Context.getSystemService() on a null object reference

Issue

Whenever I try to Login in my application this getSystemService() method produce a NPE. pls. help as solutions already available are not answer to my Question. I have called super.oncreate() already.

Stack Trace

Caused by: 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.aiousecurityapplication.Utill.AppConfig.isNetworkAvailable(AppConfig.java:19)
at com.example.aiousecurityapplication.Utill.JSONSenderReceiver.makeHttpRequest(JSONSenderReceiver.java:40)
at com.example.aiousecurityapplication.Activities.SigninActivity$login.doInBackground(SigninActivity.java:200)
at com.example.aiousecurityapplication.Activities.SigninActivity$login.doInBackground(SigninActivity.java:151)
at android.os.AsyncTask$2.call(AsyncTask.java:316)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:255) 
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133) 
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607) 
at java.lang.Thread.run(Thread.java:776) 

Method Location

public class AppConfig {
// Server  url
public static String URL_MAIN = "http://10.14.36.4/aiousecurity/index.php";
public static final String FROM_CNIC = "fromCnic";
public static final String ID = "id";

public static boolean isNetworkAvailable() {

    boolean flag = false;
    ConnectivityManager connMgr =
            (ConnectivityManager) AIOUSecurity.getContext().getSystemService(Context.CONNECTIVITY_SERVICE);
    if (connMgr!= null) {
        NetworkInfo networkInfo= connMgr.getActiveNetworkInfo();
        flag = (networkInfo != null && networkInfo.isConnected());
    }
        return (flag);
}

}

I have also called super.oncreate(); Pls. reference below code

public class AIOUSecurity extends Application {
private static Context context;

public static int screenHeight;
public static int screenWidth;

@Override
public void onCreate() {
    super.onCreate();
    context = getApplicationContext();

    DisplayMetrics displayMetrics = getApplicationContext().getResources().getDisplayMetrics();
    screenHeight = displayMetrics.heightPixels;
    screenWidth = displayMetrics.widthPixels;
}

public static Context getContext() {
    return context;
}

}

Solution

I guess you forget declare application in manifest.

You must add android:name=".AIOUSecurity" into <application> tag of manifest

Answered By - Tung Tran