NullPointer in codename One

Question

i have some problems with my code with the plugin codename one it tell me that there's a nullpointer exception but the same code work in some other computers so i don't really know where come the problem exact

    Form hi = new Form("Hi World");
    SpanLabel sp = new SpanLabel();
    hi.add(sp);
 hi.show();

    ConnectionRequest con = new ConnectionRequest();
    con.setUrl("http://localhost/pidev2017/select.php");
    con.addResponseListener(new ActionListener<NetworkEvent>() {

        @Override
        public void actionPerformed(NetworkEvent evt) {
            System.out.println(getListEtudiant(new String(con.getResponseData())));
            sp.setText(getListEtudiant(new String(con.getResponseData())) + "");
            hi.refreshTheme();

        }
    });
    NetworkManager.getInstance().addToQueue(con);
}

public ArrayList<Etudiant> getListEtudiant(String json) {
    ArrayList<Etudiant> listEtudiants = new ArrayList<>();

    try {

        JSONParser j = new JSONParser();

        Map<String, Object> etudiants = j.parseJSON(new CharArrayReader(json.toCharArray()));

        System.out.println();
        List<Map<String, Object>> list = (List<Map<String, Object>>) etudiants.get("etudiant");

        for (Map<String, Object> obj : list) {
            Etudiant e = new Etudiant();
            e.setAge(Integer.parseInt(obj.get("age").toString()));
            e.setCin(obj.get("cin").toString());
            e.setNom(obj.get("nom").toString());
            listEtudiants.add(e);

        }

    } catch (IOException ex) {
     }
    return listEtudiants;

}

this is the error i get

java.lang.NullPointerException [EDT] 0:0:0,2 - Expected null for key value while parsing JSON token at row: 2 column: 72 buffer: e1elxde-exe-dlde1ell [EDT] 0:0:0,2 - Expected null for key value while parsing JSON token at row: 2 column: 85 buffer: e1elxde-exe-dlde1ell0elldd [EDT] 0:0:0,2 - Expected true for key value while parsing JSON token at row: 3 column: 2 buffer: e1elxde-exe-dlde1ell0elldd1 [EDT] 0:0:0,2 - Expected true for key value while parsing JSON token at row: 3 column: 3 buffer: e1elxde-exe-dlde1ell0elldd1 [EDT] 0:0:0,2 - Expected null for key value while parsing JSON token at row: 3 column: 7 buffer: e1elxde-exe-dlde1ell0elldd1l [EDT] 0:0:0,2 - Expected true for key value while parsing JSON token at row: 3 column: 10 buffer: e1elxde-exe-dlde1ell0elldd1lef [EDT] 0:0:0,2 - Expected null for key value while parsing JSON token at row: 3 column: 34 buffer: e1elxde-exe-dlde1ell0elldd1leflf57900l

at com.mycompany.myapp.MyApplication.getListEtudiant(MyApplication.java:80)
at com.mycompany.myapp.MyApplication$1.actionPerformed(MyApplication.java:59)
at com.mycompany.myapp.MyApplication$1.actionPerformed(MyApplication.java:55)
at com.codename1.ui.util.EventDispatcher.fireActionSync(EventDispatcher.java:459)
at com.codename1.ui.util.EventDispatcher.access$100(EventDispatcher.java:45)
at com.codename1.ui.util.EventDispatcher$CallbackClass.run(EventDispatcher.java:95)
at com.codename1.ui.Display.processSerialCalls(Display.java:1152)
at com.codename1.ui.Display.edtLoopImpl(Display.java:1096)
at com.codename1.ui.Display.mainEDTLoop(Display.java:997)
at com.codename1.ui.RunnableWrapper.run(RunnableWrapper.java:120)
at com.codename1.impl.CodenameOneThread.run(CodenameOneThread.java:176)

Shai Almog Shai Almog · Accepted Answer · 2017-05-01T04:23:00

As the stack trace says getListEtudiant has a null pointer exception on line 80. Since I can't tell line 80 and have no idea what's the input value I can't give you a more accurate answer but here is the generic one.

Place a breakpoint in the debugger in line 80 when you hit that breakpoint use the inspect variables tool to inspect the various elements and see why that line fails.

Also open the network monitor tool in the simulator and inspect the request/response calls this helps understand where things went wrong.

NullPointer in codename One

1 Answers