Unable to start activity ComponentInfo: java.lang.NullPointerException
<p>i'm building an android application for my degree. i need to get all contacts from phone for 
begin the apllication (later i need also to get emails etcetc). so i used two classes </p>

<p>Degree_thesisActivity</p>

<pre><code>   public class Degree_thesisActivity extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    GetFromPhone gf = new GetFromPhone();
    gf.getContacts();

}
</code></pre>

<p>}</p>

<p>GetFromPhone.java</p>

<pre><code>class GetFromPhone extends Activity {

public void getContacts() {
    // TODO Auto-generated method stub


    /**Declare a Contacts Cursor which have a list of all contacts*/
    Cursor cursor = getContentResolver().query(ContactsContract.Contacts.CONTENT_URI, null, null, null, null);
    /**Move while cursor has another istance to process*/
    while(cursor.moveToNext()){
        /**Get the contact name pointed by cursor at that time*/
        cursor.getString(cursor.getColumnIndex(ContactsContract.Contacts.DISPLAY_NAME));
        String contactID = cursor.getString(cursor.getColumnIndex(ContactsContract.Contacts.DISPLAY_NAME));
        /**show the contact pointed.THIS WILL BE MODIFIED FURTHER!!!!*/
                new AlertDialog.Builder(this)
                    .setMessage(contactID)
                    .setNeutralButton("ok", new OnClickListener() {
                        public void onClick(DialogInterface dialog, int which) {
                            // TODO Auto-generated method stub

                        }
                    })
                    .show();

    }

}
</code></pre>

<p>}</p>

<p>but i get this error :</p>

<p>05-05 15:49:20.060: E/AndroidRuntime(824): java.lang.RuntimeException: Unable to start activity ComponentInfo{it.paki.degreethesis/it.paki.degreethesis.Degree_thesisActivity}: java.lang.NullPointerException</p>

<p>why?anybody can help me?</p>
