java - 如何使用接口(interface)在两个 Activity 之间进行通信

Question

我正在尝试在两个 Activity Act1 和 Act2 之间创建监听器接口(interface)。 Act1 将启动 Act2。如果Act2中发生了一些事件，它会通知Act1。问题是我正在使用 Intent 开始新的 Activity ，那么 Act1 将如何将自己分配为 Act2 接口(interface)的监听器？

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 fragment 。我目前想使用 Activity 。

Answer 1

我建议创建一个 model类(class)。举个例子吧:

模型类:

public class CustomModel {

    public interface OnCustomStateListener {
        void stateChanged();
    }

    private static CustomModel mInstance;
    private OnCustomStateListener mListener;
    private boolean mState;

    private CustomModel() {}

    public static CustomModel getInstance() {
        if(mInstance == null) {
            mInstance = new CustomModel();
        }
        return mInstance;
    }

    public void setListener(OnCustomStateListener listener) {
        mListener = listener;
    }

    public void changeState(boolean state) {
        if(mListener != null) {
            mState = state;
            notifyStateChange();
        }
    }

    public boolean getState() {
        return mState;
    }

    private void notifyStateChange() {
        mListener.stateChanged();
    }
}

你将如何使用它:

// Imports
public class MainActivity extends Activity implements OnCustomStateListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        CustomModel.getInstance().setListener(this);

        boolean modelState = CustomModel.getInstance().getState();
        Log.d(TAG, "Current state: " + String.valueOf(modelState));

        Intent intent = new Intent(this, SecondActivity.class);
        startActivity(intent);
    }

    @Override
    public void stateChanged() {
        boolean modelState = CustomModel.getInstance().getState();
        Log.d(TAG, "MainActivity says: Model state changed: " + 
            String.valueOf(modelState));
    }
}

在第二个 Activity 中更改成员(member)状态:

// Imports
public class SecondActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        CustomModel.getInstance().changeState(true);
    }
}

---

LogCat 输出:

当前状态:假

MainActivity 说:模型状态已更改:true