Question

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    String test =  Util.imei();
}


import android.content.Context;
import android.telephony.TelephonyManager;

public class Util{
    Context context;

    public Util(Context context) {
        this.context = context;
    }

    public String imei() {
        TelephonyManager telephonyManager = (TelephonyManager) context
                .getSystemService(Context.TELEPHONY_SERVICE);
        return telephonyManager.getDeviceId();
    }
}

Getting error “Cannot make a static reference to the non-static method imei() from the type Util”.
If I change the line to:

public static String imei() {
    ...
    static Context context;

I get an error and crash app.(“E/AndroidRuntime(629): Caused by:java.lang.NullPointerException”)

Answer 1

two ways to write it:

1st non static

public class Util {
    Context context;

    public Util(Context context) {
        this.context = context;
    }

    public String imei() {
        TelephonyManager telephonyManager = (TelephonyManager) context
                .getSystemService(Context.TELEPHONY_SERVICE);
        return telephonyManager.getDeviceId();
    }
}

and then in onCreate method

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Util u = new Util(this);
    String test =  u.imei();
}

2nd static

public class Util {
    public static String imei(Context context) {
        TelephonyManager telephonyManager = (TelephonyManager) context
                .getSystemService(Context.TELEPHONY_SERVICE);
        return telephonyManager.getDeviceId();
    }
}

and then in onCreate method

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    String test =  Util.imei(this);
}