将数据从服务传递到当前活动

Question

我正在构建一个使用GCM来推送消息和通知的聊天应用程序.

在应用程序中,我有一个活动,列出会话线程(ConversationListActivity)和一个活动,显示线程内的对话(ConversationActivity).

我在GCMIntentService的onMessage方法中捕获新消息.通知有效,消息按预期记录.

public class GCMIntentService extends GCMBaseIntentService {
  @Override
  protected void onMessage(Context context, Intent intent) {
    Bundle extras = intent.getExtras();
    String sender = extras.getString("sender");
    String message = extras.getString("message");

    ConversationModel model = new ConversationModel(context);
    model.open();
    model.createMessage(sender, message.trim(), true, true, ConversationMessage.STATUS_SENT);
    model.close();

    this.createMessageNotification(context, sender, message);
  }
}

问题是,如果GCM在ConversationActivity激活时推送新消息,我不希望它生成通知.相反,我希望对话直接刷新.

ConversationActivity每次有来自GCM的新消息时,如何让主动刷新消息列表？

Answer 1

我自己找到了解决方案.我确信这不是最好的方法,但至少它对我有用.

创建一个派生Handler用于存储活动的单例类ConversationActivity.在该handleMessage方法中,处理将从服务调度的消息,该消息告诉处理程序告诉活动刷新对话.

public class ActiveMessageHandler extends Handler {

  private static ActiveMessageHandler _instance = new ActiveMessageHandler();
  private Activity _activity = null;

  @Override
  public void handleMessage(Message message) {
    if(message.obj.toString().equals("gcmNewMessage") && _activity != null)
        ((ConversationActivity)_activity).repopulateList();

    super.handleMessage(message);
  }

  public static ActiveMessageHandler instance() {
    return _instance;
  }

  public void setActivity(Activity activity) {
    _activity = activity;
  }

  public Activity getActivity() {
    return _activity;
  }

}

然后,在ConversationActivity,在处理程序中设置activity属性.

public class ConversationActivity extends Activity {
  @Override
  public void onStart() {
    super.onStart();
    ActiveMessageHandler.instance().setActivity(this);
  }

  @Override
  public void onStop() {
    super.onStop();
    ActiveMessageHandler.instance().setActivity(null);
  }
}

最后,在服务中,检查处理程序中的活动是否为空,并向处理程序发送消息以刷新对话.

public class GCMIntentService extends GCMBaseIntentService {
    @Override
    protected void onMessage(Context context, Intent intent) {
        Bundle extras = intent.getExtras();
        String sender = extras.getString("sender");
        String message = extras.getString("message");

        ConversationModel model = new ConversationModel(context);
        model.open();
        model.createMessage(sender, message.trim(), true, true, ConversationMessage.STATUS_SENT);
        model.close();

        // if ConversationActivity is active, send a message to handler to refresh the conversation
        if(ActiveMessageHandler.instance().getActivity() != null)
        {
            Message msg = Message.obtain(ActiveMessageHandler.instance());
            msg.obj = "gcmNewMessage";
            ActiveMessageHandler.instance().sendMessage(msg);

            // Optionally, play a notification sound
            Uri notification = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
            Ringtone r = RingtoneManager.getRingtone(getApplicationContext(), notification);
            r.play();
        }
        else
            createMessageNotification(context, sender, message);
    }
}