辅助类中的View.VISIBLE 和View.INVISIBLE

应用的Activity中有一个布局文件和ProgressBar：

public class Saldo_Menu extends Activity implements OnClickListener, OnLongClickListener {

static InternetHelper IH;
ProgressBar pleasewait;  



    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        pleasewait=(ProgressBar)findViewById(R.id.pleasewait);

        IH=new InternetHelper(this);

        pleasewait.setVisibility(View.INVISIBLE);
}

我想从这个辅助类InternetHelper中激活progressbar，不知道怎么做？ 现在的出现空指针，我知道不能从这里访问UI:

public InternetHelper (Context context) {
        myContext = context;

         }

public void ShowProgressBar(boolean show){
 if (show){pleasewait.setVisibility(View.VISIBLE);}else{pleasewait.setVisibility(View.INVISIBLE);}
}

在helperclass中：

ProgressBar myBar;

public InternetHelper (Context context, ProgressBar pleasewait) {
        myContext = context;
        myBar = pleasewait;
        }

再用ShowProgressBar(boolean)应该就没问题了