [JSON DATA FROM WEBPAGE] of type org.json.JSONArray cannot be converted to JSONObject"

Kartik Prabhu Over a year ago

I GOT IT THANKS TO YOU!

Baniares · Accepted Answer · 2014-12-30 07:52:59Z

1

try like this

class RetrieveData extends AsyncTask<String,String,JSONObject>{
    protected JSONObject doInBackground(String... arg0) {
        JSONObject jobj = clientServerInterface.makeHttpRequest("http://54.164.136.46/printresult.php");
        return jobj;
    }
    protected void onPostExecute(JSONObject jobj){
        try {
            String ab = jobj.getString("title");
            textView.setText(ab);
        } catch (JSONException e) {
        e.printStackTrace();
        }
    }
}

edited Dec 30, 2014 at 7:52

answered Dec 30, 2014 at 7:42

Baniares

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3 Comments

Kartik Prabhu Over a year ago

Android Studio is giving me an error now. It's saying: Error:(63, 30) error: doInBackground(String...) in MainActivity.RetrieveData cannot override doInBackground(Params...) in AsyncTask return type JSONObject is not compatible with String where Params,Result are type-variables: Params extends Object declared in class AsyncTask Result extends Object declared in class AsyncTask

Kartik Prabhu Over a year ago

Also this one: Error:(62, 5) error: MainActivity.RetrieveData is not abstract and does not override abstract method doInBackground(String...) in AsyncTask

Kartik Prabhu Over a year ago

Oops I mistyped what you wrote. But now it's still giving me that same original error with the null pointer exception

kunal gurnani S · Accepted Answer · 2014-12-30 07:56:23Z

0

this usually is the case with higher version of jdk version set as target . this happen to me when we were using jdk 1.7 as target platform to build with . when changed to jdk 1.5 it resolved the issue . Not sure but it worked.Also to mention that was not specific to android application but was a deployment package . not sure its related but the package was same java.lang.string.

answered Dec 30, 2014 at 7:56

kunal gurnani S

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3 Comments

Kartik Prabhu Over a year ago

Still getting the same null pointer... I changed it in File->Other Settings->Default Settings->Compiler->Java Compiler and tried all the versions

kunal gurnani S Over a year ago

are you using eclipse . then which version is it juno or indigo. check that too . worked on it a very long time ago . try to change platform too if possible. also if possible after changing those try to clean workspace and build again

Kartik Prabhu Over a year ago

I'm on Android Studio. I'll try it on Eclipse

Kartik Prabhu · Accepted Answer · 2014-12-30 16:41:41Z

0

The error, as user1023110 pointed out, happens because the constructor is throwing an exception. In this case, I was giving the constructor a JSONArray and it giving the error that it could not be converted to JSONObject. First, I added this to the top of my ClientServerInterface class:

static JSONArray jarr = null;

Then, I added these two lines:

jarr = new JSONArray(json);
jobj = jarr.getJSONObject(0);

where I previously had this:

jobj = new JSONObject(json);

The method now returns the first JSONObject of the JSONArray.

Thanks to all your help!

answered Dec 30, 2014 at 16:41

Kartik Prabhu

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