Java 如何使用接口在两个活动之间进行通信

How to use interface to communicate between two activities

提问by NightFury

I am trying to make listener interface between two activities Act1 and Act2. Act1will start Act2. If there is some event occurred in Act2, it will inform it to Act1. Problem is that I am starting new activity using Intent, so how Act1 will assign itself as listener to Act2's interface?

我正在尝试在两个活动之间制作侦听器界面Act1 and Act2。Act1将开始Act2。如果有什么事件发生Act2，它会通知它Act1。问题是我正在使用 Intent 开始新活动，那么 Act1 如何将自己指定为 Act2 接口的侦听器？

Act1.java

操作1.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

操作2.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);
    }
}

Note:Please don't suggest me to use fragments. I want to use activities currently.

注意：请不要建议我使用片段。我现在想使用活动。

采纳答案by npace

Have you considered using LocalBroadcastManager?

您是否考虑过使用LocalBroadcastManager？

In Act1's onCreate:

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"));

In Act1's onDestroy:

在 Act1 的 onDestroy 中：

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

In Act2's onCreate:

在 Act2 的 onCreate 中：

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

Give me a comment if the code doesn't compile, I'm writing it by hand.

如果代码无法编译，请给我一个评论，我是手工编写的。

回答by vilpe89

I would suggest to create a modelclass. Let me give you an example:

我建议创建一个模型类。让我给你举个例子：

Model class:

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();
    }
}

And here's how you would use this:

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));
    }
}

Changing the member state in second activity:

在第二个活动中更改会员状态：

// Imports
public class SecondActivity extends Activity {

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

---

---

LogCat output:

LogCat 输出：

Current state: false

Current state: false

MainActivity says: Model state changed: true

MainActivity says: Model state changed: true

回答by LEMUEL ADANE

The shorter alternative way is to use static variables, like this:

更短的替代方法是使用静态变量，如下所示：

class Main extends Activity {
  static String msg = "Hi";
}

class Another extends Activity {
  public onCreate() {
     Log.i(Main.msg);
  }
}