How to refer to a macro component?

public class MyWindow extends Window implements AfterCompose{
    private Listbox listbox;
    private MyComp myComp;  // macro component


    public void onCreate$myWindow() {
      String str = myComp.getId();  // myComp is null;
    }
}

<window id="myComp" use="MyComp">
	<textbox id="tbName" value="@{myObj.name}" width="300px"/>
</window>

public class MyComp extends Window {

    private MyObj myObj;


    public MyObj getMyobj() {
        return myObj;
    }

    public void setMyobj(MyObj myObj) {
        this.myObj = myObj;
    }

    public void onCreate$myComp() {
        myObj = new MyObj();
    }
}