如何使用接口在两个活动之间进行通信

Question

我正在尝试在两个活动之间创建监听器接口 Act1 and Act2 。 Act1 将开始 Act2 。如果在 Act2 发生了一些事件，它将通知它到 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。我现在想使用活动。

原文由 NightFury 发布，翻译遵循 CC BY-SA 4.0 许可协议

Answer 1

您是否考虑过使用 LocalBroadcastManager ？

在 Act1 的 onCreate 中：

 act2InitReceiver= new BroadcastReceiver()
    {

        @Override
        public void onReceive(Context context, Intent intent)
        {
            // do your listener event stuff
        }
    };
LocalBroadcastManager.getInstance(this).registerReceiver(act2InitReceiver, new IntentFilter("activity-2-initialized"));

在 Act1 的 onDestroy 中：

 LocalBroadcastManager.getInstance(this).unregisterReceiver(act2InitReceiver);

在 Act2 的 onCreate 中：

 LocalBroadcastManager.getInstance(this).sendBroadcast(new Intent("activity-2-initialized"));

如果代码无法编译，请给我评论，我正在手写。

原文由 npace 发布，翻译遵循 CC BY-SA 3.0 许可协议

Answer 2

我建议创建一个 模型 类。让我给你举个例子：

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();
    }
}

以下是您将如何使用它：

 // 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));
    }
}

在第二个活动中更改成员状态：

 // Imports
public class SecondActivity extends Activity {

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

---

日志输出：

Current state: false

MainActivity says: Model state changed: true

原文由 vilpe89 发布，翻译遵循 CC BY-SA 3.0 许可协议