LoginDialogFragment.java

/**
 * We have to override setOnShowListener here (min API level 8) in
 * order to validate the inputs before closing the dialog. Just
 * overriding setPositiveButton closes the automatically when the
 * button is pressed
 * 
 * @return The onShowListener for the AlertDialog
 */
@Override
public void onShow(DialogInterface dialog) {
    Button login = ((AlertDialog) dialog)
            .getButton(AlertDialog.BUTTON_POSITIVE);

    login.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            doLogin();
        }
    });
}