Java.lang.NullPointerException: Attempting to call virtual method 'java.lang.Class java.lang.Object.getClass ()' on a null object reference
I am trying to pass my data (longitude, labitut, route, time) in JSON format using the GSON library, which will be sent to the server in 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 an XML file.
I appreciate any help.
Mistake:
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 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));
}
}
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The following data object is created:
Data d = new Data(pLong, pLat, formatted,route_number);
Are you sure the variable is formatted
not null?
Since the exception appears after adding
result.add("formatted", new JsonPrimitive(data.getTime()));
this means your data.getTime () returns null and puts those null values ββinto a json object which throws a nullpointer exception.
So, either check the value before adding the value or initialize the value correctly.
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