Android 相当于 NSNotificationCenter

Question

在将 iPhone 应用程序移植到 android 的过程中，我正在寻找在应用程序内进行通信的最佳方式。 Intent 似乎是要走的路，这是最好的(唯一)选择吗？ NSUserDefaults 在性能和编码方面似乎都比 Intent 轻得多。

我还应该添加我有一个状态的应用程序子类，但我需要让另一个 Activity 知道一个事件。

Answer 1

我找到的最佳等价物是 LocalBroadcastManager这是 Android Support Package 的一部分.

来自 LocalBroadcastManager 文档:

Helper to register for and send broadcasts of Intents to local objects within your process. This is has a number of advantages over sending global broadcasts with sendBroadcast(Intent):

• You know that the data you are broadcasting won't leave your app, so don't need to worry about leaking private data.
• It is not possible for other applications to send these broadcasts to your app, so you don't need to worry about having security holes they can exploit.
• It is more efficient than sending a global broadcast through the system.

使用它时，您可以说 Intent相当于 NSNotification .这是一个例子:

ReceiverActivity.java

监视名为 "custom-event-name" 的事件通知的 Activity .

@Override
public void onCreate(Bundle savedInstanceState) {

  ...
  
  // Register to receive messages.
  // This is just like [[NSNotificationCenter defaultCenter] addObserver:...]
  // We are registering an observer (mMessageReceiver) to receive Intents
  // with actions named "custom-event-name".
  LocalBroadcastManager.getInstance(this).registerReceiver(mMessageReceiver,
      new IntentFilter("custom-event-name"));
}

// Our handler for received Intents. This will be called whenever an Intent
// with an action named "custom-event-name" is broadcasted.
private BroadcastReceiver mMessageReceiver = new BroadcastReceiver() {
  @Override
  public void onReceive(Context context, Intent intent) {
    // Get extra data included in the Intent
    String message = intent.getStringExtra("message");
    Log.d("receiver", "Got message: " + message);
  }
};

@Override
protected void onDestroy() {
  // Unregister since the activity is about to be closed.
  // This is somewhat like [[NSNotificationCenter defaultCenter] removeObserver:name:object:] 
  LocalBroadcastManager.getInstance(this).unregisterReceiver(mMessageReceiver);
  super.onDestroy();
}

SenderActivity.java

发送/广播通知的第二个 Activity 。

@Override
public void onCreate(Bundle savedInstanceState) {
  
  ...
  
  // Every time a button is clicked, we want to broadcast a notification.
  findViewById(R.id.button_send).setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
      sendMessage();
    }
  });
}

// Send an Intent with an action named "custom-event-name". The Intent sent should 
// be received by the ReceiverActivity.
private void sendMessage() {
  Log.d("sender", "Broadcasting message");
  Intent intent = new Intent("custom-event-name");
  // You can also include some extra data.
  intent.putExtra("message", "This is my message!");
  LocalBroadcastManager.getInstance(this).sendBroadcast(intent);
}

使用上面的代码，每次按钮 R.id.button_send被点击，一个 Intent 被广播并被 mMessageReceiver 接收在 ReceiverActivity .

调试输出应如下所示:

01-16 10:35:42.413: D/sender(356): Broadcasting message
01-16 10:35:42.421: D/receiver(356): Got message: This is my message!