我试图在两个活动之间建立监听器接口Act1 and Act2。Act1将开始Act2。如果发生了某些事件Act2，它将通知它Act1。问题是我正在使用Intent开始新活动，那么Act1如何将自己分配为Act2接口的侦听器？

Act1.java

public class Act1 extends ActionBarActivity implements
        ActionBar.OnNavigationListener {

    ActionBar actionbar;
    Intent pizzaIntent;
    boolean visibleFirstTime = true;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.menutab);

        //set actionbar here
    }

@Override
    public boolean onNavigationItemSelected(int arg0, long arg1)// item pos,
                                                                // itemid
    {
        switch (arg0) {
        case 0:
            if(this.visibleFirstTime == false)
            {
            if(pizzaIntent == null)
            {
                pizzaIntent = new Intent(this,Act2.class);
                //how to call setChangeListener?
            }
            startActivity(pizzaIntent);
            }
            else
                this.visibleFirstTime = false;
            break;
        case 1:
            System.out.println("selected: " + arg0);
            break;
        case 2:
            System.out.println("selected: " + arg0);
            break;
        case 3:
            System.out.println("selected: " + arg0);
            break;
        default:
            break;
        }
        return true;
    }
}

Act2.java

public class Act2 extends Activity {

     selectionChangeListener listener;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.pizza_slice_selection);
    }

    public void setChangeListener(selectionChangeListener listener)
    {
        this.listener = listener;
    }

    private interface selectionChangeListener
    {
        public void selectionMadeAtIndex(int index);
    }
}

注意： 请不要建议我使用片段。我现在要使用活动。