Android ContentObserver onChange从未调用

因此，当我更改联系人时，我试图在文本视图中显示我的所有联系人，我希望我的应用程序重新加载包括新联系人在内的联系人。由于某些原因，

onChange（）

从未被调用，即使在我创建了新联系人之后

@Override
public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        outputText = (TextView) findViewById(R.id.textView1);
        outputText.setMaxLines(Integer.MAX_VALUE);
        outputText.setMovementMethod(new ScrollingMovementMethod());
        this.getApplicationContext().getContentResolver().registerContentObserver (ContactsContract.Contacts.CONTENT_URI, true, contentObserver);
        SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
        if(settings.getBoolean("first", true)){
             fetchContacts();
        } else {
             outputText.setText(settings.getString("contacts", "no contacts detected"));
        }
}

public void fetchContacts(){
   // gathers all the contacts
}
public void onPause(){
    super.onPause();
    avePreference();
}

public void savePreference(){
    //code for setting shared preferences
    SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
    SharedPreferences.Editor editor = settings.edit();
    editor.putString("contacts",outputText.getText()+"");
    editor.putBoolean("first", false);
    editor.commit();                    
}

private class ContactObserver extends ContentObserver {

    public ContactObserver() {
        super(null);
    }

    @Override
    public void onChange(boolean selfChange) {
        super.onChange(selfChange);
        fetchContacts();
    }

    @Override
    public boolean deliverSelfNotifications() {
        Log.e("","~~~~~~ Change");
        return true;
    }
}