Afficher une boite de dialogue sous Android

Bonjour
Voici un exemple pour afficher une boite de dialogue sous Android:

public class DialogActivity extends FragmentActivity {
public static final int TYPE_DIALOG_FRAGMENT = 1;
public static final int TYPE_ALERT_DIALOG = 2;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_dialog);
}

protected void showDialogType(int type) {
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
Fragment prev = getSupportFragmentManager().findFragmentByTag("dialog");
if (prev != null) {
ft.remove(prev);
}
ft.addToBackStack(null);

DialogFragment newFragment = null;
switch (type) {
case TYPE_DIALOG_FRAGMENT:
newFragment = MyDialogFragment
.newInstance(R.string.title_fragment_dialog);
break;
case TYPE_ALERT_DIALOG:
newFragment = MyAlertDialog
.newInstance(R.string.title_fragment_dialog_alert);
break;
}
newFragment.show(ft, "dialog");
}

public void showDialogFragment(View v) {
showDialogType(TYPE_DIALOG_FRAGMENT);
}

public void showAlertDialog(View v) {
showDialogType(TYPE_ALERT_DIALOG);
}

public void doPositiveClick() {
// TODO Do something
}

public void doNegativeClick() {
// TODO Do something
}
}