Null pointer exception when getsystemservices gets called from a class to a fragment

Question

I have a class, which has a method that uses the connectivity manager. This method from this class is called by a fragment to check connectivity. But when I do this, Null pointer exception occurs.

I have tried using getActivity() as context for connection manager, but it didnt help at all. Here is the code:
Class file:

public class Common_Tasks implements AsyncResponse {
int InternetConnectionStatus=-1;
static int MemberShipStatus=-1;

Context ctx;
Common_Tasks(Context context)
{
    this.ctx = context;
}

public void ShowMessage(String msg)
{
    Toast.makeText(ctx,msg,Toast.LENGTH_SHORT).show();
}


public int CheckInternetConnectivity(){
    ConnectivityManager connectivityManager = (ConnectivityManager) ctx.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
    if(networkInfo!=null && networkInfo.isConnected()){
        InternetConnectionStatus=1;
    }
    else {
        InternetConnectionStatus=0;
    }
    return InternetConnectionStatus;
}

public void StartAsyncActivity()
{
    BackgroundTask backgroundTask = new BackgroundTask();
    backgroundTask.delegate = this;
    backgroundTask.execute();
}

@Override
public void processFinish(String output) {
    if(output.equals("true"))
        MemberShipStatus=1;
    else if(output.equals("false"))
        MemberShipStatus=0;
}
}

Fragment:

public class NoInternetConnection extends Fragment {
Common_Tasks commonTasks = new Common_Tasks(getActivity());

public NoInternetConnection() {

}


@Override
public View onCreateView(LayoutInflater inflater, final ViewGroup container,
                         Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_nointernet, container, false);

    final SwipeRefreshLayout swipeRefreshLayout = (SwipeRefreshLayout) view.findViewById(R.id.swipe_id);
    swipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
        @Override
        public void onRefresh() {
            swipeRefreshLayout.setRefreshing(true);
            Handler handler = new Handler(Looper.getMainLooper());
            Runnable r = new Runnable() {
                @Override
                public void run() {
                    swipeRefreshLayout.setRefreshing(false);
                    if(commonTasks.CheckInternetConnectivity()==1)
                        commonTasks.ShowMessage("Internet connection restored!");
                    else
                        commonTasks.ShowMessage("No Internet connection");
                }
            };
            handler.postDelayed(r, 1500);
        }
    });

    return view;
}

}

Error Log:

    09-15 17:09:18.209 16400-16400/com.example.tonymathew.eliteenglishclub E/AndroidRuntime: FATAL EXCEPTION: main
                                                                                         Process: com.example.tonymathew.eliteenglishclub, PID: 16400
                                                                                         java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object android.content.Context.getSystemService(java.lang.String)' on a null object reference
                                                                                             at com.example.tonymathew.eliteenglishclub.Common_Tasks.CheckInternetConnectivity(Common_Tasks.java:25)
                                                                                             at com.example.tonymathew.eliteenglishclub.NoInternetConnection$1$1.run(NoInternetConnection.java:37)
                                                                                             at android.os.Handler.handleCallback(Handler.java:746)
                                                                                             at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                                             at android.os.Looper.loop(Looper.java:148)
                                                                                             at android.app.ActivityThread.main(ActivityThread.java:5443)
                                                                                             at java.lang.reflect.Method.invoke(Native Method)
                                                                                             at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:728)
                                                                                             at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
09-15 17:14:11.634 19927-19927/com.example.tonymathew.eliteenglishclub E/AndroidRuntime: FATAL EXCEPTION: main
                                                                                         Process: com.example.tonymathew.eliteenglishclub, PID: 19927
                                                                                         java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object android.content.Context.getSystemService(java.lang.String)' on a null object reference
                                                                                             at com.example.tonymathew.eliteenglishclub.Common_Tasks.CheckInternetConnectivity(Common_Tasks.java:25)
                                                                                             at com.example.tonymathew.eliteenglishclub.NoInternetConnection$1$1.run(NoInternetConnection.java:37)
                                                                                             at android.os.Handler.handleCallback(Handler.java:746)
                                                                                             at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                                             at android.os.Looper.loop(Looper.java:148)
                                                                                             at android.app.ActivityThread.main(ActivityThread.java:5443)
                                                                                             at java.lang.reflect.Method.invoke(Native Method)
                                                                                             at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:728)
                                                                                             at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)

score 0 · Accepted Answer · answered Sep 15 '16 at 12:01

0

You have to respect the android lifecycle. This is a common issue for android beginners. You can not put this here

public class NoInternetConnection extends Fragment {
Common_Tasks commonTasks = new Common_Tasks(getActivity());

Since the Fragment at this point is not attached to the Activity. Put that into the onCreate() method of your Fragment. For future references see the android lifecycle

answered Sep 15 '16 at 12:01

Murat Karagöz

35,401
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It did work! Thank you. – Tony Mathew Sep 15 '16 at 13:23

score 0 · Answer 2 · answered Sep 15 '16 at 12:01

    public class NoInternetConnection extends Fragment {
    Common_Tasks commonTasks;

    public NoInternetConnection() {

    }


    @Override
    public View onCreateView(LayoutInflater inflater, final ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_nointernet, container, false);
        commonTasks = new Common_Tasks(getActivity());

}

Null pointer exception when getsystemservices gets called from a class to a fragment

2 Answers2