NullPointerException getDefaultSharedPreferences()

Question

I keep getting NullPointerException on this line:

SharedPreferences myPreference = PreferenceManager.getDefaultSharedPreferences(this);

I ran some things through and I believe that I have the wrong context as it is in a subpackage of the main package so I don't think it can reference the XML preference files. I have used this in class's that are in the main package with no trouble but for some reason this causes an exception.

Full code:

package schoolBook.Icestone.Expandable;

import schoolBook.Icestone.Days;
import schoolBook.Icestone.Main;
import schoolBook.Icestone.SetPreference;
import android.content.SharedPreferences;
import android.preference.PreferenceManager;

public class Lesson1 extends Lessons {

    public Lesson1(String name) {
        super(name);
        // setGroup(" " + Days.getLessonarray(0) + " ");
        String key = "W" + Main.getWeek() + "_" + SetPreference.xmlday + "_L"
                + SetPreference.xmllesson + "_Lesson";
        System.out.println(key);
        try {
            SharedPreferences myPreference = PreferenceManager
                    .getDefaultSharedPreferences(this);
            String group = myPreference.getString(key, "def");
            setGroup(" " + group + " ");
        } catch (NullPointerException ex) {
            ex.printStackTrace();
            setGroup(" " + Days.getLessonarray(0) + " ");
        }
    }
}

Lessons class extends Activity so think that may be the source of my problem but im not sure.

File structure:

Icestone

• Main.class and some other classes that use shared preference and it works fine
  • Lessons package (Lesson1 & Lesson are in this package)
• XML folder with the preferences in it

if anyone could help shed some light on this problem it would be much appreciated

Answer 1

You can't do this inside the constructor.

If it extends Activity Class it should't has a constructor, you need to handle that inside the oncreate method.