java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Class java.lang.Object.getClass()' on a null object reference

Question

I am trying to envelop my data(Longitude, Latititude, route,timeStamp) in JSON format with the help of GSON library to be sent to the server after 60 seconds. At the moment I am getting the following error java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Class java.lang.Object.getClass()' on a null object reference. I am getting these variables(pLong,pLat, route, formatted) displayed in the xml file.

I appreciate any help.

Error:

04-21 23:15:02.893: E/AndroidRuntime(685): FATAL EXCEPTION: main
04-21 23:15:02.893: E/AndroidRuntime(685): Process: com.bustracker, PID: 685
04-21 23:15:02.893: E/AndroidRuntime(685): java.lang.RuntimeException: Error receiving broadcast Intent { act=android.net.wifi.SCAN_RESULTS flg=0x4000010 } in com.bustracker.MainActivity$BroadcastReceiverListener@2d9405c7
04-21 23:15:02.893: E/AndroidRuntime(685):  at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:933)
04-21 23:15:02.893: E/AndroidRuntime(685):  at android.os.Handler.handleCallback(Handler.java:739)
04-21 23:15:02.893: E/AndroidRuntime(685):  at android.os.Handler.dispatchMessage(Handler.java:95)
04-21 23:15:02.893: E/AndroidRuntime(685):  at android.os.Looper.loop(Looper.java:145)
04-21 23:15:02.893: E/AndroidRuntime(685):  at android.app.ActivityThread.main(ActivityThread.java:5944)
04-21 23:15:02.893: E/AndroidRuntime(685):  at java.lang.reflect.Method.invoke(Native Method)
04-21 23:15:02.893: E/AndroidRuntime(685):  at java.lang.reflect.Method.invoke(Method.java:372)
04-21 23:15:02.893: E/AndroidRuntime(685):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1389)
04-21 23:15:02.893: E/AndroidRuntime(685):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1184)
04-21 23:15:02.893: E/AndroidRuntime(685): Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'java.util.Iterator java.util.List.iterator()' on a null object reference
04-21 23:15:02.893: E/AndroidRuntime(685):  at com.bustracker.MainActivity$BroadcastReceiverListener.parse_SSID(MainActivity.java:218)
04-21 23:15:02.893: E/AndroidRuntime(685):  at com.bustracker.MainActivity$BroadcastReceiverListener.onReceive(MainActivity.java:172)
04-21 23:15:02.893: E/AndroidRuntime(685):  at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:923)
04-21 23:15:02.893: E/AndroidRuntime(685):  ... 8 more

Data class:

public class Data {
    double longitude;
    double latitude;
    //int speed;
    String time;
    int route;

    public Data(double longitude, double latitude, String time,
            int route) {
        super();
        this.longitude = longitude;
        latitude = latitude;
        //this.speed = speed;
        this.time = time;
        this.route = route;
    }

    public double getLongitude() {
        return longitude;
    }

    public void setLongitude(double longitude) {
        this.longitude = longitude;
    }

    public double getLatitude() {
        return latitude;
    }

    public void setLatitude(double latitude) {
        latitude = latitude;
    }

//  public int getSpeed() {
//      return speed;
//  }
//
//  public void setSpeed(int speed) {
//      this.speed = speed;
//  }

    public String getTime() {
        return time;
    }

    public void setTime(String time) {
        this.time = time;
    }

    public int getRoute() {
        return route;
    }

    public void setRoute(int route) {
        this.route = route;
    }

}

DataSerializer class:

import java.lang.reflect.Type;

import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonPrimitive;
import com.google.gson.JsonSerializationContext;
import com.google.gson.JsonSerializer;

public class DataSerializer implements JsonSerializer<Data> {

    @Override
    public JsonElement serialize(Data data, Type arg1,
            JsonSerializationContext arg2) {
         JsonObject result = new JsonObject();
         result.add("longitude", new JsonPrimitive(data.getLongitude()));
         result.add("latitude", new JsonPrimitive(data.getLatitude()));
        // result.add("speed", new JsonPrimitive(data.getSpeed()));
         result.add("formatted", new JsonPrimitive(data.getTime()));
         result.add("route", new JsonPrimitive(data.getRoute()));
        return result;
    }

}

This part is in the MainActivity:

public class MainActivity extends ActionBarActivity {
    double pLong;
    double pLat;
    String formatted;
    int route_number;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Data d = new Data(pLong, pLat, formatted,route_number);
        Gson gson = new GsonBuilder().registerTypeAdapter(Data.class, new DataSerializer()).create();
        System.out.println(gson.toJson(d));
  }
}

Could you add a command to line 79 (at the onCreate method)? — moffeltje
– moffeltje, Commented Apr 21, 2015 at 21:04
@moffeltje: that is this line"System.out.println(gson.toJson(d));" in the onCreate method. — Mr Asker
– Mr Asker, Commented Apr 21, 2015 at 21:07

Divers · Accepted Answer · 2015-04-21 21:08:26Z

3

Your time variable is null. You should initialize it in case if you put it in JsonObject in your DataSerializer

formatted = "13.10.2015";
Data d = new Data(pLong, pLat, formatted,route_number);

answered Apr 21, 2015 at 21:08

Divers

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1 Comment

Mr Asker Over a year ago

The problem was I forgot to turn the GPS on since the time is being created in the onLocationChanged method location.getTime() but I am getting now the following error: "Attempt to invoke interface method 'java.util.Iterator java.util.List.iterator()' on a null object reference" I have changed the trace error.

Zelldon · Accepted Answer · 2015-04-21 21:10:44Z

0

You create the following data object:

Data d = new Data(pLong, pLat, formatted,route_number);

Are you sure that the variable formatted is not null?

Because the exception appears after you add

result.add("formatted", new JsonPrimitive(data.getTime()));

that means your data.getTime() returns a null value and puts these null value into the json object which throws a nullpointer exception.

So either check the value before adding the value or initialize the value correctly.

answered Apr 21, 2015 at 21:10

Zelldon

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